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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:46:48 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:46:48 +0000
commit311bcfc6b3acdd6fd152798c7f287ddf74fa2a98 (patch)
tree0ec307299b1dada3701e42f4ca6eda57d708261e /src/backend/access/transam/xlog.c
parentInitial commit. (diff)
downloadpostgresql-15-upstream.tar.xz
postgresql-15-upstream.zip
Adding upstream version 15.4.upstream/15.4upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+/*-------------------------------------------------------------------------
+ *
+ * xlog.c
+ * PostgreSQL write-ahead log manager
+ *
+ * The Write-Ahead Log (WAL) functionality is split into several source
+ * files, in addition to this one:
+ *
+ * xloginsert.c - Functions for constructing WAL records
+ * xlogrecovery.c - WAL recovery and standby code
+ * xlogreader.c - Facility for reading WAL files and parsing WAL records
+ * xlogutils.c - Helper functions for WAL redo routines
+ *
+ * This file contains functions for coordinating database startup and
+ * checkpointing, and managing the write-ahead log buffers when the
+ * system is running.
+ *
+ * StartupXLOG() is the main entry point of the startup process. It
+ * coordinates database startup, performing WAL recovery, and the
+ * transition from WAL recovery into normal operations.
+ *
+ * XLogInsertRecord() inserts a WAL record into the WAL buffers. Most
+ * callers should not call this directly, but use the functions in
+ * xloginsert.c to construct the WAL record. XLogFlush() can be used
+ * to force the WAL to disk.
+ *
+ * In addition to those, there are many other functions for interrogating
+ * the current system state, and for starting/stopping backups.
+ *
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/backend/access/transam/xlog.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include <ctype.h>
+#include <math.h>
+#include <time.h>
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <unistd.h>
+
+#include "access/clog.h"
+#include "access/commit_ts.h"
+#include "access/heaptoast.h"
+#include "access/multixact.h"
+#include "access/rewriteheap.h"
+#include "access/subtrans.h"
+#include "access/timeline.h"
+#include "access/transam.h"
+#include "access/twophase.h"
+#include "access/xact.h"
+#include "access/xlog_internal.h"
+#include "access/xlogarchive.h"
+#include "access/xloginsert.h"
+#include "access/xlogprefetcher.h"
+#include "access/xlogreader.h"
+#include "access/xlogrecovery.h"
+#include "access/xlogutils.h"
+#include "backup/basebackup.h"
+#include "catalog/catversion.h"
+#include "catalog/pg_control.h"
+#include "catalog/pg_database.h"
+#include "common/controldata_utils.h"
+#include "common/file_utils.h"
+#include "executor/instrument.h"
+#include "miscadmin.h"
+#include "pg_trace.h"
+#include "pgstat.h"
+#include "port/atomics.h"
+#include "port/pg_iovec.h"
+#include "postmaster/bgwriter.h"
+#include "postmaster/startup.h"
+#include "postmaster/walwriter.h"
+#include "replication/logical.h"
+#include "replication/origin.h"
+#include "replication/slot.h"
+#include "replication/snapbuild.h"
+#include "replication/walreceiver.h"
+#include "replication/walsender.h"
+#include "storage/bufmgr.h"
+#include "storage/fd.h"
+#include "storage/ipc.h"
+#include "storage/large_object.h"
+#include "storage/latch.h"
+#include "storage/pmsignal.h"
+#include "storage/predicate.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
+#include "storage/reinit.h"
+#include "storage/smgr.h"
+#include "storage/spin.h"
+#include "storage/sync.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+#include "utils/ps_status.h"
+#include "utils/relmapper.h"
+#include "utils/pg_rusage.h"
+#include "utils/snapmgr.h"
+#include "utils/timeout.h"
+#include "utils/timestamp.h"
+
+extern uint32 bootstrap_data_checksum_version;
+
+/* timeline ID to be used when bootstrapping */
+#define BootstrapTimeLineID 1
+
+/* User-settable parameters */
+int max_wal_size_mb = 1024; /* 1 GB */
+int min_wal_size_mb = 80; /* 80 MB */
+int wal_keep_size_mb = 0;
+int XLOGbuffers = -1;
+int XLogArchiveTimeout = 0;
+int XLogArchiveMode = ARCHIVE_MODE_OFF;
+char *XLogArchiveCommand = NULL;
+bool EnableHotStandby = false;
+bool fullPageWrites = true;
+bool wal_log_hints = false;
+int wal_compression = WAL_COMPRESSION_NONE;
+char *wal_consistency_checking_string = NULL;
+bool *wal_consistency_checking = NULL;
+bool wal_init_zero = true;
+bool wal_recycle = true;
+bool log_checkpoints = true;
+int sync_method = DEFAULT_SYNC_METHOD;
+int wal_level = WAL_LEVEL_MINIMAL;
+int CommitDelay = 0; /* precommit delay in microseconds */
+int CommitSiblings = 5; /* # concurrent xacts needed to sleep */
+int wal_retrieve_retry_interval = 5000;
+int max_slot_wal_keep_size_mb = -1;
+int wal_decode_buffer_size = 512 * 1024;
+bool track_wal_io_timing = false;
+
+#ifdef WAL_DEBUG
+bool XLOG_DEBUG = false;
+#endif
+
+int wal_segment_size = DEFAULT_XLOG_SEG_SIZE;
+
+/*
+ * Number of WAL insertion locks to use. A higher value allows more insertions
+ * to happen concurrently, but adds some CPU overhead to flushing the WAL,
+ * which needs to iterate all the locks.
+ */
+#define NUM_XLOGINSERT_LOCKS 8
+
+/*
+ * Max distance from last checkpoint, before triggering a new xlog-based
+ * checkpoint.
+ */
+int CheckPointSegments;
+
+/* Estimated distance between checkpoints, in bytes */
+static double CheckPointDistanceEstimate = 0;
+static double PrevCheckPointDistance = 0;
+
+/*
+ * GUC support
+ */
+const struct config_enum_entry sync_method_options[] = {
+ {"fsync", SYNC_METHOD_FSYNC, false},
+#ifdef HAVE_FSYNC_WRITETHROUGH
+ {"fsync_writethrough", SYNC_METHOD_FSYNC_WRITETHROUGH, false},
+#endif
+#ifdef HAVE_FDATASYNC
+ {"fdatasync", SYNC_METHOD_FDATASYNC, false},
+#endif
+#ifdef OPEN_SYNC_FLAG
+ {"open_sync", SYNC_METHOD_OPEN, false},
+#endif
+#ifdef OPEN_DATASYNC_FLAG
+ {"open_datasync", SYNC_METHOD_OPEN_DSYNC, false},
+#endif
+ {NULL, 0, false}
+};
+
+
+/*
+ * Although only "on", "off", and "always" are documented,
+ * we accept all the likely variants of "on" and "off".
+ */
+const struct config_enum_entry archive_mode_options[] = {
+ {"always", ARCHIVE_MODE_ALWAYS, false},
+ {"on", ARCHIVE_MODE_ON, false},
+ {"off", ARCHIVE_MODE_OFF, false},
+ {"true", ARCHIVE_MODE_ON, true},
+ {"false", ARCHIVE_MODE_OFF, true},
+ {"yes", ARCHIVE_MODE_ON, true},
+ {"no", ARCHIVE_MODE_OFF, true},
+ {"1", ARCHIVE_MODE_ON, true},
+ {"0", ARCHIVE_MODE_OFF, true},
+ {NULL, 0, false}
+};
+
+/*
+ * Statistics for current checkpoint are collected in this global struct.
+ * Because only the checkpointer or a stand-alone backend can perform
+ * checkpoints, this will be unused in normal backends.
+ */
+CheckpointStatsData CheckpointStats;
+
+/*
+ * During recovery, lastFullPageWrites keeps track of full_page_writes that
+ * the replayed WAL records indicate. It's initialized with full_page_writes
+ * that the recovery starting checkpoint record indicates, and then updated
+ * each time XLOG_FPW_CHANGE record is replayed.
+ */
+static bool lastFullPageWrites;
+
+/*
+ * Local copy of the state tracked by SharedRecoveryState in shared memory,
+ * It is false if SharedRecoveryState is RECOVERY_STATE_DONE. True actually
+ * means "not known, need to check the shared state".
+ */
+static bool LocalRecoveryInProgress = true;
+
+/*
+ * Local state for XLogInsertAllowed():
+ * 1: unconditionally allowed to insert XLOG
+ * 0: unconditionally not allowed to insert XLOG
+ * -1: must check RecoveryInProgress(); disallow until it is false
+ * Most processes start with -1 and transition to 1 after seeing that recovery
+ * is not in progress. But we can also force the value for special cases.
+ * The coding in XLogInsertAllowed() depends on the first two of these states
+ * being numerically the same as bool true and false.
+ */
+static int LocalXLogInsertAllowed = -1;
+
+/*
+ * ProcLastRecPtr points to the start of the last XLOG record inserted by the
+ * current backend. It is updated for all inserts. XactLastRecEnd points to
+ * end+1 of the last record, and is reset when we end a top-level transaction,
+ * or start a new one; so it can be used to tell if the current transaction has
+ * created any XLOG records.
+ *
+ * While in parallel mode, this may not be fully up to date. When committing,
+ * a transaction can assume this covers all xlog records written either by the
+ * user backend or by any parallel worker which was present at any point during
+ * the transaction. But when aborting, or when still in parallel mode, other
+ * parallel backends may have written WAL records at later LSNs than the value
+ * stored here. The parallel leader advances its own copy, when necessary,
+ * in WaitForParallelWorkersToFinish.
+ */
+XLogRecPtr ProcLastRecPtr = InvalidXLogRecPtr;
+XLogRecPtr XactLastRecEnd = InvalidXLogRecPtr;
+XLogRecPtr XactLastCommitEnd = InvalidXLogRecPtr;
+
+/*
+ * RedoRecPtr is this backend's local copy of the REDO record pointer
+ * (which is almost but not quite the same as a pointer to the most recent
+ * CHECKPOINT record). We update this from the shared-memory copy,
+ * XLogCtl->Insert.RedoRecPtr, whenever we can safely do so (ie, when we
+ * hold an insertion lock). See XLogInsertRecord for details. We are also
+ * allowed to update from XLogCtl->RedoRecPtr if we hold the info_lck;
+ * see GetRedoRecPtr.
+ *
+ * NB: Code that uses this variable must be prepared not only for the
+ * possibility that it may be arbitrarily out of date, but also for the
+ * possibility that it might be set to InvalidXLogRecPtr. We used to
+ * initialize it as a side effect of the first call to RecoveryInProgress(),
+ * which meant that most code that might use it could assume that it had a
+ * real if perhaps stale value. That's no longer the case.
+ */
+static XLogRecPtr RedoRecPtr;
+
+/*
+ * doPageWrites is this backend's local copy of (forcePageWrites ||
+ * fullPageWrites). It is used together with RedoRecPtr to decide whether
+ * a full-page image of a page need to be taken.
+ *
+ * NB: Initially this is false, and there's no guarantee that it will be
+ * initialized to any other value before it is first used. Any code that
+ * makes use of it must recheck the value after obtaining a WALInsertLock,
+ * and respond appropriately if it turns out that the previous value wasn't
+ * accurate.
+ */
+static bool doPageWrites;
+
+/*----------
+ * Shared-memory data structures for XLOG control
+ *
+ * LogwrtRqst indicates a byte position that we need to write and/or fsync
+ * the log up to (all records before that point must be written or fsynced).
+ * LogwrtResult indicates the byte positions we have already written/fsynced.
+ * These structs are identical but are declared separately to indicate their
+ * slightly different functions.
+ *
+ * To read XLogCtl->LogwrtResult, you must hold either info_lck or
+ * WALWriteLock. To update it, you need to hold both locks. The point of
+ * this arrangement is that the value can be examined by code that already
+ * holds WALWriteLock without needing to grab info_lck as well. In addition
+ * to the shared variable, each backend has a private copy of LogwrtResult,
+ * which is updated when convenient.
+ *
+ * The request bookkeeping is simpler: there is a shared XLogCtl->LogwrtRqst
+ * (protected by info_lck), but we don't need to cache any copies of it.
+ *
+ * info_lck is only held long enough to read/update the protected variables,
+ * so it's a plain spinlock. The other locks are held longer (potentially
+ * over I/O operations), so we use LWLocks for them. These locks are:
+ *
+ * WALBufMappingLock: must be held to replace a page in the WAL buffer cache.
+ * It is only held while initializing and changing the mapping. If the
+ * contents of the buffer being replaced haven't been written yet, the mapping
+ * lock is released while the write is done, and reacquired afterwards.
+ *
+ * WALWriteLock: must be held to write WAL buffers to disk (XLogWrite or
+ * XLogFlush).
+ *
+ * ControlFileLock: must be held to read/update control file or create
+ * new log file.
+ *
+ *----------
+ */
+
+typedef struct XLogwrtRqst
+{
+ XLogRecPtr Write; /* last byte + 1 to write out */
+ XLogRecPtr Flush; /* last byte + 1 to flush */
+} XLogwrtRqst;
+
+typedef struct XLogwrtResult
+{
+ XLogRecPtr Write; /* last byte + 1 written out */
+ XLogRecPtr Flush; /* last byte + 1 flushed */
+} XLogwrtResult;
+
+/*
+ * Inserting to WAL is protected by a small fixed number of WAL insertion
+ * locks. To insert to the WAL, you must hold one of the locks - it doesn't
+ * matter which one. To lock out other concurrent insertions, you must hold
+ * of them. Each WAL insertion lock consists of a lightweight lock, plus an
+ * indicator of how far the insertion has progressed (insertingAt).
+ *
+ * The insertingAt values are read when a process wants to flush WAL from
+ * the in-memory buffers to disk, to check that all the insertions to the
+ * region the process is about to write out have finished. You could simply
+ * wait for all currently in-progress insertions to finish, but the
+ * insertingAt indicator allows you to ignore insertions to later in the WAL,
+ * so that you only wait for the insertions that are modifying the buffers
+ * you're about to write out.
+ *
+ * This isn't just an optimization. If all the WAL buffers are dirty, an
+ * inserter that's holding a WAL insert lock might need to evict an old WAL
+ * buffer, which requires flushing the WAL. If it's possible for an inserter
+ * to block on another inserter unnecessarily, deadlock can arise when two
+ * inserters holding a WAL insert lock wait for each other to finish their
+ * insertion.
+ *
+ * Small WAL records that don't cross a page boundary never update the value,
+ * the WAL record is just copied to the page and the lock is released. But
+ * to avoid the deadlock-scenario explained above, the indicator is always
+ * updated before sleeping while holding an insertion lock.
+ *
+ * lastImportantAt contains the LSN of the last important WAL record inserted
+ * using a given lock. This value is used to detect if there has been
+ * important WAL activity since the last time some action, like a checkpoint,
+ * was performed - allowing to not repeat the action if not. The LSN is
+ * updated for all insertions, unless the XLOG_MARK_UNIMPORTANT flag was
+ * set. lastImportantAt is never cleared, only overwritten by the LSN of newer
+ * records. Tracking the WAL activity directly in WALInsertLock has the
+ * advantage of not needing any additional locks to update the value.
+ */
+typedef struct
+{
+ LWLock lock;
+ XLogRecPtr insertingAt;
+ XLogRecPtr lastImportantAt;
+} WALInsertLock;
+
+/*
+ * All the WAL insertion locks are allocated as an array in shared memory. We
+ * force the array stride to be a power of 2, which saves a few cycles in
+ * indexing, but more importantly also ensures that individual slots don't
+ * cross cache line boundaries. (Of course, we have to also ensure that the
+ * array start address is suitably aligned.)
+ */
+typedef union WALInsertLockPadded
+{
+ WALInsertLock l;
+ char pad[PG_CACHE_LINE_SIZE];
+} WALInsertLockPadded;
+
+/*
+ * Session status of running backup, used for sanity checks in SQL-callable
+ * functions to start and stop backups.
+ */
+static SessionBackupState sessionBackupState = SESSION_BACKUP_NONE;
+
+/*
+ * Shared state data for WAL insertion.
+ */
+typedef struct XLogCtlInsert
+{
+ slock_t insertpos_lck; /* protects CurrBytePos and PrevBytePos */
+
+ /*
+ * CurrBytePos is the end of reserved WAL. The next record will be
+ * inserted at that position. PrevBytePos is the start position of the
+ * previously inserted (or rather, reserved) record - it is copied to the
+ * prev-link of the next record. These are stored as "usable byte
+ * positions" rather than XLogRecPtrs (see XLogBytePosToRecPtr()).
+ */
+ uint64 CurrBytePos;
+ uint64 PrevBytePos;
+
+ /*
+ * Make sure the above heavily-contended spinlock and byte positions are
+ * on their own cache line. In particular, the RedoRecPtr and full page
+ * write variables below should be on a different cache line. They are
+ * read on every WAL insertion, but updated rarely, and we don't want
+ * those reads to steal the cache line containing Curr/PrevBytePos.
+ */
+ char pad[PG_CACHE_LINE_SIZE];
+
+ /*
+ * fullPageWrites is the authoritative value used by all backends to
+ * determine whether to write full-page image to WAL. This shared value,
+ * instead of the process-local fullPageWrites, is required because, when
+ * full_page_writes is changed by SIGHUP, we must WAL-log it before it
+ * actually affects WAL-logging by backends. Checkpointer sets at startup
+ * or after SIGHUP.
+ *
+ * To read these fields, you must hold an insertion lock. To modify them,
+ * you must hold ALL the locks.
+ */
+ XLogRecPtr RedoRecPtr; /* current redo point for insertions */
+ bool forcePageWrites; /* forcing full-page writes for PITR? */
+ bool fullPageWrites;
+
+ /*
+ * runningBackups is a counter indicating the number of backups currently
+ * in progress. forcePageWrites is set to true when runningBackups is
+ * non-zero. lastBackupStart is the latest checkpoint redo location used
+ * as a starting point for an online backup.
+ */
+ int runningBackups;
+ XLogRecPtr lastBackupStart;
+
+ /*
+ * WAL insertion locks.
+ */
+ WALInsertLockPadded *WALInsertLocks;
+} XLogCtlInsert;
+
+/*
+ * Total shared-memory state for XLOG.
+ */
+typedef struct XLogCtlData
+{
+ XLogCtlInsert Insert;
+
+ /* Protected by info_lck: */
+ XLogwrtRqst LogwrtRqst;
+ XLogRecPtr RedoRecPtr; /* a recent copy of Insert->RedoRecPtr */
+ FullTransactionId ckptFullXid; /* nextXid of latest checkpoint */
+ XLogRecPtr asyncXactLSN; /* LSN of newest async commit/abort */
+ XLogRecPtr replicationSlotMinLSN; /* oldest LSN needed by any slot */
+
+ XLogSegNo lastRemovedSegNo; /* latest removed/recycled XLOG segment */
+
+ /* Fake LSN counter, for unlogged relations. Protected by ulsn_lck. */
+ XLogRecPtr unloggedLSN;
+ slock_t ulsn_lck;
+
+ /* Time and LSN of last xlog segment switch. Protected by WALWriteLock. */
+ pg_time_t lastSegSwitchTime;
+ XLogRecPtr lastSegSwitchLSN;
+
+ /*
+ * Protected by info_lck and WALWriteLock (you must hold either lock to
+ * read it, but both to update)
+ */
+ XLogwrtResult LogwrtResult;
+
+ /*
+ * Latest initialized page in the cache (last byte position + 1).
+ *
+ * To change the identity of a buffer (and InitializedUpTo), you need to
+ * hold WALBufMappingLock. To change the identity of a buffer that's
+ * still dirty, the old page needs to be written out first, and for that
+ * you need WALWriteLock, and you need to ensure that there are no
+ * in-progress insertions to the page by calling
+ * WaitXLogInsertionsToFinish().
+ */
+ XLogRecPtr InitializedUpTo;
+
+ /*
+ * These values do not change after startup, although the pointed-to pages
+ * and xlblocks values certainly do. xlblocks values are protected by
+ * WALBufMappingLock.
+ */
+ char *pages; /* buffers for unwritten XLOG pages */
+ XLogRecPtr *xlblocks; /* 1st byte ptr-s + XLOG_BLCKSZ */
+ int XLogCacheBlck; /* highest allocated xlog buffer index */
+
+ /*
+ * InsertTimeLineID is the timeline into which new WAL is being inserted
+ * and flushed. It is zero during recovery, and does not change once set.
+ *
+ * If we create a new timeline when the system was started up,
+ * PrevTimeLineID is the old timeline's ID that we forked off from.
+ * Otherwise it's equal to InsertTimeLineID.
+ */
+ TimeLineID InsertTimeLineID;
+ TimeLineID PrevTimeLineID;
+
+ /*
+ * SharedRecoveryState indicates if we're still in crash or archive
+ * recovery. Protected by info_lck.
+ */
+ RecoveryState SharedRecoveryState;
+
+ /*
+ * InstallXLogFileSegmentActive indicates whether the checkpointer should
+ * arrange for future segments by recycling and/or PreallocXlogFiles().
+ * Protected by ControlFileLock. Only the startup process changes it. If
+ * true, anyone can use InstallXLogFileSegment(). If false, the startup
+ * process owns the exclusive right to install segments, by reading from
+ * the archive and possibly replacing existing files.
+ */
+ bool InstallXLogFileSegmentActive;
+
+ /*
+ * WalWriterSleeping indicates whether the WAL writer is currently in
+ * low-power mode (and hence should be nudged if an async commit occurs).
+ * Protected by info_lck.
+ */
+ bool WalWriterSleeping;
+
+ /*
+ * During recovery, we keep a copy of the latest checkpoint record here.
+ * lastCheckPointRecPtr points to start of checkpoint record and
+ * lastCheckPointEndPtr points to end+1 of checkpoint record. Used by the
+ * checkpointer when it wants to create a restartpoint.
+ *
+ * Protected by info_lck.
+ */
+ XLogRecPtr lastCheckPointRecPtr;
+ XLogRecPtr lastCheckPointEndPtr;
+ CheckPoint lastCheckPoint;
+
+ /*
+ * lastFpwDisableRecPtr points to the start of the last replayed
+ * XLOG_FPW_CHANGE record that instructs full_page_writes is disabled.
+ */
+ XLogRecPtr lastFpwDisableRecPtr;
+
+ slock_t info_lck; /* locks shared variables shown above */
+} XLogCtlData;
+
+static XLogCtlData *XLogCtl = NULL;
+
+/* a private copy of XLogCtl->Insert.WALInsertLocks, for convenience */
+static WALInsertLockPadded *WALInsertLocks = NULL;
+
+/*
+ * We maintain an image of pg_control in shared memory.
+ */
+static ControlFileData *ControlFile = NULL;
+
+/*
+ * Calculate the amount of space left on the page after 'endptr'. Beware
+ * multiple evaluation!
+ */
+#define INSERT_FREESPACE(endptr) \
+ (((endptr) % XLOG_BLCKSZ == 0) ? 0 : (XLOG_BLCKSZ - (endptr) % XLOG_BLCKSZ))
+
+/* Macro to advance to next buffer index. */
+#define NextBufIdx(idx) \
+ (((idx) == XLogCtl->XLogCacheBlck) ? 0 : ((idx) + 1))
+
+/*
+ * XLogRecPtrToBufIdx returns the index of the WAL buffer that holds, or
+ * would hold if it was in cache, the page containing 'recptr'.
+ */
+#define XLogRecPtrToBufIdx(recptr) \
+ (((recptr) / XLOG_BLCKSZ) % (XLogCtl->XLogCacheBlck + 1))
+
+/*
+ * These are the number of bytes in a WAL page usable for WAL data.
+ */
+#define UsableBytesInPage (XLOG_BLCKSZ - SizeOfXLogShortPHD)
+
+/*
+ * Convert values of GUCs measured in megabytes to equiv. segment count.
+ * Rounds down.
+ */
+#define ConvertToXSegs(x, segsize) XLogMBVarToSegs((x), (segsize))
+
+/* The number of bytes in a WAL segment usable for WAL data. */
+static int UsableBytesInSegment;
+
+/*
+ * Private, possibly out-of-date copy of shared LogwrtResult.
+ * See discussion above.
+ */
+static XLogwrtResult LogwrtResult = {0, 0};
+
+/*
+ * openLogFile is -1 or a kernel FD for an open log file segment.
+ * openLogSegNo identifies the segment, and openLogTLI the corresponding TLI.
+ * These variables are only used to write the XLOG, and so will normally refer
+ * to the active segment.
+ *
+ * Note: call Reserve/ReleaseExternalFD to track consumption of this FD.
+ */
+static int openLogFile = -1;
+static XLogSegNo openLogSegNo = 0;
+static TimeLineID openLogTLI = 0;
+
+/*
+ * Local copies of equivalent fields in the control file. When running
+ * crash recovery, LocalMinRecoveryPoint is set to InvalidXLogRecPtr as we
+ * expect to replay all the WAL available, and updateMinRecoveryPoint is
+ * switched to false to prevent any updates while replaying records.
+ * Those values are kept consistent as long as crash recovery runs.
+ */
+static XLogRecPtr LocalMinRecoveryPoint;
+static TimeLineID LocalMinRecoveryPointTLI;
+static bool updateMinRecoveryPoint = true;
+
+/* For WALInsertLockAcquire/Release functions */
+static int MyLockNo = 0;
+static bool holdingAllLocks = false;
+
+#ifdef WAL_DEBUG
+static MemoryContext walDebugCxt = NULL;
+#endif
+
+static void CleanupAfterArchiveRecovery(TimeLineID EndOfLogTLI,
+ XLogRecPtr EndOfLog,
+ TimeLineID newTLI);
+static void CheckRequiredParameterValues(void);
+static void XLogReportParameters(void);
+static int LocalSetXLogInsertAllowed(void);
+static void CreateEndOfRecoveryRecord(void);
+static XLogRecPtr CreateOverwriteContrecordRecord(XLogRecPtr aborted_lsn,
+ XLogRecPtr missingContrecPtr,
+ TimeLineID newTLI);
+static void CheckPointGuts(XLogRecPtr checkPointRedo, int flags);
+static void KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo);
+static XLogRecPtr XLogGetReplicationSlotMinimumLSN(void);
+
+static void AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli,
+ bool opportunistic);
+static void XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible);
+static bool InstallXLogFileSegment(XLogSegNo *segno, char *tmppath,
+ bool find_free, XLogSegNo max_segno,
+ TimeLineID tli);
+static void XLogFileClose(void);
+static void PreallocXlogFiles(XLogRecPtr endptr, TimeLineID tli);
+static void RemoveTempXlogFiles(void);
+static void RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr lastredoptr,
+ XLogRecPtr endptr, TimeLineID insertTLI);
+static void RemoveXlogFile(const char *segname, XLogSegNo recycleSegNo,
+ XLogSegNo *endlogSegNo, TimeLineID insertTLI);
+static void UpdateLastRemovedPtr(char *filename);
+static void ValidateXLOGDirectoryStructure(void);
+static void CleanupBackupHistory(void);
+static void UpdateMinRecoveryPoint(XLogRecPtr lsn, bool force);
+static bool PerformRecoveryXLogAction(void);
+static void InitControlFile(uint64 sysidentifier);
+static void WriteControlFile(void);
+static void ReadControlFile(void);
+static void UpdateControlFile(void);
+static char *str_time(pg_time_t tnow);
+
+static void pg_backup_start_callback(int code, Datum arg);
+
+static int get_sync_bit(int method);
+
+static void CopyXLogRecordToWAL(int write_len, bool isLogSwitch,
+ XLogRecData *rdata,
+ XLogRecPtr StartPos, XLogRecPtr EndPos,
+ TimeLineID tli);
+static void ReserveXLogInsertLocation(int size, XLogRecPtr *StartPos,
+ XLogRecPtr *EndPos, XLogRecPtr *PrevPtr);
+static bool ReserveXLogSwitch(XLogRecPtr *StartPos, XLogRecPtr *EndPos,
+ XLogRecPtr *PrevPtr);
+static XLogRecPtr WaitXLogInsertionsToFinish(XLogRecPtr upto);
+static char *GetXLogBuffer(XLogRecPtr ptr, TimeLineID tli);
+static XLogRecPtr XLogBytePosToRecPtr(uint64 bytepos);
+static XLogRecPtr XLogBytePosToEndRecPtr(uint64 bytepos);
+static uint64 XLogRecPtrToBytePos(XLogRecPtr ptr);
+
+static void WALInsertLockAcquire(void);
+static void WALInsertLockAcquireExclusive(void);
+static void WALInsertLockRelease(void);
+static void WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt);
+
+/*
+ * Insert an XLOG record represented by an already-constructed chain of data
+ * chunks. This is a low-level routine; to construct the WAL record header
+ * and data, use the higher-level routines in xloginsert.c.
+ *
+ * If 'fpw_lsn' is valid, it is the oldest LSN among the pages that this
+ * WAL record applies to, that were not included in the record as full page
+ * images. If fpw_lsn <= RedoRecPtr, the function does not perform the
+ * insertion and returns InvalidXLogRecPtr. The caller can then recalculate
+ * which pages need a full-page image, and retry. If fpw_lsn is invalid, the
+ * record is always inserted.
+ *
+ * 'flags' gives more in-depth control on the record being inserted. See
+ * XLogSetRecordFlags() for details.
+ *
+ * 'topxid_included' tells whether the top-transaction id is logged along with
+ * current subtransaction. See XLogRecordAssemble().
+ *
+ * The first XLogRecData in the chain must be for the record header, and its
+ * data must be MAXALIGNed. XLogInsertRecord fills in the xl_prev and
+ * xl_crc fields in the header, the rest of the header must already be filled
+ * by the caller.
+ *
+ * Returns XLOG pointer to end of record (beginning of next record).
+ * This can be used as LSN for data pages affected by the logged action.
+ * (LSN is the XLOG point up to which the XLOG must be flushed to disk
+ * before the data page can be written out. This implements the basic
+ * WAL rule "write the log before the data".)
+ */
+XLogRecPtr
+XLogInsertRecord(XLogRecData *rdata,
+ XLogRecPtr fpw_lsn,
+ uint8 flags,
+ int num_fpi,
+ bool topxid_included)
+{
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ pg_crc32c rdata_crc;
+ bool inserted;
+ XLogRecord *rechdr = (XLogRecord *) rdata->data;
+ uint8 info = rechdr->xl_info & ~XLR_INFO_MASK;
+ bool isLogSwitch = (rechdr->xl_rmid == RM_XLOG_ID &&
+ info == XLOG_SWITCH);
+ XLogRecPtr StartPos;
+ XLogRecPtr EndPos;
+ bool prevDoPageWrites = doPageWrites;
+ TimeLineID insertTLI;
+
+ /* we assume that all of the record header is in the first chunk */
+ Assert(rdata->len >= SizeOfXLogRecord);
+
+ /* cross-check on whether we should be here or not */
+ if (!XLogInsertAllowed())
+ elog(ERROR, "cannot make new WAL entries during recovery");
+
+ /*
+ * Given that we're not in recovery, InsertTimeLineID is set and can't
+ * change, so we can read it without a lock.
+ */
+ insertTLI = XLogCtl->InsertTimeLineID;
+
+ /*----------
+ *
+ * We have now done all the preparatory work we can without holding a
+ * lock or modifying shared state. From here on, inserting the new WAL
+ * record to the shared WAL buffer cache is a two-step process:
+ *
+ * 1. Reserve the right amount of space from the WAL. The current head of
+ * reserved space is kept in Insert->CurrBytePos, and is protected by
+ * insertpos_lck.
+ *
+ * 2. Copy the record to the reserved WAL space. This involves finding the
+ * correct WAL buffer containing the reserved space, and copying the
+ * record in place. This can be done concurrently in multiple processes.
+ *
+ * To keep track of which insertions are still in-progress, each concurrent
+ * inserter acquires an insertion lock. In addition to just indicating that
+ * an insertion is in progress, the lock tells others how far the inserter
+ * has progressed. There is a small fixed number of insertion locks,
+ * determined by NUM_XLOGINSERT_LOCKS. When an inserter crosses a page
+ * boundary, it updates the value stored in the lock to the how far it has
+ * inserted, to allow the previous buffer to be flushed.
+ *
+ * Holding onto an insertion lock also protects RedoRecPtr and
+ * fullPageWrites from changing until the insertion is finished.
+ *
+ * Step 2 can usually be done completely in parallel. If the required WAL
+ * page is not initialized yet, you have to grab WALBufMappingLock to
+ * initialize it, but the WAL writer tries to do that ahead of insertions
+ * to avoid that from happening in the critical path.
+ *
+ *----------
+ */
+ START_CRIT_SECTION();
+ if (isLogSwitch)
+ WALInsertLockAcquireExclusive();
+ else
+ WALInsertLockAcquire();
+
+ /*
+ * Check to see if my copy of RedoRecPtr is out of date. If so, may have
+ * to go back and have the caller recompute everything. This can only
+ * happen just after a checkpoint, so it's better to be slow in this case
+ * and fast otherwise.
+ *
+ * Also check to see if fullPageWrites or forcePageWrites was just turned
+ * on; if we weren't already doing full-page writes then go back and
+ * recompute.
+ *
+ * If we aren't doing full-page writes then RedoRecPtr doesn't actually
+ * affect the contents of the XLOG record, so we'll update our local copy
+ * but not force a recomputation. (If doPageWrites was just turned off,
+ * we could recompute the record without full pages, but we choose not to
+ * bother.)
+ */
+ if (RedoRecPtr != Insert->RedoRecPtr)
+ {
+ Assert(RedoRecPtr < Insert->RedoRecPtr);
+ RedoRecPtr = Insert->RedoRecPtr;
+ }
+ doPageWrites = (Insert->fullPageWrites || Insert->forcePageWrites);
+
+ if (doPageWrites &&
+ (!prevDoPageWrites ||
+ (fpw_lsn != InvalidXLogRecPtr && fpw_lsn <= RedoRecPtr)))
+ {
+ /*
+ * Oops, some buffer now needs to be backed up that the caller didn't
+ * back up. Start over.
+ */
+ WALInsertLockRelease();
+ END_CRIT_SECTION();
+ return InvalidXLogRecPtr;
+ }
+
+ /*
+ * Reserve space for the record in the WAL. This also sets the xl_prev
+ * pointer.
+ */
+ if (isLogSwitch)
+ inserted = ReserveXLogSwitch(&StartPos, &EndPos, &rechdr->xl_prev);
+ else
+ {
+ ReserveXLogInsertLocation(rechdr->xl_tot_len, &StartPos, &EndPos,
+ &rechdr->xl_prev);
+ inserted = true;
+ }
+
+ if (inserted)
+ {
+ /*
+ * Now that xl_prev has been filled in, calculate CRC of the record
+ * header.
+ */
+ rdata_crc = rechdr->xl_crc;
+ COMP_CRC32C(rdata_crc, rechdr, offsetof(XLogRecord, xl_crc));
+ FIN_CRC32C(rdata_crc);
+ rechdr->xl_crc = rdata_crc;
+
+ /*
+ * All the record data, including the header, is now ready to be
+ * inserted. Copy the record in the space reserved.
+ */
+ CopyXLogRecordToWAL(rechdr->xl_tot_len, isLogSwitch, rdata,
+ StartPos, EndPos, insertTLI);
+
+ /*
+ * Unless record is flagged as not important, update LSN of last
+ * important record in the current slot. When holding all locks, just
+ * update the first one.
+ */
+ if ((flags & XLOG_MARK_UNIMPORTANT) == 0)
+ {
+ int lockno = holdingAllLocks ? 0 : MyLockNo;
+
+ WALInsertLocks[lockno].l.lastImportantAt = StartPos;
+ }
+ }
+ else
+ {
+ /*
+ * This was an xlog-switch record, but the current insert location was
+ * already exactly at the beginning of a segment, so there was no need
+ * to do anything.
+ */
+ }
+
+ /*
+ * Done! Let others know that we're finished.
+ */
+ WALInsertLockRelease();
+
+ END_CRIT_SECTION();
+
+ MarkCurrentTransactionIdLoggedIfAny();
+
+ /*
+ * Mark top transaction id is logged (if needed) so that we should not try
+ * to log it again with the next WAL record in the current subtransaction.
+ */
+ if (topxid_included)
+ MarkSubxactTopXidLogged();
+
+ /*
+ * Update shared LogwrtRqst.Write, if we crossed page boundary.
+ */
+ if (StartPos / XLOG_BLCKSZ != EndPos / XLOG_BLCKSZ)
+ {
+ SpinLockAcquire(&XLogCtl->info_lck);
+ /* advance global request to include new block(s) */
+ if (XLogCtl->LogwrtRqst.Write < EndPos)
+ XLogCtl->LogwrtRqst.Write = EndPos;
+ /* update local result copy while I have the chance */
+ LogwrtResult = XLogCtl->LogwrtResult;
+ SpinLockRelease(&XLogCtl->info_lck);
+ }
+
+ /*
+ * If this was an XLOG_SWITCH record, flush the record and the empty
+ * padding space that fills the rest of the segment, and perform
+ * end-of-segment actions (eg, notifying archiver).
+ */
+ if (isLogSwitch)
+ {
+ TRACE_POSTGRESQL_WAL_SWITCH();
+ XLogFlush(EndPos);
+
+ /*
+ * Even though we reserved the rest of the segment for us, which is
+ * reflected in EndPos, we return a pointer to just the end of the
+ * xlog-switch record.
+ */
+ if (inserted)
+ {
+ EndPos = StartPos + SizeOfXLogRecord;
+ if (StartPos / XLOG_BLCKSZ != EndPos / XLOG_BLCKSZ)
+ {
+ uint64 offset = XLogSegmentOffset(EndPos, wal_segment_size);
+
+ if (offset == EndPos % XLOG_BLCKSZ)
+ EndPos += SizeOfXLogLongPHD;
+ else
+ EndPos += SizeOfXLogShortPHD;
+ }
+ }
+ }
+
+#ifdef WAL_DEBUG
+ if (XLOG_DEBUG)
+ {
+ static XLogReaderState *debug_reader = NULL;
+ XLogRecord *record;
+ DecodedXLogRecord *decoded;
+ StringInfoData buf;
+ StringInfoData recordBuf;
+ char *errormsg = NULL;
+ MemoryContext oldCxt;
+
+ oldCxt = MemoryContextSwitchTo(walDebugCxt);
+
+ initStringInfo(&buf);
+ appendStringInfo(&buf, "INSERT @ %X/%X: ", LSN_FORMAT_ARGS(EndPos));
+
+ /*
+ * We have to piece together the WAL record data from the XLogRecData
+ * entries, so that we can pass it to the rm_desc function as one
+ * contiguous chunk.
+ */
+ initStringInfo(&recordBuf);
+ for (; rdata != NULL; rdata = rdata->next)
+ appendBinaryStringInfo(&recordBuf, rdata->data, rdata->len);
+
+ /* We also need temporary space to decode the record. */
+ record = (XLogRecord *) recordBuf.data;
+ decoded = (DecodedXLogRecord *)
+ palloc(DecodeXLogRecordRequiredSpace(record->xl_tot_len));
+
+ if (!debug_reader)
+ debug_reader = XLogReaderAllocate(wal_segment_size, NULL,
+ XL_ROUTINE(), NULL);
+
+ if (!debug_reader)
+ {
+ appendStringInfoString(&buf, "error decoding record: out of memory while allocating a WAL reading processor");
+ }
+ else if (!DecodeXLogRecord(debug_reader,
+ decoded,
+ record,
+ EndPos,
+ &errormsg))
+ {
+ appendStringInfo(&buf, "error decoding record: %s",
+ errormsg ? errormsg : "no error message");
+ }
+ else
+ {
+ appendStringInfoString(&buf, " - ");
+
+ debug_reader->record = decoded;
+ xlog_outdesc(&buf, debug_reader);
+ debug_reader->record = NULL;
+ }
+ elog(LOG, "%s", buf.data);
+
+ pfree(decoded);
+ pfree(buf.data);
+ pfree(recordBuf.data);
+ MemoryContextSwitchTo(oldCxt);
+ }
+#endif
+
+ /*
+ * Update our global variables
+ */
+ ProcLastRecPtr = StartPos;
+ XactLastRecEnd = EndPos;
+
+ /* Report WAL traffic to the instrumentation. */
+ if (inserted)
+ {
+ pgWalUsage.wal_bytes += rechdr->xl_tot_len;
+ pgWalUsage.wal_records++;
+ pgWalUsage.wal_fpi += num_fpi;
+ }
+
+ return EndPos;
+}
+
+/*
+ * Reserves the right amount of space for a record of given size from the WAL.
+ * *StartPos is set to the beginning of the reserved section, *EndPos to
+ * its end+1. *PrevPtr is set to the beginning of the previous record; it is
+ * used to set the xl_prev of this record.
+ *
+ * This is the performance critical part of XLogInsert that must be serialized
+ * across backends. The rest can happen mostly in parallel. Try to keep this
+ * section as short as possible, insertpos_lck can be heavily contended on a
+ * busy system.
+ *
+ * NB: The space calculation here must match the code in CopyXLogRecordToWAL,
+ * where we actually copy the record to the reserved space.
+ */
+static void
+ReserveXLogInsertLocation(int size, XLogRecPtr *StartPos, XLogRecPtr *EndPos,
+ XLogRecPtr *PrevPtr)
+{
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ uint64 startbytepos;
+ uint64 endbytepos;
+ uint64 prevbytepos;
+
+ size = MAXALIGN(size);
+
+ /* All (non xlog-switch) records should contain data. */
+ Assert(size > SizeOfXLogRecord);
+
+ /*
+ * The duration the spinlock needs to be held is minimized by minimizing
+ * the calculations that have to be done while holding the lock. The
+ * current tip of reserved WAL is kept in CurrBytePos, as a byte position
+ * that only counts "usable" bytes in WAL, that is, it excludes all WAL
+ * page headers. The mapping between "usable" byte positions and physical
+ * positions (XLogRecPtrs) can be done outside the locked region, and
+ * because the usable byte position doesn't include any headers, reserving
+ * X bytes from WAL is almost as simple as "CurrBytePos += X".
+ */
+ SpinLockAcquire(&Insert->insertpos_lck);
+
+ startbytepos = Insert->CurrBytePos;
+ endbytepos = startbytepos + size;
+ prevbytepos = Insert->PrevBytePos;
+ Insert->CurrBytePos = endbytepos;
+ Insert->PrevBytePos = startbytepos;
+
+ SpinLockRelease(&Insert->insertpos_lck);
+
+ *StartPos = XLogBytePosToRecPtr(startbytepos);
+ *EndPos = XLogBytePosToEndRecPtr(endbytepos);
+ *PrevPtr = XLogBytePosToRecPtr(prevbytepos);
+
+ /*
+ * Check that the conversions between "usable byte positions" and
+ * XLogRecPtrs work consistently in both directions.
+ */
+ Assert(XLogRecPtrToBytePos(*StartPos) == startbytepos);
+ Assert(XLogRecPtrToBytePos(*EndPos) == endbytepos);
+ Assert(XLogRecPtrToBytePos(*PrevPtr) == prevbytepos);
+}
+
+/*
+ * Like ReserveXLogInsertLocation(), but for an xlog-switch record.
+ *
+ * A log-switch record is handled slightly differently. The rest of the
+ * segment will be reserved for this insertion, as indicated by the returned
+ * *EndPos value. However, if we are already at the beginning of the current
+ * segment, *StartPos and *EndPos are set to the current location without
+ * reserving any space, and the function returns false.
+*/
+static bool
+ReserveXLogSwitch(XLogRecPtr *StartPos, XLogRecPtr *EndPos, XLogRecPtr *PrevPtr)
+{
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ uint64 startbytepos;
+ uint64 endbytepos;
+ uint64 prevbytepos;
+ uint32 size = MAXALIGN(SizeOfXLogRecord);
+ XLogRecPtr ptr;
+ uint32 segleft;
+
+ /*
+ * These calculations are a bit heavy-weight to be done while holding a
+ * spinlock, but since we're holding all the WAL insertion locks, there
+ * are no other inserters competing for it. GetXLogInsertRecPtr() does
+ * compete for it, but that's not called very frequently.
+ */
+ SpinLockAcquire(&Insert->insertpos_lck);
+
+ startbytepos = Insert->CurrBytePos;
+
+ ptr = XLogBytePosToEndRecPtr(startbytepos);
+ if (XLogSegmentOffset(ptr, wal_segment_size) == 0)
+ {
+ SpinLockRelease(&Insert->insertpos_lck);
+ *EndPos = *StartPos = ptr;
+ return false;
+ }
+
+ endbytepos = startbytepos + size;
+ prevbytepos = Insert->PrevBytePos;
+
+ *StartPos = XLogBytePosToRecPtr(startbytepos);
+ *EndPos = XLogBytePosToEndRecPtr(endbytepos);
+
+ segleft = wal_segment_size - XLogSegmentOffset(*EndPos, wal_segment_size);
+ if (segleft != wal_segment_size)
+ {
+ /* consume the rest of the segment */
+ *EndPos += segleft;
+ endbytepos = XLogRecPtrToBytePos(*EndPos);
+ }
+ Insert->CurrBytePos = endbytepos;
+ Insert->PrevBytePos = startbytepos;
+
+ SpinLockRelease(&Insert->insertpos_lck);
+
+ *PrevPtr = XLogBytePosToRecPtr(prevbytepos);
+
+ Assert(XLogSegmentOffset(*EndPos, wal_segment_size) == 0);
+ Assert(XLogRecPtrToBytePos(*EndPos) == endbytepos);
+ Assert(XLogRecPtrToBytePos(*StartPos) == startbytepos);
+ Assert(XLogRecPtrToBytePos(*PrevPtr) == prevbytepos);
+
+ return true;
+}
+
+/*
+ * Subroutine of XLogInsertRecord. Copies a WAL record to an already-reserved
+ * area in the WAL.
+ */
+static void
+CopyXLogRecordToWAL(int write_len, bool isLogSwitch, XLogRecData *rdata,
+ XLogRecPtr StartPos, XLogRecPtr EndPos, TimeLineID tli)
+{
+ char *currpos;
+ int freespace;
+ int written;
+ XLogRecPtr CurrPos;
+ XLogPageHeader pagehdr;
+
+ /*
+ * Get a pointer to the right place in the right WAL buffer to start
+ * inserting to.
+ */
+ CurrPos = StartPos;
+ currpos = GetXLogBuffer(CurrPos, tli);
+ freespace = INSERT_FREESPACE(CurrPos);
+
+ /*
+ * there should be enough space for at least the first field (xl_tot_len)
+ * on this page.
+ */
+ Assert(freespace >= sizeof(uint32));
+
+ /* Copy record data */
+ written = 0;
+ while (rdata != NULL)
+ {
+ char *rdata_data = rdata->data;
+ int rdata_len = rdata->len;
+
+ while (rdata_len > freespace)
+ {
+ /*
+ * Write what fits on this page, and continue on the next page.
+ */
+ Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD || freespace == 0);
+ memcpy(currpos, rdata_data, freespace);
+ rdata_data += freespace;
+ rdata_len -= freespace;
+ written += freespace;
+ CurrPos += freespace;
+
+ /*
+ * Get pointer to beginning of next page, and set the xlp_rem_len
+ * in the page header. Set XLP_FIRST_IS_CONTRECORD.
+ *
+ * It's safe to set the contrecord flag and xlp_rem_len without a
+ * lock on the page. All the other flags were already set when the
+ * page was initialized, in AdvanceXLInsertBuffer, and we're the
+ * only backend that needs to set the contrecord flag.
+ */
+ currpos = GetXLogBuffer(CurrPos, tli);
+ pagehdr = (XLogPageHeader) currpos;
+ pagehdr->xlp_rem_len = write_len - written;
+ pagehdr->xlp_info |= XLP_FIRST_IS_CONTRECORD;
+
+ /* skip over the page header */
+ if (XLogSegmentOffset(CurrPos, wal_segment_size) == 0)
+ {
+ CurrPos += SizeOfXLogLongPHD;
+ currpos += SizeOfXLogLongPHD;
+ }
+ else
+ {
+ CurrPos += SizeOfXLogShortPHD;
+ currpos += SizeOfXLogShortPHD;
+ }
+ freespace = INSERT_FREESPACE(CurrPos);
+ }
+
+ Assert(CurrPos % XLOG_BLCKSZ >= SizeOfXLogShortPHD || rdata_len == 0);
+ memcpy(currpos, rdata_data, rdata_len);
+ currpos += rdata_len;
+ CurrPos += rdata_len;
+ freespace -= rdata_len;
+ written += rdata_len;
+
+ rdata = rdata->next;
+ }
+ Assert(written == write_len);
+
+ /*
+ * If this was an xlog-switch, it's not enough to write the switch record,
+ * we also have to consume all the remaining space in the WAL segment. We
+ * have already reserved that space, but we need to actually fill it.
+ */
+ if (isLogSwitch && XLogSegmentOffset(CurrPos, wal_segment_size) != 0)
+ {
+ /* An xlog-switch record doesn't contain any data besides the header */
+ Assert(write_len == SizeOfXLogRecord);
+
+ /* Assert that we did reserve the right amount of space */
+ Assert(XLogSegmentOffset(EndPos, wal_segment_size) == 0);
+
+ /* Use up all the remaining space on the current page */
+ CurrPos += freespace;
+
+ /*
+ * Cause all remaining pages in the segment to be flushed, leaving the
+ * XLog position where it should be, at the start of the next segment.
+ * We do this one page at a time, to make sure we don't deadlock
+ * against ourselves if wal_buffers < wal_segment_size.
+ */
+ while (CurrPos < EndPos)
+ {
+ /*
+ * The minimal action to flush the page would be to call
+ * WALInsertLockUpdateInsertingAt(CurrPos) followed by
+ * AdvanceXLInsertBuffer(...). The page would be left initialized
+ * mostly to zeros, except for the page header (always the short
+ * variant, as this is never a segment's first page).
+ *
+ * The large vistas of zeros are good for compressibility, but the
+ * headers interrupting them every XLOG_BLCKSZ (with values that
+ * differ from page to page) are not. The effect varies with
+ * compression tool, but bzip2 for instance compresses about an
+ * order of magnitude worse if those headers are left in place.
+ *
+ * Rather than complicating AdvanceXLInsertBuffer itself (which is
+ * called in heavily-loaded circumstances as well as this lightly-
+ * loaded one) with variant behavior, we just use GetXLogBuffer
+ * (which itself calls the two methods we need) to get the pointer
+ * and zero most of the page. Then we just zero the page header.
+ */
+ currpos = GetXLogBuffer(CurrPos, tli);
+ MemSet(currpos, 0, SizeOfXLogShortPHD);
+
+ CurrPos += XLOG_BLCKSZ;
+ }
+ }
+ else
+ {
+ /* Align the end position, so that the next record starts aligned */
+ CurrPos = MAXALIGN64(CurrPos);
+ }
+
+ if (CurrPos != EndPos)
+ elog(PANIC, "space reserved for WAL record does not match what was written");
+}
+
+/*
+ * Acquire a WAL insertion lock, for inserting to WAL.
+ */
+static void
+WALInsertLockAcquire(void)
+{
+ bool immed;
+
+ /*
+ * It doesn't matter which of the WAL insertion locks we acquire, so try
+ * the one we used last time. If the system isn't particularly busy, it's
+ * a good bet that it's still available, and it's good to have some
+ * affinity to a particular lock so that you don't unnecessarily bounce
+ * cache lines between processes when there's no contention.
+ *
+ * If this is the first time through in this backend, pick a lock
+ * (semi-)randomly. This allows the locks to be used evenly if you have a
+ * lot of very short connections.
+ */
+ static int lockToTry = -1;
+
+ if (lockToTry == -1)
+ lockToTry = MyProc->pgprocno % NUM_XLOGINSERT_LOCKS;
+ MyLockNo = lockToTry;
+
+ /*
+ * The insertingAt value is initially set to 0, as we don't know our
+ * insert location yet.
+ */
+ immed = LWLockAcquire(&WALInsertLocks[MyLockNo].l.lock, LW_EXCLUSIVE);
+ if (!immed)
+ {
+ /*
+ * If we couldn't get the lock immediately, try another lock next
+ * time. On a system with more insertion locks than concurrent
+ * inserters, this causes all the inserters to eventually migrate to a
+ * lock that no-one else is using. On a system with more inserters
+ * than locks, it still helps to distribute the inserters evenly
+ * across the locks.
+ */
+ lockToTry = (lockToTry + 1) % NUM_XLOGINSERT_LOCKS;
+ }
+}
+
+/*
+ * Acquire all WAL insertion locks, to prevent other backends from inserting
+ * to WAL.
+ */
+static void
+WALInsertLockAcquireExclusive(void)
+{
+ int i;
+
+ /*
+ * When holding all the locks, all but the last lock's insertingAt
+ * indicator is set to 0xFFFFFFFFFFFFFFFF, which is higher than any real
+ * XLogRecPtr value, to make sure that no-one blocks waiting on those.
+ */
+ for (i = 0; i < NUM_XLOGINSERT_LOCKS - 1; i++)
+ {
+ LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE);
+ LWLockUpdateVar(&WALInsertLocks[i].l.lock,
+ &WALInsertLocks[i].l.insertingAt,
+ PG_UINT64_MAX);
+ }
+ /* Variable value reset to 0 at release */
+ LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE);
+
+ holdingAllLocks = true;
+}
+
+/*
+ * Release our insertion lock (or locks, if we're holding them all).
+ *
+ * NB: Reset all variables to 0, so they cause LWLockWaitForVar to block the
+ * next time the lock is acquired.
+ */
+static void
+WALInsertLockRelease(void)
+{
+ if (holdingAllLocks)
+ {
+ int i;
+
+ for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++)
+ LWLockReleaseClearVar(&WALInsertLocks[i].l.lock,
+ &WALInsertLocks[i].l.insertingAt,
+ 0);
+
+ holdingAllLocks = false;
+ }
+ else
+ {
+ LWLockReleaseClearVar(&WALInsertLocks[MyLockNo].l.lock,
+ &WALInsertLocks[MyLockNo].l.insertingAt,
+ 0);
+ }
+}
+
+/*
+ * Update our insertingAt value, to let others know that we've finished
+ * inserting up to that point.
+ */
+static void
+WALInsertLockUpdateInsertingAt(XLogRecPtr insertingAt)
+{
+ if (holdingAllLocks)
+ {
+ /*
+ * We use the last lock to mark our actual position, see comments in
+ * WALInsertLockAcquireExclusive.
+ */
+ LWLockUpdateVar(&WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.lock,
+ &WALInsertLocks[NUM_XLOGINSERT_LOCKS - 1].l.insertingAt,
+ insertingAt);
+ }
+ else
+ LWLockUpdateVar(&WALInsertLocks[MyLockNo].l.lock,
+ &WALInsertLocks[MyLockNo].l.insertingAt,
+ insertingAt);
+}
+
+/*
+ * Wait for any WAL insertions < upto to finish.
+ *
+ * Returns the location of the oldest insertion that is still in-progress.
+ * Any WAL prior to that point has been fully copied into WAL buffers, and
+ * can be flushed out to disk. Because this waits for any insertions older
+ * than 'upto' to finish, the return value is always >= 'upto'.
+ *
+ * Note: When you are about to write out WAL, you must call this function
+ * *before* acquiring WALWriteLock, to avoid deadlocks. This function might
+ * need to wait for an insertion to finish (or at least advance to next
+ * uninitialized page), and the inserter might need to evict an old WAL buffer
+ * to make room for a new one, which in turn requires WALWriteLock.
+ */
+static XLogRecPtr
+WaitXLogInsertionsToFinish(XLogRecPtr upto)
+{
+ uint64 bytepos;
+ XLogRecPtr reservedUpto;
+ XLogRecPtr finishedUpto;
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ int i;
+
+ if (MyProc == NULL)
+ elog(PANIC, "cannot wait without a PGPROC structure");
+
+ /* Read the current insert position */
+ SpinLockAcquire(&Insert->insertpos_lck);
+ bytepos = Insert->CurrBytePos;
+ SpinLockRelease(&Insert->insertpos_lck);
+ reservedUpto = XLogBytePosToEndRecPtr(bytepos);
+
+ /*
+ * No-one should request to flush a piece of WAL that hasn't even been
+ * reserved yet. However, it can happen if there is a block with a bogus
+ * LSN on disk, for example. XLogFlush checks for that situation and
+ * complains, but only after the flush. Here we just assume that to mean
+ * that all WAL that has been reserved needs to be finished. In this
+ * corner-case, the return value can be smaller than 'upto' argument.
+ */
+ if (upto > reservedUpto)
+ {
+ ereport(LOG,
+ (errmsg("request to flush past end of generated WAL; request %X/%X, current position %X/%X",
+ LSN_FORMAT_ARGS(upto), LSN_FORMAT_ARGS(reservedUpto))));
+ upto = reservedUpto;
+ }
+
+ /*
+ * Loop through all the locks, sleeping on any in-progress insert older
+ * than 'upto'.
+ *
+ * finishedUpto is our return value, indicating the point upto which all
+ * the WAL insertions have been finished. Initialize it to the head of
+ * reserved WAL, and as we iterate through the insertion locks, back it
+ * out for any insertion that's still in progress.
+ */
+ finishedUpto = reservedUpto;
+ for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++)
+ {
+ XLogRecPtr insertingat = InvalidXLogRecPtr;
+
+ do
+ {
+ /*
+ * See if this insertion is in progress. LWLockWaitForVar will
+ * wait for the lock to be released, or for the 'value' to be set
+ * by a LWLockUpdateVar call. When a lock is initially acquired,
+ * its value is 0 (InvalidXLogRecPtr), which means that we don't
+ * know where it's inserting yet. We will have to wait for it. If
+ * it's a small insertion, the record will most likely fit on the
+ * same page and the inserter will release the lock without ever
+ * calling LWLockUpdateVar. But if it has to sleep, it will
+ * advertise the insertion point with LWLockUpdateVar before
+ * sleeping.
+ */
+ if (LWLockWaitForVar(&WALInsertLocks[i].l.lock,
+ &WALInsertLocks[i].l.insertingAt,
+ insertingat, &insertingat))
+ {
+ /* the lock was free, so no insertion in progress */
+ insertingat = InvalidXLogRecPtr;
+ break;
+ }
+
+ /*
+ * This insertion is still in progress. Have to wait, unless the
+ * inserter has proceeded past 'upto'.
+ */
+ } while (insertingat < upto);
+
+ if (insertingat != InvalidXLogRecPtr && insertingat < finishedUpto)
+ finishedUpto = insertingat;
+ }
+ return finishedUpto;
+}
+
+/*
+ * Get a pointer to the right location in the WAL buffer containing the
+ * given XLogRecPtr.
+ *
+ * If the page is not initialized yet, it is initialized. That might require
+ * evicting an old dirty buffer from the buffer cache, which means I/O.
+ *
+ * The caller must ensure that the page containing the requested location
+ * isn't evicted yet, and won't be evicted. The way to ensure that is to
+ * hold onto a WAL insertion lock with the insertingAt position set to
+ * something <= ptr. GetXLogBuffer() will update insertingAt if it needs
+ * to evict an old page from the buffer. (This means that once you call
+ * GetXLogBuffer() with a given 'ptr', you must not access anything before
+ * that point anymore, and must not call GetXLogBuffer() with an older 'ptr'
+ * later, because older buffers might be recycled already)
+ */
+static char *
+GetXLogBuffer(XLogRecPtr ptr, TimeLineID tli)
+{
+ int idx;
+ XLogRecPtr endptr;
+ static uint64 cachedPage = 0;
+ static char *cachedPos = NULL;
+ XLogRecPtr expectedEndPtr;
+
+ /*
+ * Fast path for the common case that we need to access again the same
+ * page as last time.
+ */
+ if (ptr / XLOG_BLCKSZ == cachedPage)
+ {
+ Assert(((XLogPageHeader) cachedPos)->xlp_magic == XLOG_PAGE_MAGIC);
+ Assert(((XLogPageHeader) cachedPos)->xlp_pageaddr == ptr - (ptr % XLOG_BLCKSZ));
+ return cachedPos + ptr % XLOG_BLCKSZ;
+ }
+
+ /*
+ * The XLog buffer cache is organized so that a page is always loaded to a
+ * particular buffer. That way we can easily calculate the buffer a given
+ * page must be loaded into, from the XLogRecPtr alone.
+ */
+ idx = XLogRecPtrToBufIdx(ptr);
+
+ /*
+ * See what page is loaded in the buffer at the moment. It could be the
+ * page we're looking for, or something older. It can't be anything newer
+ * - that would imply the page we're looking for has already been written
+ * out to disk and evicted, and the caller is responsible for making sure
+ * that doesn't happen.
+ *
+ * However, we don't hold a lock while we read the value. If someone has
+ * just initialized the page, it's possible that we get a "torn read" of
+ * the XLogRecPtr if 64-bit fetches are not atomic on this platform. In
+ * that case we will see a bogus value. That's ok, we'll grab the mapping
+ * lock (in AdvanceXLInsertBuffer) and retry if we see anything else than
+ * the page we're looking for. But it means that when we do this unlocked
+ * read, we might see a value that appears to be ahead of the page we're
+ * looking for. Don't PANIC on that, until we've verified the value while
+ * holding the lock.
+ */
+ expectedEndPtr = ptr;
+ expectedEndPtr += XLOG_BLCKSZ - ptr % XLOG_BLCKSZ;
+
+ endptr = XLogCtl->xlblocks[idx];
+ if (expectedEndPtr != endptr)
+ {
+ XLogRecPtr initializedUpto;
+
+ /*
+ * Before calling AdvanceXLInsertBuffer(), which can block, let others
+ * know how far we're finished with inserting the record.
+ *
+ * NB: If 'ptr' points to just after the page header, advertise a
+ * position at the beginning of the page rather than 'ptr' itself. If
+ * there are no other insertions running, someone might try to flush
+ * up to our advertised location. If we advertised a position after
+ * the page header, someone might try to flush the page header, even
+ * though page might actually not be initialized yet. As the first
+ * inserter on the page, we are effectively responsible for making
+ * sure that it's initialized, before we let insertingAt to move past
+ * the page header.
+ */
+ if (ptr % XLOG_BLCKSZ == SizeOfXLogShortPHD &&
+ XLogSegmentOffset(ptr, wal_segment_size) > XLOG_BLCKSZ)
+ initializedUpto = ptr - SizeOfXLogShortPHD;
+ else if (ptr % XLOG_BLCKSZ == SizeOfXLogLongPHD &&
+ XLogSegmentOffset(ptr, wal_segment_size) < XLOG_BLCKSZ)
+ initializedUpto = ptr - SizeOfXLogLongPHD;
+ else
+ initializedUpto = ptr;
+
+ WALInsertLockUpdateInsertingAt(initializedUpto);
+
+ AdvanceXLInsertBuffer(ptr, tli, false);
+ endptr = XLogCtl->xlblocks[idx];
+
+ if (expectedEndPtr != endptr)
+ elog(PANIC, "could not find WAL buffer for %X/%X",
+ LSN_FORMAT_ARGS(ptr));
+ }
+ else
+ {
+ /*
+ * Make sure the initialization of the page is visible to us, and
+ * won't arrive later to overwrite the WAL data we write on the page.
+ */
+ pg_memory_barrier();
+ }
+
+ /*
+ * Found the buffer holding this page. Return a pointer to the right
+ * offset within the page.
+ */
+ cachedPage = ptr / XLOG_BLCKSZ;
+ cachedPos = XLogCtl->pages + idx * (Size) XLOG_BLCKSZ;
+
+ Assert(((XLogPageHeader) cachedPos)->xlp_magic == XLOG_PAGE_MAGIC);
+ Assert(((XLogPageHeader) cachedPos)->xlp_pageaddr == ptr - (ptr % XLOG_BLCKSZ));
+
+ return cachedPos + ptr % XLOG_BLCKSZ;
+}
+
+/*
+ * Converts a "usable byte position" to XLogRecPtr. A usable byte position
+ * is the position starting from the beginning of WAL, excluding all WAL
+ * page headers.
+ */
+static XLogRecPtr
+XLogBytePosToRecPtr(uint64 bytepos)
+{
+ uint64 fullsegs;
+ uint64 fullpages;
+ uint64 bytesleft;
+ uint32 seg_offset;
+ XLogRecPtr result;
+
+ fullsegs = bytepos / UsableBytesInSegment;
+ bytesleft = bytepos % UsableBytesInSegment;
+
+ if (bytesleft < XLOG_BLCKSZ - SizeOfXLogLongPHD)
+ {
+ /* fits on first page of segment */
+ seg_offset = bytesleft + SizeOfXLogLongPHD;
+ }
+ else
+ {
+ /* account for the first page on segment with long header */
+ seg_offset = XLOG_BLCKSZ;
+ bytesleft -= XLOG_BLCKSZ - SizeOfXLogLongPHD;
+
+ fullpages = bytesleft / UsableBytesInPage;
+ bytesleft = bytesleft % UsableBytesInPage;
+
+ seg_offset += fullpages * XLOG_BLCKSZ + bytesleft + SizeOfXLogShortPHD;
+ }
+
+ XLogSegNoOffsetToRecPtr(fullsegs, seg_offset, wal_segment_size, result);
+
+ return result;
+}
+
+/*
+ * Like XLogBytePosToRecPtr, but if the position is at a page boundary,
+ * returns a pointer to the beginning of the page (ie. before page header),
+ * not to where the first xlog record on that page would go to. This is used
+ * when converting a pointer to the end of a record.
+ */
+static XLogRecPtr
+XLogBytePosToEndRecPtr(uint64 bytepos)
+{
+ uint64 fullsegs;
+ uint64 fullpages;
+ uint64 bytesleft;
+ uint32 seg_offset;
+ XLogRecPtr result;
+
+ fullsegs = bytepos / UsableBytesInSegment;
+ bytesleft = bytepos % UsableBytesInSegment;
+
+ if (bytesleft < XLOG_BLCKSZ - SizeOfXLogLongPHD)
+ {
+ /* fits on first page of segment */
+ if (bytesleft == 0)
+ seg_offset = 0;
+ else
+ seg_offset = bytesleft + SizeOfXLogLongPHD;
+ }
+ else
+ {
+ /* account for the first page on segment with long header */
+ seg_offset = XLOG_BLCKSZ;
+ bytesleft -= XLOG_BLCKSZ - SizeOfXLogLongPHD;
+
+ fullpages = bytesleft / UsableBytesInPage;
+ bytesleft = bytesleft % UsableBytesInPage;
+
+ if (bytesleft == 0)
+ seg_offset += fullpages * XLOG_BLCKSZ + bytesleft;
+ else
+ seg_offset += fullpages * XLOG_BLCKSZ + bytesleft + SizeOfXLogShortPHD;
+ }
+
+ XLogSegNoOffsetToRecPtr(fullsegs, seg_offset, wal_segment_size, result);
+
+ return result;
+}
+
+/*
+ * Convert an XLogRecPtr to a "usable byte position".
+ */
+static uint64
+XLogRecPtrToBytePos(XLogRecPtr ptr)
+{
+ uint64 fullsegs;
+ uint32 fullpages;
+ uint32 offset;
+ uint64 result;
+
+ XLByteToSeg(ptr, fullsegs, wal_segment_size);
+
+ fullpages = (XLogSegmentOffset(ptr, wal_segment_size)) / XLOG_BLCKSZ;
+ offset = ptr % XLOG_BLCKSZ;
+
+ if (fullpages == 0)
+ {
+ result = fullsegs * UsableBytesInSegment;
+ if (offset > 0)
+ {
+ Assert(offset >= SizeOfXLogLongPHD);
+ result += offset - SizeOfXLogLongPHD;
+ }
+ }
+ else
+ {
+ result = fullsegs * UsableBytesInSegment +
+ (XLOG_BLCKSZ - SizeOfXLogLongPHD) + /* account for first page */
+ (fullpages - 1) * UsableBytesInPage; /* full pages */
+ if (offset > 0)
+ {
+ Assert(offset >= SizeOfXLogShortPHD);
+ result += offset - SizeOfXLogShortPHD;
+ }
+ }
+
+ return result;
+}
+
+/*
+ * Initialize XLOG buffers, writing out old buffers if they still contain
+ * unwritten data, upto the page containing 'upto'. Or if 'opportunistic' is
+ * true, initialize as many pages as we can without having to write out
+ * unwritten data. Any new pages are initialized to zeros, with pages headers
+ * initialized properly.
+ */
+static void
+AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli, bool opportunistic)
+{
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ int nextidx;
+ XLogRecPtr OldPageRqstPtr;
+ XLogwrtRqst WriteRqst;
+ XLogRecPtr NewPageEndPtr = InvalidXLogRecPtr;
+ XLogRecPtr NewPageBeginPtr;
+ XLogPageHeader NewPage;
+ int npages pg_attribute_unused() = 0;
+
+ LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE);
+
+ /*
+ * Now that we have the lock, check if someone initialized the page
+ * already.
+ */
+ while (upto >= XLogCtl->InitializedUpTo || opportunistic)
+ {
+ nextidx = XLogRecPtrToBufIdx(XLogCtl->InitializedUpTo);
+
+ /*
+ * Get ending-offset of the buffer page we need to replace (this may
+ * be zero if the buffer hasn't been used yet). Fall through if it's
+ * already written out.
+ */
+ OldPageRqstPtr = XLogCtl->xlblocks[nextidx];
+ if (LogwrtResult.Write < OldPageRqstPtr)
+ {
+ /*
+ * Nope, got work to do. If we just want to pre-initialize as much
+ * as we can without flushing, give up now.
+ */
+ if (opportunistic)
+ break;
+
+ /* Before waiting, get info_lck and update LogwrtResult */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ if (XLogCtl->LogwrtRqst.Write < OldPageRqstPtr)
+ XLogCtl->LogwrtRqst.Write = OldPageRqstPtr;
+ LogwrtResult = XLogCtl->LogwrtResult;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * Now that we have an up-to-date LogwrtResult value, see if we
+ * still need to write it or if someone else already did.
+ */
+ if (LogwrtResult.Write < OldPageRqstPtr)
+ {
+ /*
+ * Must acquire write lock. Release WALBufMappingLock first,
+ * to make sure that all insertions that we need to wait for
+ * can finish (up to this same position). Otherwise we risk
+ * deadlock.
+ */
+ LWLockRelease(WALBufMappingLock);
+
+ WaitXLogInsertionsToFinish(OldPageRqstPtr);
+
+ LWLockAcquire(WALWriteLock, LW_EXCLUSIVE);
+
+ LogwrtResult = XLogCtl->LogwrtResult;
+ if (LogwrtResult.Write >= OldPageRqstPtr)
+ {
+ /* OK, someone wrote it already */
+ LWLockRelease(WALWriteLock);
+ }
+ else
+ {
+ /* Have to write it ourselves */
+ TRACE_POSTGRESQL_WAL_BUFFER_WRITE_DIRTY_START();
+ WriteRqst.Write = OldPageRqstPtr;
+ WriteRqst.Flush = 0;
+ XLogWrite(WriteRqst, tli, false);
+ LWLockRelease(WALWriteLock);
+ PendingWalStats.wal_buffers_full++;
+ TRACE_POSTGRESQL_WAL_BUFFER_WRITE_DIRTY_DONE();
+ }
+ /* Re-acquire WALBufMappingLock and retry */
+ LWLockAcquire(WALBufMappingLock, LW_EXCLUSIVE);
+ continue;
+ }
+ }
+
+ /*
+ * Now the next buffer slot is free and we can set it up to be the
+ * next output page.
+ */
+ NewPageBeginPtr = XLogCtl->InitializedUpTo;
+ NewPageEndPtr = NewPageBeginPtr + XLOG_BLCKSZ;
+
+ Assert(XLogRecPtrToBufIdx(NewPageBeginPtr) == nextidx);
+
+ NewPage = (XLogPageHeader) (XLogCtl->pages + nextidx * (Size) XLOG_BLCKSZ);
+
+ /*
+ * Be sure to re-zero the buffer so that bytes beyond what we've
+ * written will look like zeroes and not valid XLOG records...
+ */
+ MemSet((char *) NewPage, 0, XLOG_BLCKSZ);
+
+ /*
+ * Fill the new page's header
+ */
+ NewPage->xlp_magic = XLOG_PAGE_MAGIC;
+
+ /* NewPage->xlp_info = 0; */ /* done by memset */
+ NewPage->xlp_tli = tli;
+ NewPage->xlp_pageaddr = NewPageBeginPtr;
+
+ /* NewPage->xlp_rem_len = 0; */ /* done by memset */
+
+ /*
+ * If online backup is not in progress, mark the header to indicate
+ * that WAL records beginning in this page have removable backup
+ * blocks. This allows the WAL archiver to know whether it is safe to
+ * compress archived WAL data by transforming full-block records into
+ * the non-full-block format. It is sufficient to record this at the
+ * page level because we force a page switch (in fact a segment
+ * switch) when starting a backup, so the flag will be off before any
+ * records can be written during the backup. At the end of a backup,
+ * the last page will be marked as all unsafe when perhaps only part
+ * is unsafe, but at worst the archiver would miss the opportunity to
+ * compress a few records.
+ */
+ if (!Insert->forcePageWrites)
+ NewPage->xlp_info |= XLP_BKP_REMOVABLE;
+
+ /*
+ * If first page of an XLOG segment file, make it a long header.
+ */
+ if ((XLogSegmentOffset(NewPage->xlp_pageaddr, wal_segment_size)) == 0)
+ {
+ XLogLongPageHeader NewLongPage = (XLogLongPageHeader) NewPage;
+
+ NewLongPage->xlp_sysid = ControlFile->system_identifier;
+ NewLongPage->xlp_seg_size = wal_segment_size;
+ NewLongPage->xlp_xlog_blcksz = XLOG_BLCKSZ;
+ NewPage->xlp_info |= XLP_LONG_HEADER;
+ }
+
+ /*
+ * Make sure the initialization of the page becomes visible to others
+ * before the xlblocks update. GetXLogBuffer() reads xlblocks without
+ * holding a lock.
+ */
+ pg_write_barrier();
+
+ *((volatile XLogRecPtr *) &XLogCtl->xlblocks[nextidx]) = NewPageEndPtr;
+
+ XLogCtl->InitializedUpTo = NewPageEndPtr;
+
+ npages++;
+ }
+ LWLockRelease(WALBufMappingLock);
+
+#ifdef WAL_DEBUG
+ if (XLOG_DEBUG && npages > 0)
+ {
+ elog(DEBUG1, "initialized %d pages, up to %X/%X",
+ npages, LSN_FORMAT_ARGS(NewPageEndPtr));
+ }
+#endif
+}
+
+/*
+ * Calculate CheckPointSegments based on max_wal_size_mb and
+ * checkpoint_completion_target.
+ */
+static void
+CalculateCheckpointSegments(void)
+{
+ double target;
+
+ /*-------
+ * Calculate the distance at which to trigger a checkpoint, to avoid
+ * exceeding max_wal_size_mb. This is based on two assumptions:
+ *
+ * a) we keep WAL for only one checkpoint cycle (prior to PG11 we kept
+ * WAL for two checkpoint cycles to allow us to recover from the
+ * secondary checkpoint if the first checkpoint failed, though we
+ * only did this on the primary anyway, not on standby. Keeping just
+ * one checkpoint simplifies processing and reduces disk space in
+ * many smaller databases.)
+ * b) during checkpoint, we consume checkpoint_completion_target *
+ * number of segments consumed between checkpoints.
+ *-------
+ */
+ target = (double) ConvertToXSegs(max_wal_size_mb, wal_segment_size) /
+ (1.0 + CheckPointCompletionTarget);
+
+ /* round down */
+ CheckPointSegments = (int) target;
+
+ if (CheckPointSegments < 1)
+ CheckPointSegments = 1;
+}
+
+void
+assign_max_wal_size(int newval, void *extra)
+{
+ max_wal_size_mb = newval;
+ CalculateCheckpointSegments();
+}
+
+void
+assign_checkpoint_completion_target(double newval, void *extra)
+{
+ CheckPointCompletionTarget = newval;
+ CalculateCheckpointSegments();
+}
+
+/*
+ * At a checkpoint, how many WAL segments to recycle as preallocated future
+ * XLOG segments? Returns the highest segment that should be preallocated.
+ */
+static XLogSegNo
+XLOGfileslop(XLogRecPtr lastredoptr)
+{
+ XLogSegNo minSegNo;
+ XLogSegNo maxSegNo;
+ double distance;
+ XLogSegNo recycleSegNo;
+
+ /*
+ * Calculate the segment numbers that min_wal_size_mb and max_wal_size_mb
+ * correspond to. Always recycle enough segments to meet the minimum, and
+ * remove enough segments to stay below the maximum.
+ */
+ minSegNo = lastredoptr / wal_segment_size +
+ ConvertToXSegs(min_wal_size_mb, wal_segment_size) - 1;
+ maxSegNo = lastredoptr / wal_segment_size +
+ ConvertToXSegs(max_wal_size_mb, wal_segment_size) - 1;
+
+ /*
+ * Between those limits, recycle enough segments to get us through to the
+ * estimated end of next checkpoint.
+ *
+ * To estimate where the next checkpoint will finish, assume that the
+ * system runs steadily consuming CheckPointDistanceEstimate bytes between
+ * every checkpoint.
+ */
+ distance = (1.0 + CheckPointCompletionTarget) * CheckPointDistanceEstimate;
+ /* add 10% for good measure. */
+ distance *= 1.10;
+
+ recycleSegNo = (XLogSegNo) ceil(((double) lastredoptr + distance) /
+ wal_segment_size);
+
+ if (recycleSegNo < minSegNo)
+ recycleSegNo = minSegNo;
+ if (recycleSegNo > maxSegNo)
+ recycleSegNo = maxSegNo;
+
+ return recycleSegNo;
+}
+
+/*
+ * Check whether we've consumed enough xlog space that a checkpoint is needed.
+ *
+ * new_segno indicates a log file that has just been filled up (or read
+ * during recovery). We measure the distance from RedoRecPtr to new_segno
+ * and see if that exceeds CheckPointSegments.
+ *
+ * Note: it is caller's responsibility that RedoRecPtr is up-to-date.
+ */
+bool
+XLogCheckpointNeeded(XLogSegNo new_segno)
+{
+ XLogSegNo old_segno;
+
+ XLByteToSeg(RedoRecPtr, old_segno, wal_segment_size);
+
+ if (new_segno >= old_segno + (uint64) (CheckPointSegments - 1))
+ return true;
+ return false;
+}
+
+/*
+ * Write and/or fsync the log at least as far as WriteRqst indicates.
+ *
+ * If flexible == true, we don't have to write as far as WriteRqst, but
+ * may stop at any convenient boundary (such as a cache or logfile boundary).
+ * This option allows us to avoid uselessly issuing multiple writes when a
+ * single one would do.
+ *
+ * Must be called with WALWriteLock held. WaitXLogInsertionsToFinish(WriteRqst)
+ * must be called before grabbing the lock, to make sure the data is ready to
+ * write.
+ */
+static void
+XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible)
+{
+ bool ispartialpage;
+ bool last_iteration;
+ bool finishing_seg;
+ int curridx;
+ int npages;
+ int startidx;
+ uint32 startoffset;
+
+ /* We should always be inside a critical section here */
+ Assert(CritSectionCount > 0);
+
+ /*
+ * Update local LogwrtResult (caller probably did this already, but...)
+ */
+ LogwrtResult = XLogCtl->LogwrtResult;
+
+ /*
+ * Since successive pages in the xlog cache are consecutively allocated,
+ * we can usually gather multiple pages together and issue just one
+ * write() call. npages is the number of pages we have determined can be
+ * written together; startidx is the cache block index of the first one,
+ * and startoffset is the file offset at which it should go. The latter
+ * two variables are only valid when npages > 0, but we must initialize
+ * all of them to keep the compiler quiet.
+ */
+ npages = 0;
+ startidx = 0;
+ startoffset = 0;
+
+ /*
+ * Within the loop, curridx is the cache block index of the page to
+ * consider writing. Begin at the buffer containing the next unwritten
+ * page, or last partially written page.
+ */
+ curridx = XLogRecPtrToBufIdx(LogwrtResult.Write);
+
+ while (LogwrtResult.Write < WriteRqst.Write)
+ {
+ /*
+ * Make sure we're not ahead of the insert process. This could happen
+ * if we're passed a bogus WriteRqst.Write that is past the end of the
+ * last page that's been initialized by AdvanceXLInsertBuffer.
+ */
+ XLogRecPtr EndPtr = XLogCtl->xlblocks[curridx];
+
+ if (LogwrtResult.Write >= EndPtr)
+ elog(PANIC, "xlog write request %X/%X is past end of log %X/%X",
+ LSN_FORMAT_ARGS(LogwrtResult.Write),
+ LSN_FORMAT_ARGS(EndPtr));
+
+ /* Advance LogwrtResult.Write to end of current buffer page */
+ LogwrtResult.Write = EndPtr;
+ ispartialpage = WriteRqst.Write < LogwrtResult.Write;
+
+ if (!XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo,
+ wal_segment_size))
+ {
+ /*
+ * Switch to new logfile segment. We cannot have any pending
+ * pages here (since we dump what we have at segment end).
+ */
+ Assert(npages == 0);
+ if (openLogFile >= 0)
+ XLogFileClose();
+ XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo,
+ wal_segment_size);
+ openLogTLI = tli;
+
+ /* create/use new log file */
+ openLogFile = XLogFileInit(openLogSegNo, tli);
+ ReserveExternalFD();
+ }
+
+ /* Make sure we have the current logfile open */
+ if (openLogFile < 0)
+ {
+ XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo,
+ wal_segment_size);
+ openLogTLI = tli;
+ openLogFile = XLogFileOpen(openLogSegNo, tli);
+ ReserveExternalFD();
+ }
+
+ /* Add current page to the set of pending pages-to-dump */
+ if (npages == 0)
+ {
+ /* first of group */
+ startidx = curridx;
+ startoffset = XLogSegmentOffset(LogwrtResult.Write - XLOG_BLCKSZ,
+ wal_segment_size);
+ }
+ npages++;
+
+ /*
+ * Dump the set if this will be the last loop iteration, or if we are
+ * at the last page of the cache area (since the next page won't be
+ * contiguous in memory), or if we are at the end of the logfile
+ * segment.
+ */
+ last_iteration = WriteRqst.Write <= LogwrtResult.Write;
+
+ finishing_seg = !ispartialpage &&
+ (startoffset + npages * XLOG_BLCKSZ) >= wal_segment_size;
+
+ if (last_iteration ||
+ curridx == XLogCtl->XLogCacheBlck ||
+ finishing_seg)
+ {
+ char *from;
+ Size nbytes;
+ Size nleft;
+ int written;
+ instr_time start;
+
+ /* OK to write the page(s) */
+ from = XLogCtl->pages + startidx * (Size) XLOG_BLCKSZ;
+ nbytes = npages * (Size) XLOG_BLCKSZ;
+ nleft = nbytes;
+ do
+ {
+ errno = 0;
+
+ /* Measure I/O timing to write WAL data */
+ if (track_wal_io_timing)
+ INSTR_TIME_SET_CURRENT(start);
+
+ pgstat_report_wait_start(WAIT_EVENT_WAL_WRITE);
+ written = pg_pwrite(openLogFile, from, nleft, startoffset);
+ pgstat_report_wait_end();
+
+ /*
+ * Increment the I/O timing and the number of times WAL data
+ * were written out to disk.
+ */
+ if (track_wal_io_timing)
+ {
+ instr_time duration;
+
+ INSTR_TIME_SET_CURRENT(duration);
+ INSTR_TIME_SUBTRACT(duration, start);
+ PendingWalStats.wal_write_time += INSTR_TIME_GET_MICROSEC(duration);
+ }
+
+ PendingWalStats.wal_write++;
+
+ if (written <= 0)
+ {
+ char xlogfname[MAXFNAMELEN];
+ int save_errno;
+
+ if (errno == EINTR)
+ continue;
+
+ save_errno = errno;
+ XLogFileName(xlogfname, tli, openLogSegNo,
+ wal_segment_size);
+ errno = save_errno;
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not write to log file %s "
+ "at offset %u, length %zu: %m",
+ xlogfname, startoffset, nleft)));
+ }
+ nleft -= written;
+ from += written;
+ startoffset += written;
+ } while (nleft > 0);
+
+ npages = 0;
+
+ /*
+ * If we just wrote the whole last page of a logfile segment,
+ * fsync the segment immediately. This avoids having to go back
+ * and re-open prior segments when an fsync request comes along
+ * later. Doing it here ensures that one and only one backend will
+ * perform this fsync.
+ *
+ * This is also the right place to notify the Archiver that the
+ * segment is ready to copy to archival storage, and to update the
+ * timer for archive_timeout, and to signal for a checkpoint if
+ * too many logfile segments have been used since the last
+ * checkpoint.
+ */
+ if (finishing_seg)
+ {
+ issue_xlog_fsync(openLogFile, openLogSegNo, tli);
+
+ /* signal that we need to wakeup walsenders later */
+ WalSndWakeupRequest();
+
+ LogwrtResult.Flush = LogwrtResult.Write; /* end of page */
+
+ if (XLogArchivingActive())
+ XLogArchiveNotifySeg(openLogSegNo, tli);
+
+ XLogCtl->lastSegSwitchTime = (pg_time_t) time(NULL);
+ XLogCtl->lastSegSwitchLSN = LogwrtResult.Flush;
+
+ /*
+ * Request a checkpoint if we've consumed too much xlog since
+ * the last one. For speed, we first check using the local
+ * copy of RedoRecPtr, which might be out of date; if it looks
+ * like a checkpoint is needed, forcibly update RedoRecPtr and
+ * recheck.
+ */
+ if (IsUnderPostmaster && XLogCheckpointNeeded(openLogSegNo))
+ {
+ (void) GetRedoRecPtr();
+ if (XLogCheckpointNeeded(openLogSegNo))
+ RequestCheckpoint(CHECKPOINT_CAUSE_XLOG);
+ }
+ }
+ }
+
+ if (ispartialpage)
+ {
+ /* Only asked to write a partial page */
+ LogwrtResult.Write = WriteRqst.Write;
+ break;
+ }
+ curridx = NextBufIdx(curridx);
+
+ /* If flexible, break out of loop as soon as we wrote something */
+ if (flexible && npages == 0)
+ break;
+ }
+
+ Assert(npages == 0);
+
+ /*
+ * If asked to flush, do so
+ */
+ if (LogwrtResult.Flush < WriteRqst.Flush &&
+ LogwrtResult.Flush < LogwrtResult.Write)
+ {
+ /*
+ * Could get here without iterating above loop, in which case we might
+ * have no open file or the wrong one. However, we do not need to
+ * fsync more than one file.
+ */
+ if (sync_method != SYNC_METHOD_OPEN &&
+ sync_method != SYNC_METHOD_OPEN_DSYNC)
+ {
+ if (openLogFile >= 0 &&
+ !XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo,
+ wal_segment_size))
+ XLogFileClose();
+ if (openLogFile < 0)
+ {
+ XLByteToPrevSeg(LogwrtResult.Write, openLogSegNo,
+ wal_segment_size);
+ openLogTLI = tli;
+ openLogFile = XLogFileOpen(openLogSegNo, tli);
+ ReserveExternalFD();
+ }
+
+ issue_xlog_fsync(openLogFile, openLogSegNo, tli);
+ }
+
+ /* signal that we need to wakeup walsenders later */
+ WalSndWakeupRequest();
+
+ LogwrtResult.Flush = LogwrtResult.Write;
+ }
+
+ /*
+ * Update shared-memory status
+ *
+ * We make sure that the shared 'request' values do not fall behind the
+ * 'result' values. This is not absolutely essential, but it saves some
+ * code in a couple of places.
+ */
+ {
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->LogwrtResult = LogwrtResult;
+ if (XLogCtl->LogwrtRqst.Write < LogwrtResult.Write)
+ XLogCtl->LogwrtRqst.Write = LogwrtResult.Write;
+ if (XLogCtl->LogwrtRqst.Flush < LogwrtResult.Flush)
+ XLogCtl->LogwrtRqst.Flush = LogwrtResult.Flush;
+ SpinLockRelease(&XLogCtl->info_lck);
+ }
+}
+
+/*
+ * Record the LSN for an asynchronous transaction commit/abort
+ * and nudge the WALWriter if there is work for it to do.
+ * (This should not be called for synchronous commits.)
+ */
+void
+XLogSetAsyncXactLSN(XLogRecPtr asyncXactLSN)
+{
+ XLogRecPtr WriteRqstPtr = asyncXactLSN;
+ bool sleeping;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ LogwrtResult = XLogCtl->LogwrtResult;
+ sleeping = XLogCtl->WalWriterSleeping;
+ if (XLogCtl->asyncXactLSN < asyncXactLSN)
+ XLogCtl->asyncXactLSN = asyncXactLSN;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * If the WALWriter is sleeping, we should kick it to make it come out of
+ * low-power mode. Otherwise, determine whether there's a full page of
+ * WAL available to write.
+ */
+ if (!sleeping)
+ {
+ /* back off to last completed page boundary */
+ WriteRqstPtr -= WriteRqstPtr % XLOG_BLCKSZ;
+
+ /* if we have already flushed that far, we're done */
+ if (WriteRqstPtr <= LogwrtResult.Flush)
+ return;
+ }
+
+ /*
+ * Nudge the WALWriter: it has a full page of WAL to write, or we want it
+ * to come out of low-power mode so that this async commit will reach disk
+ * within the expected amount of time.
+ */
+ if (ProcGlobal->walwriterLatch)
+ SetLatch(ProcGlobal->walwriterLatch);
+}
+
+/*
+ * Record the LSN up to which we can remove WAL because it's not required by
+ * any replication slot.
+ */
+void
+XLogSetReplicationSlotMinimumLSN(XLogRecPtr lsn)
+{
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->replicationSlotMinLSN = lsn;
+ SpinLockRelease(&XLogCtl->info_lck);
+}
+
+
+/*
+ * Return the oldest LSN we must retain to satisfy the needs of some
+ * replication slot.
+ */
+static XLogRecPtr
+XLogGetReplicationSlotMinimumLSN(void)
+{
+ XLogRecPtr retval;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ retval = XLogCtl->replicationSlotMinLSN;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ return retval;
+}
+
+/*
+ * Advance minRecoveryPoint in control file.
+ *
+ * If we crash during recovery, we must reach this point again before the
+ * database is consistent.
+ *
+ * If 'force' is true, 'lsn' argument is ignored. Otherwise, minRecoveryPoint
+ * is only updated if it's not already greater than or equal to 'lsn'.
+ */
+static void
+UpdateMinRecoveryPoint(XLogRecPtr lsn, bool force)
+{
+ /* Quick check using our local copy of the variable */
+ if (!updateMinRecoveryPoint || (!force && lsn <= LocalMinRecoveryPoint))
+ return;
+
+ /*
+ * An invalid minRecoveryPoint means that we need to recover all the WAL,
+ * i.e., we're doing crash recovery. We never modify the control file's
+ * value in that case, so we can short-circuit future checks here too. The
+ * local values of minRecoveryPoint and minRecoveryPointTLI should not be
+ * updated until crash recovery finishes. We only do this for the startup
+ * process as it should not update its own reference of minRecoveryPoint
+ * until it has finished crash recovery to make sure that all WAL
+ * available is replayed in this case. This also saves from extra locks
+ * taken on the control file from the startup process.
+ */
+ if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint) && InRecovery)
+ {
+ updateMinRecoveryPoint = false;
+ return;
+ }
+
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+
+ /* update local copy */
+ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint;
+ LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
+
+ if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint))
+ updateMinRecoveryPoint = false;
+ else if (force || LocalMinRecoveryPoint < lsn)
+ {
+ XLogRecPtr newMinRecoveryPoint;
+ TimeLineID newMinRecoveryPointTLI;
+
+ /*
+ * To avoid having to update the control file too often, we update it
+ * all the way to the last record being replayed, even though 'lsn'
+ * would suffice for correctness. This also allows the 'force' case
+ * to not need a valid 'lsn' value.
+ *
+ * Another important reason for doing it this way is that the passed
+ * 'lsn' value could be bogus, i.e., past the end of available WAL, if
+ * the caller got it from a corrupted heap page. Accepting such a
+ * value as the min recovery point would prevent us from coming up at
+ * all. Instead, we just log a warning and continue with recovery.
+ * (See also the comments about corrupt LSNs in XLogFlush.)
+ */
+ newMinRecoveryPoint = GetCurrentReplayRecPtr(&newMinRecoveryPointTLI);
+ if (!force && newMinRecoveryPoint < lsn)
+ elog(WARNING,
+ "xlog min recovery request %X/%X is past current point %X/%X",
+ LSN_FORMAT_ARGS(lsn), LSN_FORMAT_ARGS(newMinRecoveryPoint));
+
+ /* update control file */
+ if (ControlFile->minRecoveryPoint < newMinRecoveryPoint)
+ {
+ ControlFile->minRecoveryPoint = newMinRecoveryPoint;
+ ControlFile->minRecoveryPointTLI = newMinRecoveryPointTLI;
+ UpdateControlFile();
+ LocalMinRecoveryPoint = newMinRecoveryPoint;
+ LocalMinRecoveryPointTLI = newMinRecoveryPointTLI;
+
+ ereport(DEBUG2,
+ (errmsg_internal("updated min recovery point to %X/%X on timeline %u",
+ LSN_FORMAT_ARGS(newMinRecoveryPoint),
+ newMinRecoveryPointTLI)));
+ }
+ }
+ LWLockRelease(ControlFileLock);
+}
+
+/*
+ * Ensure that all XLOG data through the given position is flushed to disk.
+ *
+ * NOTE: this differs from XLogWrite mainly in that the WALWriteLock is not
+ * already held, and we try to avoid acquiring it if possible.
+ */
+void
+XLogFlush(XLogRecPtr record)
+{
+ XLogRecPtr WriteRqstPtr;
+ XLogwrtRqst WriteRqst;
+ TimeLineID insertTLI = XLogCtl->InsertTimeLineID;
+
+ /*
+ * During REDO, we are reading not writing WAL. Therefore, instead of
+ * trying to flush the WAL, we should update minRecoveryPoint instead. We
+ * test XLogInsertAllowed(), not InRecovery, because we need checkpointer
+ * to act this way too, and because when it tries to write the
+ * end-of-recovery checkpoint, it should indeed flush.
+ */
+ if (!XLogInsertAllowed())
+ {
+ UpdateMinRecoveryPoint(record, false);
+ return;
+ }
+
+ /* Quick exit if already known flushed */
+ if (record <= LogwrtResult.Flush)
+ return;
+
+#ifdef WAL_DEBUG
+ if (XLOG_DEBUG)
+ elog(LOG, "xlog flush request %X/%X; write %X/%X; flush %X/%X",
+ LSN_FORMAT_ARGS(record),
+ LSN_FORMAT_ARGS(LogwrtResult.Write),
+ LSN_FORMAT_ARGS(LogwrtResult.Flush));
+#endif
+
+ START_CRIT_SECTION();
+
+ /*
+ * Since fsync is usually a horribly expensive operation, we try to
+ * piggyback as much data as we can on each fsync: if we see any more data
+ * entered into the xlog buffer, we'll write and fsync that too, so that
+ * the final value of LogwrtResult.Flush is as large as possible. This
+ * gives us some chance of avoiding another fsync immediately after.
+ */
+
+ /* initialize to given target; may increase below */
+ WriteRqstPtr = record;
+
+ /*
+ * Now wait until we get the write lock, or someone else does the flush
+ * for us.
+ */
+ for (;;)
+ {
+ XLogRecPtr insertpos;
+
+ /* read LogwrtResult and update local state */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ if (WriteRqstPtr < XLogCtl->LogwrtRqst.Write)
+ WriteRqstPtr = XLogCtl->LogwrtRqst.Write;
+ LogwrtResult = XLogCtl->LogwrtResult;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /* done already? */
+ if (record <= LogwrtResult.Flush)
+ break;
+
+ /*
+ * Before actually performing the write, wait for all in-flight
+ * insertions to the pages we're about to write to finish.
+ */
+ insertpos = WaitXLogInsertionsToFinish(WriteRqstPtr);
+
+ /*
+ * Try to get the write lock. If we can't get it immediately, wait
+ * until it's released, and recheck if we still need to do the flush
+ * or if the backend that held the lock did it for us already. This
+ * helps to maintain a good rate of group committing when the system
+ * is bottlenecked by the speed of fsyncing.
+ */
+ if (!LWLockAcquireOrWait(WALWriteLock, LW_EXCLUSIVE))
+ {
+ /*
+ * The lock is now free, but we didn't acquire it yet. Before we
+ * do, loop back to check if someone else flushed the record for
+ * us already.
+ */
+ continue;
+ }
+
+ /* Got the lock; recheck whether request is satisfied */
+ LogwrtResult = XLogCtl->LogwrtResult;
+ if (record <= LogwrtResult.Flush)
+ {
+ LWLockRelease(WALWriteLock);
+ break;
+ }
+
+ /*
+ * Sleep before flush! By adding a delay here, we may give further
+ * backends the opportunity to join the backlog of group commit
+ * followers; this can significantly improve transaction throughput,
+ * at the risk of increasing transaction latency.
+ *
+ * We do not sleep if enableFsync is not turned on, nor if there are
+ * fewer than CommitSiblings other backends with active transactions.
+ */
+ if (CommitDelay > 0 && enableFsync &&
+ MinimumActiveBackends(CommitSiblings))
+ {
+ pg_usleep(CommitDelay);
+
+ /*
+ * Re-check how far we can now flush the WAL. It's generally not
+ * safe to call WaitXLogInsertionsToFinish while holding
+ * WALWriteLock, because an in-progress insertion might need to
+ * also grab WALWriteLock to make progress. But we know that all
+ * the insertions up to insertpos have already finished, because
+ * that's what the earlier WaitXLogInsertionsToFinish() returned.
+ * We're only calling it again to allow insertpos to be moved
+ * further forward, not to actually wait for anyone.
+ */
+ insertpos = WaitXLogInsertionsToFinish(insertpos);
+ }
+
+ /* try to write/flush later additions to XLOG as well */
+ WriteRqst.Write = insertpos;
+ WriteRqst.Flush = insertpos;
+
+ XLogWrite(WriteRqst, insertTLI, false);
+
+ LWLockRelease(WALWriteLock);
+ /* done */
+ break;
+ }
+
+ END_CRIT_SECTION();
+
+ /* wake up walsenders now that we've released heavily contended locks */
+ WalSndWakeupProcessRequests();
+
+ /*
+ * If we still haven't flushed to the request point then we have a
+ * problem; most likely, the requested flush point is past end of XLOG.
+ * This has been seen to occur when a disk page has a corrupted LSN.
+ *
+ * Formerly we treated this as a PANIC condition, but that hurts the
+ * system's robustness rather than helping it: we do not want to take down
+ * the whole system due to corruption on one data page. In particular, if
+ * the bad page is encountered again during recovery then we would be
+ * unable to restart the database at all! (This scenario actually
+ * happened in the field several times with 7.1 releases.) As of 8.4, bad
+ * LSNs encountered during recovery are UpdateMinRecoveryPoint's problem;
+ * the only time we can reach here during recovery is while flushing the
+ * end-of-recovery checkpoint record, and we don't expect that to have a
+ * bad LSN.
+ *
+ * Note that for calls from xact.c, the ERROR will be promoted to PANIC
+ * since xact.c calls this routine inside a critical section. However,
+ * calls from bufmgr.c are not within critical sections and so we will not
+ * force a restart for a bad LSN on a data page.
+ */
+ if (LogwrtResult.Flush < record)
+ elog(ERROR,
+ "xlog flush request %X/%X is not satisfied --- flushed only to %X/%X",
+ LSN_FORMAT_ARGS(record),
+ LSN_FORMAT_ARGS(LogwrtResult.Flush));
+}
+
+/*
+ * Write & flush xlog, but without specifying exactly where to.
+ *
+ * We normally write only completed blocks; but if there is nothing to do on
+ * that basis, we check for unwritten async commits in the current incomplete
+ * block, and write through the latest one of those. Thus, if async commits
+ * are not being used, we will write complete blocks only.
+ *
+ * If, based on the above, there's anything to write we do so immediately. But
+ * to avoid calling fsync, fdatasync et. al. at a rate that'd impact
+ * concurrent IO, we only flush WAL every wal_writer_delay ms, or if there's
+ * more than wal_writer_flush_after unflushed blocks.
+ *
+ * We can guarantee that async commits reach disk after at most three
+ * wal_writer_delay cycles. (When flushing complete blocks, we allow XLogWrite
+ * to write "flexibly", meaning it can stop at the end of the buffer ring;
+ * this makes a difference only with very high load or long wal_writer_delay,
+ * but imposes one extra cycle for the worst case for async commits.)
+ *
+ * This routine is invoked periodically by the background walwriter process.
+ *
+ * Returns true if there was any work to do, even if we skipped flushing due
+ * to wal_writer_delay/wal_writer_flush_after.
+ */
+bool
+XLogBackgroundFlush(void)
+{
+ XLogwrtRqst WriteRqst;
+ bool flexible = true;
+ static TimestampTz lastflush;
+ TimestampTz now;
+ int flushbytes;
+ TimeLineID insertTLI;
+
+ /* XLOG doesn't need flushing during recovery */
+ if (RecoveryInProgress())
+ return false;
+
+ /*
+ * Since we're not in recovery, InsertTimeLineID is set and can't change,
+ * so we can read it without a lock.
+ */
+ insertTLI = XLogCtl->InsertTimeLineID;
+
+ /* read LogwrtResult and update local state */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ LogwrtResult = XLogCtl->LogwrtResult;
+ WriteRqst = XLogCtl->LogwrtRqst;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /* back off to last completed page boundary */
+ WriteRqst.Write -= WriteRqst.Write % XLOG_BLCKSZ;
+
+ /* if we have already flushed that far, consider async commit records */
+ if (WriteRqst.Write <= LogwrtResult.Flush)
+ {
+ SpinLockAcquire(&XLogCtl->info_lck);
+ WriteRqst.Write = XLogCtl->asyncXactLSN;
+ SpinLockRelease(&XLogCtl->info_lck);
+ flexible = false; /* ensure it all gets written */
+ }
+
+ /*
+ * If already known flushed, we're done. Just need to check if we are
+ * holding an open file handle to a logfile that's no longer in use,
+ * preventing the file from being deleted.
+ */
+ if (WriteRqst.Write <= LogwrtResult.Flush)
+ {
+ if (openLogFile >= 0)
+ {
+ if (!XLByteInPrevSeg(LogwrtResult.Write, openLogSegNo,
+ wal_segment_size))
+ {
+ XLogFileClose();
+ }
+ }
+ return false;
+ }
+
+ /*
+ * Determine how far to flush WAL, based on the wal_writer_delay and
+ * wal_writer_flush_after GUCs.
+ */
+ now = GetCurrentTimestamp();
+ flushbytes =
+ WriteRqst.Write / XLOG_BLCKSZ - LogwrtResult.Flush / XLOG_BLCKSZ;
+
+ if (WalWriterFlushAfter == 0 || lastflush == 0)
+ {
+ /* first call, or block based limits disabled */
+ WriteRqst.Flush = WriteRqst.Write;
+ lastflush = now;
+ }
+ else if (TimestampDifferenceExceeds(lastflush, now, WalWriterDelay))
+ {
+ /*
+ * Flush the writes at least every WalWriterDelay ms. This is
+ * important to bound the amount of time it takes for an asynchronous
+ * commit to hit disk.
+ */
+ WriteRqst.Flush = WriteRqst.Write;
+ lastflush = now;
+ }
+ else if (flushbytes >= WalWriterFlushAfter)
+ {
+ /* exceeded wal_writer_flush_after blocks, flush */
+ WriteRqst.Flush = WriteRqst.Write;
+ lastflush = now;
+ }
+ else
+ {
+ /* no flushing, this time round */
+ WriteRqst.Flush = 0;
+ }
+
+#ifdef WAL_DEBUG
+ if (XLOG_DEBUG)
+ elog(LOG, "xlog bg flush request write %X/%X; flush: %X/%X, current is write %X/%X; flush %X/%X",
+ LSN_FORMAT_ARGS(WriteRqst.Write),
+ LSN_FORMAT_ARGS(WriteRqst.Flush),
+ LSN_FORMAT_ARGS(LogwrtResult.Write),
+ LSN_FORMAT_ARGS(LogwrtResult.Flush));
+#endif
+
+ START_CRIT_SECTION();
+
+ /* now wait for any in-progress insertions to finish and get write lock */
+ WaitXLogInsertionsToFinish(WriteRqst.Write);
+ LWLockAcquire(WALWriteLock, LW_EXCLUSIVE);
+ LogwrtResult = XLogCtl->LogwrtResult;
+ if (WriteRqst.Write > LogwrtResult.Write ||
+ WriteRqst.Flush > LogwrtResult.Flush)
+ {
+ XLogWrite(WriteRqst, insertTLI, flexible);
+ }
+ LWLockRelease(WALWriteLock);
+
+ END_CRIT_SECTION();
+
+ /* wake up walsenders now that we've released heavily contended locks */
+ WalSndWakeupProcessRequests();
+
+ /*
+ * Great, done. To take some work off the critical path, try to initialize
+ * as many of the no-longer-needed WAL buffers for future use as we can.
+ */
+ AdvanceXLInsertBuffer(InvalidXLogRecPtr, insertTLI, true);
+
+ /*
+ * If we determined that we need to write data, but somebody else
+ * wrote/flushed already, it should be considered as being active, to
+ * avoid hibernating too early.
+ */
+ return true;
+}
+
+/*
+ * Test whether XLOG data has been flushed up to (at least) the given position.
+ *
+ * Returns true if a flush is still needed. (It may be that someone else
+ * is already in process of flushing that far, however.)
+ */
+bool
+XLogNeedsFlush(XLogRecPtr record)
+{
+ /*
+ * During recovery, we don't flush WAL but update minRecoveryPoint
+ * instead. So "needs flush" is taken to mean whether minRecoveryPoint
+ * would need to be updated.
+ */
+ if (RecoveryInProgress())
+ {
+ /*
+ * An invalid minRecoveryPoint means that we need to recover all the
+ * WAL, i.e., we're doing crash recovery. We never modify the control
+ * file's value in that case, so we can short-circuit future checks
+ * here too. This triggers a quick exit path for the startup process,
+ * which cannot update its local copy of minRecoveryPoint as long as
+ * it has not replayed all WAL available when doing crash recovery.
+ */
+ if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint) && InRecovery)
+ updateMinRecoveryPoint = false;
+
+ /* Quick exit if already known to be updated or cannot be updated */
+ if (record <= LocalMinRecoveryPoint || !updateMinRecoveryPoint)
+ return false;
+
+ /*
+ * Update local copy of minRecoveryPoint. But if the lock is busy,
+ * just return a conservative guess.
+ */
+ if (!LWLockConditionalAcquire(ControlFileLock, LW_SHARED))
+ return true;
+ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint;
+ LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
+ LWLockRelease(ControlFileLock);
+
+ /*
+ * Check minRecoveryPoint for any other process than the startup
+ * process doing crash recovery, which should not update the control
+ * file value if crash recovery is still running.
+ */
+ if (XLogRecPtrIsInvalid(LocalMinRecoveryPoint))
+ updateMinRecoveryPoint = false;
+
+ /* check again */
+ if (record <= LocalMinRecoveryPoint || !updateMinRecoveryPoint)
+ return false;
+ else
+ return true;
+ }
+
+ /* Quick exit if already known flushed */
+ if (record <= LogwrtResult.Flush)
+ return false;
+
+ /* read LogwrtResult and update local state */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ LogwrtResult = XLogCtl->LogwrtResult;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /* check again */
+ if (record <= LogwrtResult.Flush)
+ return false;
+
+ return true;
+}
+
+/*
+ * Try to make a given XLOG file segment exist.
+ *
+ * logsegno: identify segment.
+ *
+ * *added: on return, true if this call raised the number of extant segments.
+ *
+ * path: on return, this char[MAXPGPATH] has the path to the logsegno file.
+ *
+ * Returns -1 or FD of opened file. A -1 here is not an error; a caller
+ * wanting an open segment should attempt to open "path", which usually will
+ * succeed. (This is weird, but it's efficient for the callers.)
+ */
+static int
+XLogFileInitInternal(XLogSegNo logsegno, TimeLineID logtli,
+ bool *added, char *path)
+{
+ char tmppath[MAXPGPATH];
+ PGAlignedXLogBlock zbuffer;
+ XLogSegNo installed_segno;
+ XLogSegNo max_segno;
+ int fd;
+ int save_errno;
+
+ Assert(logtli != 0);
+
+ XLogFilePath(path, logtli, logsegno, wal_segment_size);
+
+ /*
+ * Try to use existent file (checkpoint maker may have created it already)
+ */
+ *added = false;
+ fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
+ if (fd < 0)
+ {
+ if (errno != ENOENT)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m", path)));
+ }
+ else
+ return fd;
+
+ /*
+ * Initialize an empty (all zeroes) segment. NOTE: it is possible that
+ * another process is doing the same thing. If so, we will end up
+ * pre-creating an extra log segment. That seems OK, and better than
+ * holding the lock throughout this lengthy process.
+ */
+ elog(DEBUG2, "creating and filling new WAL file");
+
+ snprintf(tmppath, MAXPGPATH, XLOGDIR "/xlogtemp.%d", (int) getpid());
+
+ unlink(tmppath);
+
+ /* do not use get_sync_bit() here --- want to fsync only at end of fill */
+ fd = BasicOpenFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
+ if (fd < 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not create file \"%s\": %m", tmppath)));
+
+ memset(zbuffer.data, 0, XLOG_BLCKSZ);
+
+ pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_WRITE);
+ save_errno = 0;
+ if (wal_init_zero)
+ {
+ struct iovec iov[PG_IOV_MAX];
+ int blocks;
+
+ /*
+ * Zero-fill the file. With this setting, we do this the hard way to
+ * ensure that all the file space has really been allocated. On
+ * platforms that allow "holes" in files, just seeking to the end
+ * doesn't allocate intermediate space. This way, we know that we
+ * have all the space and (after the fsync below) that all the
+ * indirect blocks are down on disk. Therefore, fdatasync(2) or
+ * O_DSYNC will be sufficient to sync future writes to the log file.
+ */
+
+ /* Prepare to write out a lot of copies of our zero buffer at once. */
+ for (int i = 0; i < lengthof(iov); ++i)
+ {
+ iov[i].iov_base = zbuffer.data;
+ iov[i].iov_len = XLOG_BLCKSZ;
+ }
+
+ /* Loop, writing as many blocks as we can for each system call. */
+ blocks = wal_segment_size / XLOG_BLCKSZ;
+ for (int i = 0; i < blocks;)
+ {
+ int iovcnt = Min(blocks - i, lengthof(iov));
+ off_t offset = i * XLOG_BLCKSZ;
+
+ if (pg_pwritev_with_retry(fd, iov, iovcnt, offset) < 0)
+ {
+ save_errno = errno;
+ break;
+ }
+
+ i += iovcnt;
+ }
+ }
+ else
+ {
+ /*
+ * Otherwise, seeking to the end and writing a solitary byte is
+ * enough.
+ */
+ errno = 0;
+ if (pg_pwrite(fd, zbuffer.data, 1, wal_segment_size - 1) != 1)
+ {
+ /* if write didn't set errno, assume no disk space */
+ save_errno = errno ? errno : ENOSPC;
+ }
+ }
+ pgstat_report_wait_end();
+
+ if (save_errno)
+ {
+ /*
+ * If we fail to make the file, delete it to release disk space
+ */
+ unlink(tmppath);
+
+ close(fd);
+
+ errno = save_errno;
+
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not write to file \"%s\": %m", tmppath)));
+ }
+
+ pgstat_report_wait_start(WAIT_EVENT_WAL_INIT_SYNC);
+ if (pg_fsync(fd) != 0)
+ {
+ int save_errno = errno;
+
+ close(fd);
+ errno = save_errno;
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not fsync file \"%s\": %m", tmppath)));
+ }
+ pgstat_report_wait_end();
+
+ if (close(fd) != 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not close file \"%s\": %m", tmppath)));
+
+ /*
+ * Now move the segment into place with its final name. Cope with
+ * possibility that someone else has created the file while we were
+ * filling ours: if so, use ours to pre-create a future log segment.
+ */
+ installed_segno = logsegno;
+
+ /*
+ * XXX: What should we use as max_segno? We used to use XLOGfileslop when
+ * that was a constant, but that was always a bit dubious: normally, at a
+ * checkpoint, XLOGfileslop was the offset from the checkpoint record, but
+ * here, it was the offset from the insert location. We can't do the
+ * normal XLOGfileslop calculation here because we don't have access to
+ * the prior checkpoint's redo location. So somewhat arbitrarily, just use
+ * CheckPointSegments.
+ */
+ max_segno = logsegno + CheckPointSegments;
+ if (InstallXLogFileSegment(&installed_segno, tmppath, true, max_segno,
+ logtli))
+ {
+ *added = true;
+ elog(DEBUG2, "done creating and filling new WAL file");
+ }
+ else
+ {
+ /*
+ * No need for any more future segments, or InstallXLogFileSegment()
+ * failed to rename the file into place. If the rename failed, a
+ * caller opening the file may fail.
+ */
+ unlink(tmppath);
+ elog(DEBUG2, "abandoned new WAL file");
+ }
+
+ return -1;
+}
+
+/*
+ * Create a new XLOG file segment, or open a pre-existing one.
+ *
+ * logsegno: identify segment to be created/opened.
+ *
+ * Returns FD of opened file.
+ *
+ * Note: errors here are ERROR not PANIC because we might or might not be
+ * inside a critical section (eg, during checkpoint there is no reason to
+ * take down the system on failure). They will promote to PANIC if we are
+ * in a critical section.
+ */
+int
+XLogFileInit(XLogSegNo logsegno, TimeLineID logtli)
+{
+ bool ignore_added;
+ char path[MAXPGPATH];
+ int fd;
+
+ Assert(logtli != 0);
+
+ fd = XLogFileInitInternal(logsegno, logtli, &ignore_added, path);
+ if (fd >= 0)
+ return fd;
+
+ /* Now open original target segment (might not be file I just made) */
+ fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
+ if (fd < 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m", path)));
+ return fd;
+}
+
+/*
+ * Create a new XLOG file segment by copying a pre-existing one.
+ *
+ * destsegno: identify segment to be created.
+ *
+ * srcTLI, srcsegno: identify segment to be copied (could be from
+ * a different timeline)
+ *
+ * upto: how much of the source file to copy (the rest is filled with
+ * zeros)
+ *
+ * Currently this is only used during recovery, and so there are no locking
+ * considerations. But we should be just as tense as XLogFileInit to avoid
+ * emplacing a bogus file.
+ */
+static void
+XLogFileCopy(TimeLineID destTLI, XLogSegNo destsegno,
+ TimeLineID srcTLI, XLogSegNo srcsegno,
+ int upto)
+{
+ char path[MAXPGPATH];
+ char tmppath[MAXPGPATH];
+ PGAlignedXLogBlock buffer;
+ int srcfd;
+ int fd;
+ int nbytes;
+
+ /*
+ * Open the source file
+ */
+ XLogFilePath(path, srcTLI, srcsegno, wal_segment_size);
+ srcfd = OpenTransientFile(path, O_RDONLY | PG_BINARY);
+ if (srcfd < 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m", path)));
+
+ /*
+ * Copy into a temp file name.
+ */
+ snprintf(tmppath, MAXPGPATH, XLOGDIR "/xlogtemp.%d", (int) getpid());
+
+ unlink(tmppath);
+
+ /* do not use get_sync_bit() here --- want to fsync only at end of fill */
+ fd = OpenTransientFile(tmppath, O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
+ if (fd < 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not create file \"%s\": %m", tmppath)));
+
+ /*
+ * Do the data copying.
+ */
+ for (nbytes = 0; nbytes < wal_segment_size; nbytes += sizeof(buffer))
+ {
+ int nread;
+
+ nread = upto - nbytes;
+
+ /*
+ * The part that is not read from the source file is filled with
+ * zeros.
+ */
+ if (nread < sizeof(buffer))
+ memset(buffer.data, 0, sizeof(buffer));
+
+ if (nread > 0)
+ {
+ int r;
+
+ if (nread > sizeof(buffer))
+ nread = sizeof(buffer);
+ pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_READ);
+ r = read(srcfd, buffer.data, nread);
+ if (r != nread)
+ {
+ if (r < 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not read file \"%s\": %m",
+ path)));
+ else
+ ereport(ERROR,
+ (errcode(ERRCODE_DATA_CORRUPTED),
+ errmsg("could not read file \"%s\": read %d of %zu",
+ path, r, (Size) nread)));
+ }
+ pgstat_report_wait_end();
+ }
+ errno = 0;
+ pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_WRITE);
+ if ((int) write(fd, buffer.data, sizeof(buffer)) != (int) sizeof(buffer))
+ {
+ int save_errno = errno;
+
+ /*
+ * If we fail to make the file, delete it to release disk space
+ */
+ unlink(tmppath);
+ /* if write didn't set errno, assume problem is no disk space */
+ errno = save_errno ? save_errno : ENOSPC;
+
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not write to file \"%s\": %m", tmppath)));
+ }
+ pgstat_report_wait_end();
+ }
+
+ pgstat_report_wait_start(WAIT_EVENT_WAL_COPY_SYNC);
+ if (pg_fsync(fd) != 0)
+ ereport(data_sync_elevel(ERROR),
+ (errcode_for_file_access(),
+ errmsg("could not fsync file \"%s\": %m", tmppath)));
+ pgstat_report_wait_end();
+
+ if (CloseTransientFile(fd) != 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not close file \"%s\": %m", tmppath)));
+
+ if (CloseTransientFile(srcfd) != 0)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not close file \"%s\": %m", path)));
+
+ /*
+ * Now move the segment into place with its final name.
+ */
+ if (!InstallXLogFileSegment(&destsegno, tmppath, false, 0, destTLI))
+ elog(ERROR, "InstallXLogFileSegment should not have failed");
+}
+
+/*
+ * Install a new XLOG segment file as a current or future log segment.
+ *
+ * This is used both to install a newly-created segment (which has a temp
+ * filename while it's being created) and to recycle an old segment.
+ *
+ * *segno: identify segment to install as (or first possible target).
+ * When find_free is true, this is modified on return to indicate the
+ * actual installation location or last segment searched.
+ *
+ * tmppath: initial name of file to install. It will be renamed into place.
+ *
+ * find_free: if true, install the new segment at the first empty segno
+ * number at or after the passed numbers. If false, install the new segment
+ * exactly where specified, deleting any existing segment file there.
+ *
+ * max_segno: maximum segment number to install the new file as. Fail if no
+ * free slot is found between *segno and max_segno. (Ignored when find_free
+ * is false.)
+ *
+ * tli: The timeline on which the new segment should be installed.
+ *
+ * Returns true if the file was installed successfully. false indicates that
+ * max_segno limit was exceeded, the startup process has disabled this
+ * function for now, or an error occurred while renaming the file into place.
+ */
+static bool
+InstallXLogFileSegment(XLogSegNo *segno, char *tmppath,
+ bool find_free, XLogSegNo max_segno, TimeLineID tli)
+{
+ char path[MAXPGPATH];
+ struct stat stat_buf;
+
+ Assert(tli != 0);
+
+ XLogFilePath(path, tli, *segno, wal_segment_size);
+
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ if (!XLogCtl->InstallXLogFileSegmentActive)
+ {
+ LWLockRelease(ControlFileLock);
+ return false;
+ }
+
+ if (!find_free)
+ {
+ /* Force installation: get rid of any pre-existing segment file */
+ durable_unlink(path, DEBUG1);
+ }
+ else
+ {
+ /* Find a free slot to put it in */
+ while (stat(path, &stat_buf) == 0)
+ {
+ if ((*segno) >= max_segno)
+ {
+ /* Failed to find a free slot within specified range */
+ LWLockRelease(ControlFileLock);
+ return false;
+ }
+ (*segno)++;
+ XLogFilePath(path, tli, *segno, wal_segment_size);
+ }
+ }
+
+ /*
+ * Perform the rename using link if available, paranoidly trying to avoid
+ * overwriting an existing file (there shouldn't be one).
+ */
+ if (durable_rename_excl(tmppath, path, LOG) != 0)
+ {
+ LWLockRelease(ControlFileLock);
+ /* durable_rename_excl already emitted log message */
+ return false;
+ }
+
+ LWLockRelease(ControlFileLock);
+
+ return true;
+}
+
+/*
+ * Open a pre-existing logfile segment for writing.
+ */
+int
+XLogFileOpen(XLogSegNo segno, TimeLineID tli)
+{
+ char path[MAXPGPATH];
+ int fd;
+
+ XLogFilePath(path, tli, segno, wal_segment_size);
+
+ fd = BasicOpenFile(path, O_RDWR | PG_BINARY | get_sync_bit(sync_method));
+ if (fd < 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m", path)));
+
+ return fd;
+}
+
+/*
+ * Close the current logfile segment for writing.
+ */
+static void
+XLogFileClose(void)
+{
+ Assert(openLogFile >= 0);
+
+ /*
+ * WAL segment files will not be re-read in normal operation, so we advise
+ * the OS to release any cached pages. But do not do so if WAL archiving
+ * or streaming is active, because archiver and walsender process could
+ * use the cache to read the WAL segment.
+ */
+#if defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED)
+ if (!XLogIsNeeded())
+ (void) posix_fadvise(openLogFile, 0, 0, POSIX_FADV_DONTNEED);
+#endif
+
+ if (close(openLogFile) != 0)
+ {
+ char xlogfname[MAXFNAMELEN];
+ int save_errno = errno;
+
+ XLogFileName(xlogfname, openLogTLI, openLogSegNo, wal_segment_size);
+ errno = save_errno;
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not close file \"%s\": %m", xlogfname)));
+ }
+
+ openLogFile = -1;
+ ReleaseExternalFD();
+}
+
+/*
+ * Preallocate log files beyond the specified log endpoint.
+ *
+ * XXX this is currently extremely conservative, since it forces only one
+ * future log segment to exist, and even that only if we are 75% done with
+ * the current one. This is only appropriate for very low-WAL-volume systems.
+ * High-volume systems will be OK once they've built up a sufficient set of
+ * recycled log segments, but the startup transient is likely to include
+ * a lot of segment creations by foreground processes, which is not so good.
+ *
+ * XLogFileInitInternal() can ereport(ERROR). All known causes indicate big
+ * trouble; for example, a full filesystem is one cause. The checkpoint WAL
+ * and/or ControlFile updates already completed. If a RequestCheckpoint()
+ * initiated the present checkpoint and an ERROR ends this function, the
+ * command that called RequestCheckpoint() fails. That's not ideal, but it's
+ * not worth contorting more functions to use caller-specified elevel values.
+ * (With or without RequestCheckpoint(), an ERROR forestalls some inessential
+ * reporting and resource reclamation.)
+ */
+static void
+PreallocXlogFiles(XLogRecPtr endptr, TimeLineID tli)
+{
+ XLogSegNo _logSegNo;
+ int lf;
+ bool added;
+ char path[MAXPGPATH];
+ uint64 offset;
+
+ if (!XLogCtl->InstallXLogFileSegmentActive)
+ return; /* unlocked check says no */
+
+ XLByteToPrevSeg(endptr, _logSegNo, wal_segment_size);
+ offset = XLogSegmentOffset(endptr - 1, wal_segment_size);
+ if (offset >= (uint32) (0.75 * wal_segment_size))
+ {
+ _logSegNo++;
+ lf = XLogFileInitInternal(_logSegNo, tli, &added, path);
+ if (lf >= 0)
+ close(lf);
+ if (added)
+ CheckpointStats.ckpt_segs_added++;
+ }
+}
+
+/*
+ * Throws an error if the given log segment has already been removed or
+ * recycled. The caller should only pass a segment that it knows to have
+ * existed while the server has been running, as this function always
+ * succeeds if no WAL segments have been removed since startup.
+ * 'tli' is only used in the error message.
+ *
+ * Note: this function guarantees to keep errno unchanged on return.
+ * This supports callers that use this to possibly deliver a better
+ * error message about a missing file, while still being able to throw
+ * a normal file-access error afterwards, if this does return.
+ */
+void
+CheckXLogRemoved(XLogSegNo segno, TimeLineID tli)
+{
+ int save_errno = errno;
+ XLogSegNo lastRemovedSegNo;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ lastRemovedSegNo = XLogCtl->lastRemovedSegNo;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ if (segno <= lastRemovedSegNo)
+ {
+ char filename[MAXFNAMELEN];
+
+ XLogFileName(filename, tli, segno, wal_segment_size);
+ errno = save_errno;
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("requested WAL segment %s has already been removed",
+ filename)));
+ }
+ errno = save_errno;
+}
+
+/*
+ * Return the last WAL segment removed, or 0 if no segment has been removed
+ * since startup.
+ *
+ * NB: the result can be out of date arbitrarily fast, the caller has to deal
+ * with that.
+ */
+XLogSegNo
+XLogGetLastRemovedSegno(void)
+{
+ XLogSegNo lastRemovedSegNo;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ lastRemovedSegNo = XLogCtl->lastRemovedSegNo;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ return lastRemovedSegNo;
+}
+
+
+/*
+ * Update the last removed segno pointer in shared memory, to reflect that the
+ * given XLOG file has been removed.
+ */
+static void
+UpdateLastRemovedPtr(char *filename)
+{
+ uint32 tli;
+ XLogSegNo segno;
+
+ XLogFromFileName(filename, &tli, &segno, wal_segment_size);
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ if (segno > XLogCtl->lastRemovedSegNo)
+ XLogCtl->lastRemovedSegNo = segno;
+ SpinLockRelease(&XLogCtl->info_lck);
+}
+
+/*
+ * Remove all temporary log files in pg_wal
+ *
+ * This is called at the beginning of recovery after a previous crash,
+ * at a point where no other processes write fresh WAL data.
+ */
+static void
+RemoveTempXlogFiles(void)
+{
+ DIR *xldir;
+ struct dirent *xlde;
+
+ elog(DEBUG2, "removing all temporary WAL segments");
+
+ xldir = AllocateDir(XLOGDIR);
+ while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL)
+ {
+ char path[MAXPGPATH];
+
+ if (strncmp(xlde->d_name, "xlogtemp.", 9) != 0)
+ continue;
+
+ snprintf(path, MAXPGPATH, XLOGDIR "/%s", xlde->d_name);
+ unlink(path);
+ elog(DEBUG2, "removed temporary WAL segment \"%s\"", path);
+ }
+ FreeDir(xldir);
+}
+
+/*
+ * Recycle or remove all log files older or equal to passed segno.
+ *
+ * endptr is current (or recent) end of xlog, and lastredoptr is the
+ * redo pointer of the last checkpoint. These are used to determine
+ * whether we want to recycle rather than delete no-longer-wanted log files.
+ *
+ * insertTLI is the current timeline for XLOG insertion. Any recycled
+ * segments should be reused for this timeline.
+ */
+static void
+RemoveOldXlogFiles(XLogSegNo segno, XLogRecPtr lastredoptr, XLogRecPtr endptr,
+ TimeLineID insertTLI)
+{
+ DIR *xldir;
+ struct dirent *xlde;
+ char lastoff[MAXFNAMELEN];
+ XLogSegNo endlogSegNo;
+ XLogSegNo recycleSegNo;
+
+ /* Initialize info about where to try to recycle to */
+ XLByteToSeg(endptr, endlogSegNo, wal_segment_size);
+ recycleSegNo = XLOGfileslop(lastredoptr);
+
+ /*
+ * Construct a filename of the last segment to be kept. The timeline ID
+ * doesn't matter, we ignore that in the comparison. (During recovery,
+ * InsertTimeLineID isn't set, so we can't use that.)
+ */
+ XLogFileName(lastoff, 0, segno, wal_segment_size);
+
+ elog(DEBUG2, "attempting to remove WAL segments older than log file %s",
+ lastoff);
+
+ xldir = AllocateDir(XLOGDIR);
+
+ while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL)
+ {
+ /* Ignore files that are not XLOG segments */
+ if (!IsXLogFileName(xlde->d_name) &&
+ !IsPartialXLogFileName(xlde->d_name))
+ continue;
+
+ /*
+ * We ignore the timeline part of the XLOG segment identifiers in
+ * deciding whether a segment is still needed. This ensures that we
+ * won't prematurely remove a segment from a parent timeline. We could
+ * probably be a little more proactive about removing segments of
+ * non-parent timelines, but that would be a whole lot more
+ * complicated.
+ *
+ * We use the alphanumeric sorting property of the filenames to decide
+ * which ones are earlier than the lastoff segment.
+ */
+ if (strcmp(xlde->d_name + 8, lastoff + 8) <= 0)
+ {
+ if (XLogArchiveCheckDone(xlde->d_name))
+ {
+ /* Update the last removed location in shared memory first */
+ UpdateLastRemovedPtr(xlde->d_name);
+
+ RemoveXlogFile(xlde->d_name, recycleSegNo, &endlogSegNo,
+ insertTLI);
+ }
+ }
+ }
+
+ FreeDir(xldir);
+}
+
+/*
+ * Remove WAL files that are not part of the given timeline's history.
+ *
+ * This is called during recovery, whenever we switch to follow a new
+ * timeline, and at the end of recovery when we create a new timeline. We
+ * wouldn't otherwise care about extra WAL files lying in pg_wal, but they
+ * might be leftover pre-allocated or recycled WAL segments on the old timeline
+ * that we haven't used yet, and contain garbage. If we just leave them in
+ * pg_wal, they will eventually be archived, and we can't let that happen.
+ * Files that belong to our timeline history are valid, because we have
+ * successfully replayed them, but from others we can't be sure.
+ *
+ * 'switchpoint' is the current point in WAL where we switch to new timeline,
+ * and 'newTLI' is the new timeline we switch to.
+ */
+void
+RemoveNonParentXlogFiles(XLogRecPtr switchpoint, TimeLineID newTLI)
+{
+ DIR *xldir;
+ struct dirent *xlde;
+ char switchseg[MAXFNAMELEN];
+ XLogSegNo endLogSegNo;
+ XLogSegNo switchLogSegNo;
+ XLogSegNo recycleSegNo;
+
+ /*
+ * Initialize info about where to begin the work. This will recycle,
+ * somewhat arbitrarily, 10 future segments.
+ */
+ XLByteToPrevSeg(switchpoint, switchLogSegNo, wal_segment_size);
+ XLByteToSeg(switchpoint, endLogSegNo, wal_segment_size);
+ recycleSegNo = endLogSegNo + 10;
+
+ /*
+ * Construct a filename of the last segment to be kept.
+ */
+ XLogFileName(switchseg, newTLI, switchLogSegNo, wal_segment_size);
+
+ elog(DEBUG2, "attempting to remove WAL segments newer than log file %s",
+ switchseg);
+
+ xldir = AllocateDir(XLOGDIR);
+
+ while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL)
+ {
+ /* Ignore files that are not XLOG segments */
+ if (!IsXLogFileName(xlde->d_name))
+ continue;
+
+ /*
+ * Remove files that are on a timeline older than the new one we're
+ * switching to, but with a segment number >= the first segment on the
+ * new timeline.
+ */
+ if (strncmp(xlde->d_name, switchseg, 8) < 0 &&
+ strcmp(xlde->d_name + 8, switchseg + 8) > 0)
+ {
+ /*
+ * If the file has already been marked as .ready, however, don't
+ * remove it yet. It should be OK to remove it - files that are
+ * not part of our timeline history are not required for recovery
+ * - but seems safer to let them be archived and removed later.
+ */
+ if (!XLogArchiveIsReady(xlde->d_name))
+ RemoveXlogFile(xlde->d_name, recycleSegNo, &endLogSegNo,
+ newTLI);
+ }
+ }
+
+ FreeDir(xldir);
+}
+
+/*
+ * Recycle or remove a log file that's no longer needed.
+ *
+ * segname is the name of the segment to recycle or remove. recycleSegNo
+ * is the segment number to recycle up to. endlogSegNo is the segment
+ * number of the current (or recent) end of WAL.
+ *
+ * endlogSegNo gets incremented if the segment is recycled so as it is not
+ * checked again with future callers of this function.
+ *
+ * insertTLI is the current timeline for XLOG insertion. Any recycled segments
+ * should be used for this timeline.
+ */
+static void
+RemoveXlogFile(const char *segname, XLogSegNo recycleSegNo,
+ XLogSegNo *endlogSegNo, TimeLineID insertTLI)
+{
+ char path[MAXPGPATH];
+#ifdef WIN32
+ char newpath[MAXPGPATH];
+#endif
+ struct stat statbuf;
+
+ snprintf(path, MAXPGPATH, XLOGDIR "/%s", segname);
+
+ /*
+ * Before deleting the file, see if it can be recycled as a future log
+ * segment. Only recycle normal files, because we don't want to recycle
+ * symbolic links pointing to a separate archive directory.
+ */
+ if (wal_recycle &&
+ *endlogSegNo <= recycleSegNo &&
+ XLogCtl->InstallXLogFileSegmentActive && /* callee rechecks this */
+ lstat(path, &statbuf) == 0 && S_ISREG(statbuf.st_mode) &&
+ InstallXLogFileSegment(endlogSegNo, path,
+ true, recycleSegNo, insertTLI))
+ {
+ ereport(DEBUG2,
+ (errmsg_internal("recycled write-ahead log file \"%s\"",
+ segname)));
+ CheckpointStats.ckpt_segs_recycled++;
+ /* Needn't recheck that slot on future iterations */
+ (*endlogSegNo)++;
+ }
+ else
+ {
+ /* No need for any more future segments, or recycling failed ... */
+ int rc;
+
+ ereport(DEBUG2,
+ (errmsg_internal("removing write-ahead log file \"%s\"",
+ segname)));
+
+#ifdef WIN32
+
+ /*
+ * On Windows, if another process (e.g another backend) holds the file
+ * open in FILE_SHARE_DELETE mode, unlink will succeed, but the file
+ * will still show up in directory listing until the last handle is
+ * closed. To avoid confusing the lingering deleted file for a live
+ * WAL file that needs to be archived, rename it before deleting it.
+ *
+ * If another process holds the file open without FILE_SHARE_DELETE
+ * flag, rename will fail. We'll try again at the next checkpoint.
+ */
+ snprintf(newpath, MAXPGPATH, "%s.deleted", path);
+ if (rename(path, newpath) != 0)
+ {
+ ereport(LOG,
+ (errcode_for_file_access(),
+ errmsg("could not rename file \"%s\": %m",
+ path)));
+ return;
+ }
+ rc = durable_unlink(newpath, LOG);
+#else
+ rc = durable_unlink(path, LOG);
+#endif
+ if (rc != 0)
+ {
+ /* Message already logged by durable_unlink() */
+ return;
+ }
+ CheckpointStats.ckpt_segs_removed++;
+ }
+
+ XLogArchiveCleanup(segname);
+}
+
+/*
+ * Verify whether pg_wal and pg_wal/archive_status exist.
+ * If the latter does not exist, recreate it.
+ *
+ * It is not the goal of this function to verify the contents of these
+ * directories, but to help in cases where someone has performed a cluster
+ * copy for PITR purposes but omitted pg_wal from the copy.
+ *
+ * We could also recreate pg_wal if it doesn't exist, but a deliberate
+ * policy decision was made not to. It is fairly common for pg_wal to be
+ * a symlink, and if that was the DBA's intent then automatically making a
+ * plain directory would result in degraded performance with no notice.
+ */
+static void
+ValidateXLOGDirectoryStructure(void)
+{
+ char path[MAXPGPATH];
+ struct stat stat_buf;
+
+ /* Check for pg_wal; if it doesn't exist, error out */
+ if (stat(XLOGDIR, &stat_buf) != 0 ||
+ !S_ISDIR(stat_buf.st_mode))
+ ereport(FATAL,
+ (errmsg("required WAL directory \"%s\" does not exist",
+ XLOGDIR)));
+
+ /* Check for archive_status */
+ snprintf(path, MAXPGPATH, XLOGDIR "/archive_status");
+ if (stat(path, &stat_buf) == 0)
+ {
+ /* Check for weird cases where it exists but isn't a directory */
+ if (!S_ISDIR(stat_buf.st_mode))
+ ereport(FATAL,
+ (errmsg("required WAL directory \"%s\" does not exist",
+ path)));
+ }
+ else
+ {
+ ereport(LOG,
+ (errmsg("creating missing WAL directory \"%s\"", path)));
+ if (MakePGDirectory(path) < 0)
+ ereport(FATAL,
+ (errmsg("could not create missing directory \"%s\": %m",
+ path)));
+ }
+}
+
+/*
+ * Remove previous backup history files. This also retries creation of
+ * .ready files for any backup history files for which XLogArchiveNotify
+ * failed earlier.
+ */
+static void
+CleanupBackupHistory(void)
+{
+ DIR *xldir;
+ struct dirent *xlde;
+ char path[MAXPGPATH + sizeof(XLOGDIR)];
+
+ xldir = AllocateDir(XLOGDIR);
+
+ while ((xlde = ReadDir(xldir, XLOGDIR)) != NULL)
+ {
+ if (IsBackupHistoryFileName(xlde->d_name))
+ {
+ if (XLogArchiveCheckDone(xlde->d_name))
+ {
+ elog(DEBUG2, "removing WAL backup history file \"%s\"",
+ xlde->d_name);
+ snprintf(path, sizeof(path), XLOGDIR "/%s", xlde->d_name);
+ unlink(path);
+ XLogArchiveCleanup(xlde->d_name);
+ }
+ }
+ }
+
+ FreeDir(xldir);
+}
+
+/*
+ * I/O routines for pg_control
+ *
+ * *ControlFile is a buffer in shared memory that holds an image of the
+ * contents of pg_control. WriteControlFile() initializes pg_control
+ * given a preloaded buffer, ReadControlFile() loads the buffer from
+ * the pg_control file (during postmaster or standalone-backend startup),
+ * and UpdateControlFile() rewrites pg_control after we modify xlog state.
+ * InitControlFile() fills the buffer with initial values.
+ *
+ * For simplicity, WriteControlFile() initializes the fields of pg_control
+ * that are related to checking backend/database compatibility, and
+ * ReadControlFile() verifies they are correct. We could split out the
+ * I/O and compatibility-check functions, but there seems no need currently.
+ */
+
+static void
+InitControlFile(uint64 sysidentifier)
+{
+ char mock_auth_nonce[MOCK_AUTH_NONCE_LEN];
+
+ /*
+ * Generate a random nonce. This is used for authentication requests that
+ * will fail because the user does not exist. The nonce is used to create
+ * a genuine-looking password challenge for the non-existent user, in lieu
+ * of an actual stored password.
+ */
+ if (!pg_strong_random(mock_auth_nonce, MOCK_AUTH_NONCE_LEN))
+ ereport(PANIC,
+ (errcode(ERRCODE_INTERNAL_ERROR),
+ errmsg("could not generate secret authorization token")));
+
+ memset(ControlFile, 0, sizeof(ControlFileData));
+ /* Initialize pg_control status fields */
+ ControlFile->system_identifier = sysidentifier;
+ memcpy(ControlFile->mock_authentication_nonce, mock_auth_nonce, MOCK_AUTH_NONCE_LEN);
+ ControlFile->state = DB_SHUTDOWNED;
+ ControlFile->unloggedLSN = FirstNormalUnloggedLSN;
+
+ /* Set important parameter values for use when replaying WAL */
+ ControlFile->MaxConnections = MaxConnections;
+ ControlFile->max_worker_processes = max_worker_processes;
+ ControlFile->max_wal_senders = max_wal_senders;
+ ControlFile->max_prepared_xacts = max_prepared_xacts;
+ ControlFile->max_locks_per_xact = max_locks_per_xact;
+ ControlFile->wal_level = wal_level;
+ ControlFile->wal_log_hints = wal_log_hints;
+ ControlFile->track_commit_timestamp = track_commit_timestamp;
+ ControlFile->data_checksum_version = bootstrap_data_checksum_version;
+}
+
+static void
+WriteControlFile(void)
+{
+ int fd;
+ char buffer[PG_CONTROL_FILE_SIZE]; /* need not be aligned */
+
+ /*
+ * Ensure that the size of the pg_control data structure is sane. See the
+ * comments for these symbols in pg_control.h.
+ */
+ StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_MAX_SAFE_SIZE,
+ "pg_control is too large for atomic disk writes");
+ StaticAssertStmt(sizeof(ControlFileData) <= PG_CONTROL_FILE_SIZE,
+ "sizeof(ControlFileData) exceeds PG_CONTROL_FILE_SIZE");
+
+ /*
+ * Initialize version and compatibility-check fields
+ */
+ ControlFile->pg_control_version = PG_CONTROL_VERSION;
+ ControlFile->catalog_version_no = CATALOG_VERSION_NO;
+
+ ControlFile->maxAlign = MAXIMUM_ALIGNOF;
+ ControlFile->floatFormat = FLOATFORMAT_VALUE;
+
+ ControlFile->blcksz = BLCKSZ;
+ ControlFile->relseg_size = RELSEG_SIZE;
+ ControlFile->xlog_blcksz = XLOG_BLCKSZ;
+ ControlFile->xlog_seg_size = wal_segment_size;
+
+ ControlFile->nameDataLen = NAMEDATALEN;
+ ControlFile->indexMaxKeys = INDEX_MAX_KEYS;
+
+ ControlFile->toast_max_chunk_size = TOAST_MAX_CHUNK_SIZE;
+ ControlFile->loblksize = LOBLKSIZE;
+
+ ControlFile->float8ByVal = FLOAT8PASSBYVAL;
+
+ /* Contents are protected with a CRC */
+ INIT_CRC32C(ControlFile->crc);
+ COMP_CRC32C(ControlFile->crc,
+ (char *) ControlFile,
+ offsetof(ControlFileData, crc));
+ FIN_CRC32C(ControlFile->crc);
+
+ /*
+ * We write out PG_CONTROL_FILE_SIZE bytes into pg_control, zero-padding
+ * the excess over sizeof(ControlFileData). This reduces the odds of
+ * premature-EOF errors when reading pg_control. We'll still fail when we
+ * check the contents of the file, but hopefully with a more specific
+ * error than "couldn't read pg_control".
+ */
+ memset(buffer, 0, PG_CONTROL_FILE_SIZE);
+ memcpy(buffer, ControlFile, sizeof(ControlFileData));
+
+ fd = BasicOpenFile(XLOG_CONTROL_FILE,
+ O_RDWR | O_CREAT | O_EXCL | PG_BINARY);
+ if (fd < 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not create file \"%s\": %m",
+ XLOG_CONTROL_FILE)));
+
+ errno = 0;
+ pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_WRITE);
+ if (write(fd, buffer, PG_CONTROL_FILE_SIZE) != PG_CONTROL_FILE_SIZE)
+ {
+ /* if write didn't set errno, assume problem is no disk space */
+ if (errno == 0)
+ errno = ENOSPC;
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not write to file \"%s\": %m",
+ XLOG_CONTROL_FILE)));
+ }
+ pgstat_report_wait_end();
+
+ pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_SYNC);
+ if (pg_fsync(fd) != 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not fsync file \"%s\": %m",
+ XLOG_CONTROL_FILE)));
+ pgstat_report_wait_end();
+
+ if (close(fd) != 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not close file \"%s\": %m",
+ XLOG_CONTROL_FILE)));
+}
+
+static void
+ReadControlFile(void)
+{
+ pg_crc32c crc;
+ int fd;
+ static char wal_segsz_str[20];
+ int r;
+
+ /*
+ * Read data...
+ */
+ fd = BasicOpenFile(XLOG_CONTROL_FILE,
+ O_RDWR | PG_BINARY);
+ if (fd < 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not open file \"%s\": %m",
+ XLOG_CONTROL_FILE)));
+
+ pgstat_report_wait_start(WAIT_EVENT_CONTROL_FILE_READ);
+ r = read(fd, ControlFile, sizeof(ControlFileData));
+ if (r != sizeof(ControlFileData))
+ {
+ if (r < 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not read file \"%s\": %m",
+ XLOG_CONTROL_FILE)));
+ else
+ ereport(PANIC,
+ (errcode(ERRCODE_DATA_CORRUPTED),
+ errmsg("could not read file \"%s\": read %d of %zu",
+ XLOG_CONTROL_FILE, r, sizeof(ControlFileData))));
+ }
+ pgstat_report_wait_end();
+
+ close(fd);
+
+ /*
+ * Check for expected pg_control format version. If this is wrong, the
+ * CRC check will likely fail because we'll be checking the wrong number
+ * of bytes. Complaining about wrong version will probably be more
+ * enlightening than complaining about wrong CRC.
+ */
+
+ if (ControlFile->pg_control_version != PG_CONTROL_VERSION && ControlFile->pg_control_version % 65536 == 0 && ControlFile->pg_control_version / 65536 != 0)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with PG_CONTROL_VERSION %d (0x%08x),"
+ " but the server was compiled with PG_CONTROL_VERSION %d (0x%08x).",
+ ControlFile->pg_control_version, ControlFile->pg_control_version,
+ PG_CONTROL_VERSION, PG_CONTROL_VERSION),
+ errhint("This could be a problem of mismatched byte ordering. It looks like you need to initdb.")));
+
+ if (ControlFile->pg_control_version != PG_CONTROL_VERSION)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with PG_CONTROL_VERSION %d,"
+ " but the server was compiled with PG_CONTROL_VERSION %d.",
+ ControlFile->pg_control_version, PG_CONTROL_VERSION),
+ errhint("It looks like you need to initdb.")));
+
+ /* Now check the CRC. */
+ INIT_CRC32C(crc);
+ COMP_CRC32C(crc,
+ (char *) ControlFile,
+ offsetof(ControlFileData, crc));
+ FIN_CRC32C(crc);
+
+ if (!EQ_CRC32C(crc, ControlFile->crc))
+ ereport(FATAL,
+ (errmsg("incorrect checksum in control file")));
+
+ /*
+ * Do compatibility checking immediately. If the database isn't
+ * compatible with the backend executable, we want to abort before we can
+ * possibly do any damage.
+ */
+ if (ControlFile->catalog_version_no != CATALOG_VERSION_NO)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with CATALOG_VERSION_NO %d,"
+ " but the server was compiled with CATALOG_VERSION_NO %d.",
+ ControlFile->catalog_version_no, CATALOG_VERSION_NO),
+ errhint("It looks like you need to initdb.")));
+ if (ControlFile->maxAlign != MAXIMUM_ALIGNOF)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with MAXALIGN %d,"
+ " but the server was compiled with MAXALIGN %d.",
+ ControlFile->maxAlign, MAXIMUM_ALIGNOF),
+ errhint("It looks like you need to initdb.")));
+ if (ControlFile->floatFormat != FLOATFORMAT_VALUE)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster appears to use a different floating-point number format than the server executable."),
+ errhint("It looks like you need to initdb.")));
+ if (ControlFile->blcksz != BLCKSZ)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with BLCKSZ %d,"
+ " but the server was compiled with BLCKSZ %d.",
+ ControlFile->blcksz, BLCKSZ),
+ errhint("It looks like you need to recompile or initdb.")));
+ if (ControlFile->relseg_size != RELSEG_SIZE)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with RELSEG_SIZE %d,"
+ " but the server was compiled with RELSEG_SIZE %d.",
+ ControlFile->relseg_size, RELSEG_SIZE),
+ errhint("It looks like you need to recompile or initdb.")));
+ if (ControlFile->xlog_blcksz != XLOG_BLCKSZ)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with XLOG_BLCKSZ %d,"
+ " but the server was compiled with XLOG_BLCKSZ %d.",
+ ControlFile->xlog_blcksz, XLOG_BLCKSZ),
+ errhint("It looks like you need to recompile or initdb.")));
+ if (ControlFile->nameDataLen != NAMEDATALEN)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with NAMEDATALEN %d,"
+ " but the server was compiled with NAMEDATALEN %d.",
+ ControlFile->nameDataLen, NAMEDATALEN),
+ errhint("It looks like you need to recompile or initdb.")));
+ if (ControlFile->indexMaxKeys != INDEX_MAX_KEYS)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with INDEX_MAX_KEYS %d,"
+ " but the server was compiled with INDEX_MAX_KEYS %d.",
+ ControlFile->indexMaxKeys, INDEX_MAX_KEYS),
+ errhint("It looks like you need to recompile or initdb.")));
+ if (ControlFile->toast_max_chunk_size != TOAST_MAX_CHUNK_SIZE)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with TOAST_MAX_CHUNK_SIZE %d,"
+ " but the server was compiled with TOAST_MAX_CHUNK_SIZE %d.",
+ ControlFile->toast_max_chunk_size, (int) TOAST_MAX_CHUNK_SIZE),
+ errhint("It looks like you need to recompile or initdb.")));
+ if (ControlFile->loblksize != LOBLKSIZE)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with LOBLKSIZE %d,"
+ " but the server was compiled with LOBLKSIZE %d.",
+ ControlFile->loblksize, (int) LOBLKSIZE),
+ errhint("It looks like you need to recompile or initdb.")));
+
+#ifdef USE_FLOAT8_BYVAL
+ if (ControlFile->float8ByVal != true)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized without USE_FLOAT8_BYVAL"
+ " but the server was compiled with USE_FLOAT8_BYVAL."),
+ errhint("It looks like you need to recompile or initdb.")));
+#else
+ if (ControlFile->float8ByVal != false)
+ ereport(FATAL,
+ (errmsg("database files are incompatible with server"),
+ errdetail("The database cluster was initialized with USE_FLOAT8_BYVAL"
+ " but the server was compiled without USE_FLOAT8_BYVAL."),
+ errhint("It looks like you need to recompile or initdb.")));
+#endif
+
+ wal_segment_size = ControlFile->xlog_seg_size;
+
+ if (!IsValidWalSegSize(wal_segment_size))
+ ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg_plural("WAL segment size must be a power of two between 1 MB and 1 GB, but the control file specifies %d byte",
+ "WAL segment size must be a power of two between 1 MB and 1 GB, but the control file specifies %d bytes",
+ wal_segment_size,
+ wal_segment_size)));
+
+ snprintf(wal_segsz_str, sizeof(wal_segsz_str), "%d", wal_segment_size);
+ SetConfigOption("wal_segment_size", wal_segsz_str, PGC_INTERNAL,
+ PGC_S_DYNAMIC_DEFAULT);
+
+ /* check and update variables dependent on wal_segment_size */
+ if (ConvertToXSegs(min_wal_size_mb, wal_segment_size) < 2)
+ ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("\"min_wal_size\" must be at least twice \"wal_segment_size\"")));
+
+ if (ConvertToXSegs(max_wal_size_mb, wal_segment_size) < 2)
+ ereport(ERROR, (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("\"max_wal_size\" must be at least twice \"wal_segment_size\"")));
+
+ UsableBytesInSegment =
+ (wal_segment_size / XLOG_BLCKSZ * UsableBytesInPage) -
+ (SizeOfXLogLongPHD - SizeOfXLogShortPHD);
+
+ CalculateCheckpointSegments();
+
+ /* Make the initdb settings visible as GUC variables, too */
+ SetConfigOption("data_checksums", DataChecksumsEnabled() ? "yes" : "no",
+ PGC_INTERNAL, PGC_S_DYNAMIC_DEFAULT);
+}
+
+/*
+ * Utility wrapper to update the control file. Note that the control
+ * file gets flushed.
+ */
+static void
+UpdateControlFile(void)
+{
+ update_controlfile(DataDir, ControlFile, true);
+}
+
+/*
+ * Returns the unique system identifier from control file.
+ */
+uint64
+GetSystemIdentifier(void)
+{
+ Assert(ControlFile != NULL);
+ return ControlFile->system_identifier;
+}
+
+/*
+ * Returns the random nonce from control file.
+ */
+char *
+GetMockAuthenticationNonce(void)
+{
+ Assert(ControlFile != NULL);
+ return ControlFile->mock_authentication_nonce;
+}
+
+/*
+ * Are checksums enabled for data pages?
+ */
+bool
+DataChecksumsEnabled(void)
+{
+ Assert(ControlFile != NULL);
+ return (ControlFile->data_checksum_version > 0);
+}
+
+/*
+ * Returns a fake LSN for unlogged relations.
+ *
+ * Each call generates an LSN that is greater than any previous value
+ * returned. The current counter value is saved and restored across clean
+ * shutdowns, but like unlogged relations, does not survive a crash. This can
+ * be used in lieu of real LSN values returned by XLogInsert, if you need an
+ * LSN-like increasing sequence of numbers without writing any WAL.
+ */
+XLogRecPtr
+GetFakeLSNForUnloggedRel(void)
+{
+ XLogRecPtr nextUnloggedLSN;
+
+ /* increment the unloggedLSN counter, need SpinLock */
+ SpinLockAcquire(&XLogCtl->ulsn_lck);
+ nextUnloggedLSN = XLogCtl->unloggedLSN++;
+ SpinLockRelease(&XLogCtl->ulsn_lck);
+
+ return nextUnloggedLSN;
+}
+
+/*
+ * Auto-tune the number of XLOG buffers.
+ *
+ * The preferred setting for wal_buffers is about 3% of shared_buffers, with
+ * a maximum of one XLOG segment (there is little reason to think that more
+ * is helpful, at least so long as we force an fsync when switching log files)
+ * and a minimum of 8 blocks (which was the default value prior to PostgreSQL
+ * 9.1, when auto-tuning was added).
+ *
+ * This should not be called until NBuffers has received its final value.
+ */
+static int
+XLOGChooseNumBuffers(void)
+{
+ int xbuffers;
+
+ xbuffers = NBuffers / 32;
+ if (xbuffers > (wal_segment_size / XLOG_BLCKSZ))
+ xbuffers = (wal_segment_size / XLOG_BLCKSZ);
+ if (xbuffers < 8)
+ xbuffers = 8;
+ return xbuffers;
+}
+
+/*
+ * GUC check_hook for wal_buffers
+ */
+bool
+check_wal_buffers(int *newval, void **extra, GucSource source)
+{
+ /*
+ * -1 indicates a request for auto-tune.
+ */
+ if (*newval == -1)
+ {
+ /*
+ * If we haven't yet changed the boot_val default of -1, just let it
+ * be. We'll fix it when XLOGShmemSize is called.
+ */
+ if (XLOGbuffers == -1)
+ return true;
+
+ /* Otherwise, substitute the auto-tune value */
+ *newval = XLOGChooseNumBuffers();
+ }
+
+ /*
+ * We clamp manually-set values to at least 4 blocks. Prior to PostgreSQL
+ * 9.1, a minimum of 4 was enforced by guc.c, but since that is no longer
+ * the case, we just silently treat such values as a request for the
+ * minimum. (We could throw an error instead, but that doesn't seem very
+ * helpful.)
+ */
+ if (*newval < 4)
+ *newval = 4;
+
+ return true;
+}
+
+/*
+ * Read the control file, set respective GUCs.
+ *
+ * This is to be called during startup, including a crash recovery cycle,
+ * unless in bootstrap mode, where no control file yet exists. As there's no
+ * usable shared memory yet (its sizing can depend on the contents of the
+ * control file!), first store the contents in local memory. XLOGShmemInit()
+ * will then copy it to shared memory later.
+ *
+ * reset just controls whether previous contents are to be expected (in the
+ * reset case, there's a dangling pointer into old shared memory), or not.
+ */
+void
+LocalProcessControlFile(bool reset)
+{
+ Assert(reset || ControlFile == NULL);
+ ControlFile = palloc(sizeof(ControlFileData));
+ ReadControlFile();
+}
+
+/*
+ * Initialization of shared memory for XLOG
+ */
+Size
+XLOGShmemSize(void)
+{
+ Size size;
+
+ /*
+ * If the value of wal_buffers is -1, use the preferred auto-tune value.
+ * This isn't an amazingly clean place to do this, but we must wait till
+ * NBuffers has received its final value, and must do it before using the
+ * value of XLOGbuffers to do anything important.
+ *
+ * We prefer to report this value's source as PGC_S_DYNAMIC_DEFAULT.
+ * However, if the DBA explicitly set wal_buffers = -1 in the config file,
+ * then PGC_S_DYNAMIC_DEFAULT will fail to override that and we must force
+ * the matter with PGC_S_OVERRIDE.
+ */
+ if (XLOGbuffers == -1)
+ {
+ char buf[32];
+
+ snprintf(buf, sizeof(buf), "%d", XLOGChooseNumBuffers());
+ SetConfigOption("wal_buffers", buf, PGC_POSTMASTER,
+ PGC_S_DYNAMIC_DEFAULT);
+ if (XLOGbuffers == -1) /* failed to apply it? */
+ SetConfigOption("wal_buffers", buf, PGC_POSTMASTER,
+ PGC_S_OVERRIDE);
+ }
+ Assert(XLOGbuffers > 0);
+
+ /* XLogCtl */
+ size = sizeof(XLogCtlData);
+
+ /* WAL insertion locks, plus alignment */
+ size = add_size(size, mul_size(sizeof(WALInsertLockPadded), NUM_XLOGINSERT_LOCKS + 1));
+ /* xlblocks array */
+ size = add_size(size, mul_size(sizeof(XLogRecPtr), XLOGbuffers));
+ /* extra alignment padding for XLOG I/O buffers */
+ size = add_size(size, XLOG_BLCKSZ);
+ /* and the buffers themselves */
+ size = add_size(size, mul_size(XLOG_BLCKSZ, XLOGbuffers));
+
+ /*
+ * Note: we don't count ControlFileData, it comes out of the "slop factor"
+ * added by CreateSharedMemoryAndSemaphores. This lets us use this
+ * routine again below to compute the actual allocation size.
+ */
+
+ return size;
+}
+
+void
+XLOGShmemInit(void)
+{
+ bool foundCFile,
+ foundXLog;
+ char *allocptr;
+ int i;
+ ControlFileData *localControlFile;
+
+#ifdef WAL_DEBUG
+
+ /*
+ * Create a memory context for WAL debugging that's exempt from the normal
+ * "no pallocs in critical section" rule. Yes, that can lead to a PANIC if
+ * an allocation fails, but wal_debug is not for production use anyway.
+ */
+ if (walDebugCxt == NULL)
+ {
+ walDebugCxt = AllocSetContextCreate(TopMemoryContext,
+ "WAL Debug",
+ ALLOCSET_DEFAULT_SIZES);
+ MemoryContextAllowInCriticalSection(walDebugCxt, true);
+ }
+#endif
+
+
+ XLogCtl = (XLogCtlData *)
+ ShmemInitStruct("XLOG Ctl", XLOGShmemSize(), &foundXLog);
+
+ localControlFile = ControlFile;
+ ControlFile = (ControlFileData *)
+ ShmemInitStruct("Control File", sizeof(ControlFileData), &foundCFile);
+
+ if (foundCFile || foundXLog)
+ {
+ /* both should be present or neither */
+ Assert(foundCFile && foundXLog);
+
+ /* Initialize local copy of WALInsertLocks */
+ WALInsertLocks = XLogCtl->Insert.WALInsertLocks;
+
+ if (localControlFile)
+ pfree(localControlFile);
+ return;
+ }
+ memset(XLogCtl, 0, sizeof(XLogCtlData));
+
+ /*
+ * Already have read control file locally, unless in bootstrap mode. Move
+ * contents into shared memory.
+ */
+ if (localControlFile)
+ {
+ memcpy(ControlFile, localControlFile, sizeof(ControlFileData));
+ pfree(localControlFile);
+ }
+
+ /*
+ * Since XLogCtlData contains XLogRecPtr fields, its sizeof should be a
+ * multiple of the alignment for same, so no extra alignment padding is
+ * needed here.
+ */
+ allocptr = ((char *) XLogCtl) + sizeof(XLogCtlData);
+ XLogCtl->xlblocks = (XLogRecPtr *) allocptr;
+ memset(XLogCtl->xlblocks, 0, sizeof(XLogRecPtr) * XLOGbuffers);
+ allocptr += sizeof(XLogRecPtr) * XLOGbuffers;
+
+
+ /* WAL insertion locks. Ensure they're aligned to the full padded size */
+ allocptr += sizeof(WALInsertLockPadded) -
+ ((uintptr_t) allocptr) % sizeof(WALInsertLockPadded);
+ WALInsertLocks = XLogCtl->Insert.WALInsertLocks =
+ (WALInsertLockPadded *) allocptr;
+ allocptr += sizeof(WALInsertLockPadded) * NUM_XLOGINSERT_LOCKS;
+
+ for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++)
+ {
+ LWLockInitialize(&WALInsertLocks[i].l.lock, LWTRANCHE_WAL_INSERT);
+ WALInsertLocks[i].l.insertingAt = InvalidXLogRecPtr;
+ WALInsertLocks[i].l.lastImportantAt = InvalidXLogRecPtr;
+ }
+
+ /*
+ * Align the start of the page buffers to a full xlog block size boundary.
+ * This simplifies some calculations in XLOG insertion. It is also
+ * required for O_DIRECT.
+ */
+ allocptr = (char *) TYPEALIGN(XLOG_BLCKSZ, allocptr);
+ XLogCtl->pages = allocptr;
+ memset(XLogCtl->pages, 0, (Size) XLOG_BLCKSZ * XLOGbuffers);
+
+ /*
+ * Do basic initialization of XLogCtl shared data. (StartupXLOG will fill
+ * in additional info.)
+ */
+ XLogCtl->XLogCacheBlck = XLOGbuffers - 1;
+ XLogCtl->SharedRecoveryState = RECOVERY_STATE_CRASH;
+ XLogCtl->InstallXLogFileSegmentActive = false;
+ XLogCtl->WalWriterSleeping = false;
+
+ SpinLockInit(&XLogCtl->Insert.insertpos_lck);
+ SpinLockInit(&XLogCtl->info_lck);
+ SpinLockInit(&XLogCtl->ulsn_lck);
+}
+
+/*
+ * This func must be called ONCE on system install. It creates pg_control
+ * and the initial XLOG segment.
+ */
+void
+BootStrapXLOG(void)
+{
+ CheckPoint checkPoint;
+ char *buffer;
+ XLogPageHeader page;
+ XLogLongPageHeader longpage;
+ XLogRecord *record;
+ char *recptr;
+ uint64 sysidentifier;
+ struct timeval tv;
+ pg_crc32c crc;
+
+ /* allow ordinary WAL segment creation, like StartupXLOG() would */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ XLogCtl->InstallXLogFileSegmentActive = true;
+ LWLockRelease(ControlFileLock);
+
+ /*
+ * Select a hopefully-unique system identifier code for this installation.
+ * We use the result of gettimeofday(), including the fractional seconds
+ * field, as being about as unique as we can easily get. (Think not to
+ * use random(), since it hasn't been seeded and there's no portable way
+ * to seed it other than the system clock value...) The upper half of the
+ * uint64 value is just the tv_sec part, while the lower half contains the
+ * tv_usec part (which must fit in 20 bits), plus 12 bits from our current
+ * PID for a little extra uniqueness. A person knowing this encoding can
+ * determine the initialization time of the installation, which could
+ * perhaps be useful sometimes.
+ */
+ gettimeofday(&tv, NULL);
+ sysidentifier = ((uint64) tv.tv_sec) << 32;
+ sysidentifier |= ((uint64) tv.tv_usec) << 12;
+ sysidentifier |= getpid() & 0xFFF;
+
+ /* page buffer must be aligned suitably for O_DIRECT */
+ buffer = (char *) palloc(XLOG_BLCKSZ + XLOG_BLCKSZ);
+ page = (XLogPageHeader) TYPEALIGN(XLOG_BLCKSZ, buffer);
+ memset(page, 0, XLOG_BLCKSZ);
+
+ /*
+ * Set up information for the initial checkpoint record
+ *
+ * The initial checkpoint record is written to the beginning of the WAL
+ * segment with logid=0 logseg=1. The very first WAL segment, 0/0, is not
+ * used, so that we can use 0/0 to mean "before any valid WAL segment".
+ */
+ checkPoint.redo = wal_segment_size + SizeOfXLogLongPHD;
+ checkPoint.ThisTimeLineID = BootstrapTimeLineID;
+ checkPoint.PrevTimeLineID = BootstrapTimeLineID;
+ checkPoint.fullPageWrites = fullPageWrites;
+ checkPoint.nextXid =
+ FullTransactionIdFromEpochAndXid(0, FirstNormalTransactionId);
+ checkPoint.nextOid = FirstGenbkiObjectId;
+ checkPoint.nextMulti = FirstMultiXactId;
+ checkPoint.nextMultiOffset = 0;
+ checkPoint.oldestXid = FirstNormalTransactionId;
+ checkPoint.oldestXidDB = Template1DbOid;
+ checkPoint.oldestMulti = FirstMultiXactId;
+ checkPoint.oldestMultiDB = Template1DbOid;
+ checkPoint.oldestCommitTsXid = InvalidTransactionId;
+ checkPoint.newestCommitTsXid = InvalidTransactionId;
+ checkPoint.time = (pg_time_t) time(NULL);
+ checkPoint.oldestActiveXid = InvalidTransactionId;
+
+ ShmemVariableCache->nextXid = checkPoint.nextXid;
+ ShmemVariableCache->nextOid = checkPoint.nextOid;
+ ShmemVariableCache->oidCount = 0;
+ MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset);
+ AdvanceOldestClogXid(checkPoint.oldestXid);
+ SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB);
+ SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true);
+ SetCommitTsLimit(InvalidTransactionId, InvalidTransactionId);
+
+ /* Set up the XLOG page header */
+ page->xlp_magic = XLOG_PAGE_MAGIC;
+ page->xlp_info = XLP_LONG_HEADER;
+ page->xlp_tli = BootstrapTimeLineID;
+ page->xlp_pageaddr = wal_segment_size;
+ longpage = (XLogLongPageHeader) page;
+ longpage->xlp_sysid = sysidentifier;
+ longpage->xlp_seg_size = wal_segment_size;
+ longpage->xlp_xlog_blcksz = XLOG_BLCKSZ;
+
+ /* Insert the initial checkpoint record */
+ recptr = ((char *) page + SizeOfXLogLongPHD);
+ record = (XLogRecord *) recptr;
+ record->xl_prev = 0;
+ record->xl_xid = InvalidTransactionId;
+ record->xl_tot_len = SizeOfXLogRecord + SizeOfXLogRecordDataHeaderShort + sizeof(checkPoint);
+ record->xl_info = XLOG_CHECKPOINT_SHUTDOWN;
+ record->xl_rmid = RM_XLOG_ID;
+ recptr += SizeOfXLogRecord;
+ /* fill the XLogRecordDataHeaderShort struct */
+ *(recptr++) = (char) XLR_BLOCK_ID_DATA_SHORT;
+ *(recptr++) = sizeof(checkPoint);
+ memcpy(recptr, &checkPoint, sizeof(checkPoint));
+ recptr += sizeof(checkPoint);
+ Assert(recptr - (char *) record == record->xl_tot_len);
+
+ INIT_CRC32C(crc);
+ COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord);
+ COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc));
+ FIN_CRC32C(crc);
+ record->xl_crc = crc;
+
+ /* Create first XLOG segment file */
+ openLogTLI = BootstrapTimeLineID;
+ openLogFile = XLogFileInit(1, BootstrapTimeLineID);
+
+ /*
+ * We needn't bother with Reserve/ReleaseExternalFD here, since we'll
+ * close the file again in a moment.
+ */
+
+ /* Write the first page with the initial record */
+ errno = 0;
+ pgstat_report_wait_start(WAIT_EVENT_WAL_BOOTSTRAP_WRITE);
+ if (write(openLogFile, page, XLOG_BLCKSZ) != XLOG_BLCKSZ)
+ {
+ /* if write didn't set errno, assume problem is no disk space */
+ if (errno == 0)
+ errno = ENOSPC;
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not write bootstrap write-ahead log file: %m")));
+ }
+ pgstat_report_wait_end();
+
+ pgstat_report_wait_start(WAIT_EVENT_WAL_BOOTSTRAP_SYNC);
+ if (pg_fsync(openLogFile) != 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not fsync bootstrap write-ahead log file: %m")));
+ pgstat_report_wait_end();
+
+ if (close(openLogFile) != 0)
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not close bootstrap write-ahead log file: %m")));
+
+ openLogFile = -1;
+
+ /* Now create pg_control */
+ InitControlFile(sysidentifier);
+ ControlFile->time = checkPoint.time;
+ ControlFile->checkPoint = checkPoint.redo;
+ ControlFile->checkPointCopy = checkPoint;
+
+ /* some additional ControlFile fields are set in WriteControlFile() */
+ WriteControlFile();
+
+ /* Bootstrap the commit log, too */
+ BootStrapCLOG();
+ BootStrapCommitTs();
+ BootStrapSUBTRANS();
+ BootStrapMultiXact();
+
+ pfree(buffer);
+
+ /*
+ * Force control file to be read - in contrast to normal processing we'd
+ * otherwise never run the checks and GUC related initializations therein.
+ */
+ ReadControlFile();
+}
+
+static char *
+str_time(pg_time_t tnow)
+{
+ static char buf[128];
+
+ pg_strftime(buf, sizeof(buf),
+ "%Y-%m-%d %H:%M:%S %Z",
+ pg_localtime(&tnow, log_timezone));
+
+ return buf;
+}
+
+/*
+ * Initialize the first WAL segment on new timeline.
+ */
+static void
+XLogInitNewTimeline(TimeLineID endTLI, XLogRecPtr endOfLog, TimeLineID newTLI)
+{
+ char xlogfname[MAXFNAMELEN];
+ XLogSegNo endLogSegNo;
+ XLogSegNo startLogSegNo;
+
+ /* we always switch to a new timeline after archive recovery */
+ Assert(endTLI != newTLI);
+
+ /*
+ * Update min recovery point one last time.
+ */
+ UpdateMinRecoveryPoint(InvalidXLogRecPtr, true);
+
+ /*
+ * Calculate the last segment on the old timeline, and the first segment
+ * on the new timeline. If the switch happens in the middle of a segment,
+ * they are the same, but if the switch happens exactly at a segment
+ * boundary, startLogSegNo will be endLogSegNo + 1.
+ */
+ XLByteToPrevSeg(endOfLog, endLogSegNo, wal_segment_size);
+ XLByteToSeg(endOfLog, startLogSegNo, wal_segment_size);
+
+ /*
+ * Initialize the starting WAL segment for the new timeline. If the switch
+ * happens in the middle of a segment, copy data from the last WAL segment
+ * of the old timeline up to the switch point, to the starting WAL segment
+ * on the new timeline.
+ */
+ if (endLogSegNo == startLogSegNo)
+ {
+ /*
+ * Make a copy of the file on the new timeline.
+ *
+ * Writing WAL isn't allowed yet, so there are no locking
+ * considerations. But we should be just as tense as XLogFileInit to
+ * avoid emplacing a bogus file.
+ */
+ XLogFileCopy(newTLI, endLogSegNo, endTLI, endLogSegNo,
+ XLogSegmentOffset(endOfLog, wal_segment_size));
+ }
+ else
+ {
+ /*
+ * The switch happened at a segment boundary, so just create the next
+ * segment on the new timeline.
+ */
+ int fd;
+
+ fd = XLogFileInit(startLogSegNo, newTLI);
+
+ if (close(fd) != 0)
+ {
+ char xlogfname[MAXFNAMELEN];
+ int save_errno = errno;
+
+ XLogFileName(xlogfname, newTLI, startLogSegNo, wal_segment_size);
+ errno = save_errno;
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not close file \"%s\": %m", xlogfname)));
+ }
+ }
+
+ /*
+ * Let's just make real sure there are not .ready or .done flags posted
+ * for the new segment.
+ */
+ XLogFileName(xlogfname, newTLI, startLogSegNo, wal_segment_size);
+ XLogArchiveCleanup(xlogfname);
+}
+
+/*
+ * Perform cleanup actions at the conclusion of archive recovery.
+ */
+static void
+CleanupAfterArchiveRecovery(TimeLineID EndOfLogTLI, XLogRecPtr EndOfLog,
+ TimeLineID newTLI)
+{
+ /*
+ * Execute the recovery_end_command, if any.
+ */
+ if (recoveryEndCommand && strcmp(recoveryEndCommand, "") != 0)
+ ExecuteRecoveryCommand(recoveryEndCommand,
+ "recovery_end_command",
+ true,
+ WAIT_EVENT_RECOVERY_END_COMMAND);
+
+ /*
+ * We switched to a new timeline. Clean up segments on the old timeline.
+ *
+ * If there are any higher-numbered segments on the old timeline, remove
+ * them. They might contain valid WAL, but they might also be
+ * pre-allocated files containing garbage. In any case, they are not part
+ * of the new timeline's history so we don't need them.
+ */
+ RemoveNonParentXlogFiles(EndOfLog, newTLI);
+
+ /*
+ * If the switch happened in the middle of a segment, what to do with the
+ * last, partial segment on the old timeline? If we don't archive it, and
+ * the server that created the WAL never archives it either (e.g. because
+ * it was hit by a meteor), it will never make it to the archive. That's
+ * OK from our point of view, because the new segment that we created with
+ * the new TLI contains all the WAL from the old timeline up to the switch
+ * point. But if you later try to do PITR to the "missing" WAL on the old
+ * timeline, recovery won't find it in the archive. It's physically
+ * present in the new file with new TLI, but recovery won't look there
+ * when it's recovering to the older timeline. On the other hand, if we
+ * archive the partial segment, and the original server on that timeline
+ * is still running and archives the completed version of the same segment
+ * later, it will fail. (We used to do that in 9.4 and below, and it
+ * caused such problems).
+ *
+ * As a compromise, we rename the last segment with the .partial suffix,
+ * and archive it. Archive recovery will never try to read .partial
+ * segments, so they will normally go unused. But in the odd PITR case,
+ * the administrator can copy them manually to the pg_wal directory
+ * (removing the suffix). They can be useful in debugging, too.
+ *
+ * If a .done or .ready file already exists for the old timeline, however,
+ * we had already determined that the segment is complete, so we can let
+ * it be archived normally. (In particular, if it was restored from the
+ * archive to begin with, it's expected to have a .done file).
+ */
+ if (XLogSegmentOffset(EndOfLog, wal_segment_size) != 0 &&
+ XLogArchivingActive())
+ {
+ char origfname[MAXFNAMELEN];
+ XLogSegNo endLogSegNo;
+
+ XLByteToPrevSeg(EndOfLog, endLogSegNo, wal_segment_size);
+ XLogFileName(origfname, EndOfLogTLI, endLogSegNo, wal_segment_size);
+
+ if (!XLogArchiveIsReadyOrDone(origfname))
+ {
+ char origpath[MAXPGPATH];
+ char partialfname[MAXFNAMELEN];
+ char partialpath[MAXPGPATH];
+
+ XLogFilePath(origpath, EndOfLogTLI, endLogSegNo, wal_segment_size);
+ snprintf(partialfname, MAXFNAMELEN, "%s.partial", origfname);
+ snprintf(partialpath, MAXPGPATH, "%s.partial", origpath);
+
+ /*
+ * Make sure there's no .done or .ready file for the .partial
+ * file.
+ */
+ XLogArchiveCleanup(partialfname);
+
+ durable_rename(origpath, partialpath, ERROR);
+ XLogArchiveNotify(partialfname);
+ }
+ }
+}
+
+/*
+ * Check to see if required parameters are set high enough on this server
+ * for various aspects of recovery operation.
+ *
+ * Note that all the parameters which this function tests need to be
+ * listed in Administrator's Overview section in high-availability.sgml.
+ * If you change them, don't forget to update the list.
+ */
+static void
+CheckRequiredParameterValues(void)
+{
+ /*
+ * For archive recovery, the WAL must be generated with at least 'replica'
+ * wal_level.
+ */
+ if (ArchiveRecoveryRequested && ControlFile->wal_level == WAL_LEVEL_MINIMAL)
+ {
+ ereport(FATAL,
+ (errmsg("WAL was generated with wal_level=minimal, cannot continue recovering"),
+ errdetail("This happens if you temporarily set wal_level=minimal on the server."),
+ errhint("Use a backup taken after setting wal_level to higher than minimal.")));
+ }
+
+ /*
+ * For Hot Standby, the WAL must be generated with 'replica' mode, and we
+ * must have at least as many backend slots as the primary.
+ */
+ if (ArchiveRecoveryRequested && EnableHotStandby)
+ {
+ /* We ignore autovacuum_max_workers when we make this test. */
+ RecoveryRequiresIntParameter("max_connections",
+ MaxConnections,
+ ControlFile->MaxConnections);
+ RecoveryRequiresIntParameter("max_worker_processes",
+ max_worker_processes,
+ ControlFile->max_worker_processes);
+ RecoveryRequiresIntParameter("max_wal_senders",
+ max_wal_senders,
+ ControlFile->max_wal_senders);
+ RecoveryRequiresIntParameter("max_prepared_transactions",
+ max_prepared_xacts,
+ ControlFile->max_prepared_xacts);
+ RecoveryRequiresIntParameter("max_locks_per_transaction",
+ max_locks_per_xact,
+ ControlFile->max_locks_per_xact);
+ }
+}
+
+/*
+ * This must be called ONCE during postmaster or standalone-backend startup
+ */
+void
+StartupXLOG(void)
+{
+ XLogCtlInsert *Insert;
+ CheckPoint checkPoint;
+ bool wasShutdown;
+ bool didCrash;
+ bool haveTblspcMap;
+ bool haveBackupLabel;
+ XLogRecPtr EndOfLog;
+ TimeLineID EndOfLogTLI;
+ TimeLineID newTLI;
+ bool performedWalRecovery;
+ EndOfWalRecoveryInfo *endOfRecoveryInfo;
+ XLogRecPtr abortedRecPtr;
+ XLogRecPtr missingContrecPtr;
+ TransactionId oldestActiveXID;
+ bool promoted = false;
+
+ /*
+ * We should have an aux process resource owner to use, and we should not
+ * be in a transaction that's installed some other resowner.
+ */
+ Assert(AuxProcessResourceOwner != NULL);
+ Assert(CurrentResourceOwner == NULL ||
+ CurrentResourceOwner == AuxProcessResourceOwner);
+ CurrentResourceOwner = AuxProcessResourceOwner;
+
+ /*
+ * Check that contents look valid.
+ */
+ if (!XRecOffIsValid(ControlFile->checkPoint))
+ ereport(FATAL,
+ (errmsg("control file contains invalid checkpoint location")));
+
+ switch (ControlFile->state)
+ {
+ case DB_SHUTDOWNED:
+
+ /*
+ * This is the expected case, so don't be chatty in standalone
+ * mode
+ */
+ ereport(IsPostmasterEnvironment ? LOG : NOTICE,
+ (errmsg("database system was shut down at %s",
+ str_time(ControlFile->time))));
+ break;
+
+ case DB_SHUTDOWNED_IN_RECOVERY:
+ ereport(LOG,
+ (errmsg("database system was shut down in recovery at %s",
+ str_time(ControlFile->time))));
+ break;
+
+ case DB_SHUTDOWNING:
+ ereport(LOG,
+ (errmsg("database system shutdown was interrupted; last known up at %s",
+ str_time(ControlFile->time))));
+ break;
+
+ case DB_IN_CRASH_RECOVERY:
+ ereport(LOG,
+ (errmsg("database system was interrupted while in recovery at %s",
+ str_time(ControlFile->time)),
+ errhint("This probably means that some data is corrupted and"
+ " you will have to use the last backup for recovery.")));
+ break;
+
+ case DB_IN_ARCHIVE_RECOVERY:
+ ereport(LOG,
+ (errmsg("database system was interrupted while in recovery at log time %s",
+ str_time(ControlFile->checkPointCopy.time)),
+ errhint("If this has occurred more than once some data might be corrupted"
+ " and you might need to choose an earlier recovery target.")));
+ break;
+
+ case DB_IN_PRODUCTION:
+ ereport(LOG,
+ (errmsg("database system was interrupted; last known up at %s",
+ str_time(ControlFile->time))));
+ break;
+
+ default:
+ ereport(FATAL,
+ (errmsg("control file contains invalid database cluster state")));
+ }
+
+ /* This is just to allow attaching to startup process with a debugger */
+#ifdef XLOG_REPLAY_DELAY
+ if (ControlFile->state != DB_SHUTDOWNED)
+ pg_usleep(60000000L);
+#endif
+
+ /*
+ * Verify that pg_wal and pg_wal/archive_status exist. In cases where
+ * someone has performed a copy for PITR, these directories may have been
+ * excluded and need to be re-created.
+ */
+ ValidateXLOGDirectoryStructure();
+
+ /* Set up timeout handler needed to report startup progress. */
+ if (!IsBootstrapProcessingMode())
+ RegisterTimeout(STARTUP_PROGRESS_TIMEOUT,
+ startup_progress_timeout_handler);
+
+ /*----------
+ * If we previously crashed, perform a couple of actions:
+ *
+ * - The pg_wal directory may still include some temporary WAL segments
+ * used when creating a new segment, so perform some clean up to not
+ * bloat this path. This is done first as there is no point to sync
+ * this temporary data.
+ *
+ * - There might be data which we had written, intending to fsync it, but
+ * which we had not actually fsync'd yet. Therefore, a power failure in
+ * the near future might cause earlier unflushed writes to be lost, even
+ * though more recent data written to disk from here on would be
+ * persisted. To avoid that, fsync the entire data directory.
+ */
+ if (ControlFile->state != DB_SHUTDOWNED &&
+ ControlFile->state != DB_SHUTDOWNED_IN_RECOVERY)
+ {
+ RemoveTempXlogFiles();
+ SyncDataDirectory();
+ didCrash = true;
+ }
+ else
+ didCrash = false;
+
+ /*
+ * Prepare for WAL recovery if needed.
+ *
+ * InitWalRecovery analyzes the control file and the backup label file, if
+ * any. It updates the in-memory ControlFile buffer according to the
+ * starting checkpoint, and sets InRecovery and ArchiveRecoveryRequested.
+ * It also applies the tablespace map file, if any.
+ */
+ InitWalRecovery(ControlFile, &wasShutdown,
+ &haveBackupLabel, &haveTblspcMap);
+ checkPoint = ControlFile->checkPointCopy;
+
+ /* initialize shared memory variables from the checkpoint record */
+ ShmemVariableCache->nextXid = checkPoint.nextXid;
+ ShmemVariableCache->nextOid = checkPoint.nextOid;
+ ShmemVariableCache->oidCount = 0;
+ MultiXactSetNextMXact(checkPoint.nextMulti, checkPoint.nextMultiOffset);
+ AdvanceOldestClogXid(checkPoint.oldestXid);
+ SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB);
+ SetMultiXactIdLimit(checkPoint.oldestMulti, checkPoint.oldestMultiDB, true);
+ SetCommitTsLimit(checkPoint.oldestCommitTsXid,
+ checkPoint.newestCommitTsXid);
+ XLogCtl->ckptFullXid = checkPoint.nextXid;
+
+ /*
+ * Clear out any old relcache cache files. This is *necessary* if we do
+ * any WAL replay, since that would probably result in the cache files
+ * being out of sync with database reality. In theory we could leave them
+ * in place if the database had been cleanly shut down, but it seems
+ * safest to just remove them always and let them be rebuilt during the
+ * first backend startup. These files needs to be removed from all
+ * directories including pg_tblspc, however the symlinks are created only
+ * after reading tablespace_map file in case of archive recovery from
+ * backup, so needs to clear old relcache files here after creating
+ * symlinks.
+ */
+ RelationCacheInitFileRemove();
+
+ /*
+ * Initialize replication slots, before there's a chance to remove
+ * required resources.
+ */
+ StartupReplicationSlots();
+
+ /*
+ * Startup logical state, needs to be setup now so we have proper data
+ * during crash recovery.
+ */
+ StartupReorderBuffer();
+
+ /*
+ * Startup CLOG. This must be done after ShmemVariableCache->nextXid has
+ * been initialized and before we accept connections or begin WAL replay.
+ */
+ StartupCLOG();
+
+ /*
+ * Startup MultiXact. We need to do this early to be able to replay
+ * truncations.
+ */
+ StartupMultiXact();
+
+ /*
+ * Ditto for commit timestamps. Activate the facility if the setting is
+ * enabled in the control file, as there should be no tracking of commit
+ * timestamps done when the setting was disabled. This facility can be
+ * started or stopped when replaying a XLOG_PARAMETER_CHANGE record.
+ */
+ if (ControlFile->track_commit_timestamp)
+ StartupCommitTs();
+
+ /*
+ * Recover knowledge about replay progress of known replication partners.
+ */
+ StartupReplicationOrigin();
+
+ /*
+ * Initialize unlogged LSN. On a clean shutdown, it's restored from the
+ * control file. On recovery, all unlogged relations are blown away, so
+ * the unlogged LSN counter can be reset too.
+ */
+ if (ControlFile->state == DB_SHUTDOWNED)
+ XLogCtl->unloggedLSN = ControlFile->unloggedLSN;
+ else
+ XLogCtl->unloggedLSN = FirstNormalUnloggedLSN;
+
+ /*
+ * Copy any missing timeline history files between 'now' and the recovery
+ * target timeline from archive to pg_wal. While we don't need those files
+ * ourselves - the history file of the recovery target timeline covers all
+ * the previous timelines in the history too - a cascading standby server
+ * might be interested in them. Or, if you archive the WAL from this
+ * server to a different archive than the primary, it'd be good for all
+ * the history files to get archived there after failover, so that you can
+ * use one of the old timelines as a PITR target. Timeline history files
+ * are small, so it's better to copy them unnecessarily than not copy them
+ * and regret later.
+ */
+ restoreTimeLineHistoryFiles(checkPoint.ThisTimeLineID, recoveryTargetTLI);
+
+ /*
+ * Before running in recovery, scan pg_twophase and fill in its status to
+ * be able to work on entries generated by redo. Doing a scan before
+ * taking any recovery action has the merit to discard any 2PC files that
+ * are newer than the first record to replay, saving from any conflicts at
+ * replay. This avoids as well any subsequent scans when doing recovery
+ * of the on-disk two-phase data.
+ */
+ restoreTwoPhaseData();
+
+ /*
+ * When starting with crash recovery, reset pgstat data - it might not be
+ * valid. Otherwise restore pgstat data. It's safe to do this here,
+ * because postmaster will not yet have started any other processes.
+ *
+ * NB: Restoring replication slot stats relies on slot state to have
+ * already been restored from disk.
+ *
+ * TODO: With a bit of extra work we could just start with a pgstat file
+ * associated with the checkpoint redo location we're starting from.
+ */
+ if (didCrash)
+ pgstat_discard_stats();
+ else
+ pgstat_restore_stats();
+
+ lastFullPageWrites = checkPoint.fullPageWrites;
+
+ RedoRecPtr = XLogCtl->RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo;
+ doPageWrites = lastFullPageWrites;
+
+ /* REDO */
+ if (InRecovery)
+ {
+ /* Initialize state for RecoveryInProgress() */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ if (InArchiveRecovery)
+ XLogCtl->SharedRecoveryState = RECOVERY_STATE_ARCHIVE;
+ else
+ XLogCtl->SharedRecoveryState = RECOVERY_STATE_CRASH;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * Update pg_control to show that we are recovering and to show the
+ * selected checkpoint as the place we are starting from. We also mark
+ * pg_control with any minimum recovery stop point obtained from a
+ * backup history file.
+ *
+ * No need to hold ControlFileLock yet, we aren't up far enough.
+ */
+ UpdateControlFile();
+
+ /*
+ * If there was a backup label file, it's done its job and the info
+ * has now been propagated into pg_control. We must get rid of the
+ * label file so that if we crash during recovery, we'll pick up at
+ * the latest recovery restartpoint instead of going all the way back
+ * to the backup start point. It seems prudent though to just rename
+ * the file out of the way rather than delete it completely.
+ */
+ if (haveBackupLabel)
+ {
+ unlink(BACKUP_LABEL_OLD);
+ durable_rename(BACKUP_LABEL_FILE, BACKUP_LABEL_OLD, FATAL);
+ }
+
+ /*
+ * If there was a tablespace_map file, it's done its job and the
+ * symlinks have been created. We must get rid of the map file so
+ * that if we crash during recovery, we don't create symlinks again.
+ * It seems prudent though to just rename the file out of the way
+ * rather than delete it completely.
+ */
+ if (haveTblspcMap)
+ {
+ unlink(TABLESPACE_MAP_OLD);
+ durable_rename(TABLESPACE_MAP, TABLESPACE_MAP_OLD, FATAL);
+ }
+
+ /*
+ * Initialize our local copy of minRecoveryPoint. When doing crash
+ * recovery we want to replay up to the end of WAL. Particularly, in
+ * the case of a promoted standby minRecoveryPoint value in the
+ * control file is only updated after the first checkpoint. However,
+ * if the instance crashes before the first post-recovery checkpoint
+ * is completed then recovery will use a stale location causing the
+ * startup process to think that there are still invalid page
+ * references when checking for data consistency.
+ */
+ if (InArchiveRecovery)
+ {
+ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint;
+ LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
+ }
+ else
+ {
+ LocalMinRecoveryPoint = InvalidXLogRecPtr;
+ LocalMinRecoveryPointTLI = 0;
+ }
+
+ /* Check that the GUCs used to generate the WAL allow recovery */
+ CheckRequiredParameterValues();
+
+ /*
+ * We're in recovery, so unlogged relations may be trashed and must be
+ * reset. This should be done BEFORE allowing Hot Standby
+ * connections, so that read-only backends don't try to read whatever
+ * garbage is left over from before.
+ */
+ ResetUnloggedRelations(UNLOGGED_RELATION_CLEANUP);
+
+ /*
+ * Likewise, delete any saved transaction snapshot files that got left
+ * behind by crashed backends.
+ */
+ DeleteAllExportedSnapshotFiles();
+
+ /*
+ * Initialize for Hot Standby, if enabled. We won't let backends in
+ * yet, not until we've reached the min recovery point specified in
+ * control file and we've established a recovery snapshot from a
+ * running-xacts WAL record.
+ */
+ if (ArchiveRecoveryRequested && EnableHotStandby)
+ {
+ TransactionId *xids;
+ int nxids;
+
+ ereport(DEBUG1,
+ (errmsg_internal("initializing for hot standby")));
+
+ InitRecoveryTransactionEnvironment();
+
+ if (wasShutdown)
+ oldestActiveXID = PrescanPreparedTransactions(&xids, &nxids);
+ else
+ oldestActiveXID = checkPoint.oldestActiveXid;
+ Assert(TransactionIdIsValid(oldestActiveXID));
+
+ /* Tell procarray about the range of xids it has to deal with */
+ ProcArrayInitRecovery(XidFromFullTransactionId(ShmemVariableCache->nextXid));
+
+ /*
+ * Startup subtrans only. CLOG, MultiXact and commit timestamp
+ * have already been started up and other SLRUs are not maintained
+ * during recovery and need not be started yet.
+ */
+ StartupSUBTRANS(oldestActiveXID);
+
+ /*
+ * If we're beginning at a shutdown checkpoint, we know that
+ * nothing was running on the primary at this point. So fake-up an
+ * empty running-xacts record and use that here and now. Recover
+ * additional standby state for prepared transactions.
+ */
+ if (wasShutdown)
+ {
+ RunningTransactionsData running;
+ TransactionId latestCompletedXid;
+
+ /*
+ * Construct a RunningTransactions snapshot representing a
+ * shut down server, with only prepared transactions still
+ * alive. We're never overflowed at this point because all
+ * subxids are listed with their parent prepared transactions.
+ */
+ running.xcnt = nxids;
+ running.subxcnt = 0;
+ running.subxid_overflow = false;
+ running.nextXid = XidFromFullTransactionId(checkPoint.nextXid);
+ running.oldestRunningXid = oldestActiveXID;
+ latestCompletedXid = XidFromFullTransactionId(checkPoint.nextXid);
+ TransactionIdRetreat(latestCompletedXid);
+ Assert(TransactionIdIsNormal(latestCompletedXid));
+ running.latestCompletedXid = latestCompletedXid;
+ running.xids = xids;
+
+ ProcArrayApplyRecoveryInfo(&running);
+
+ StandbyRecoverPreparedTransactions();
+ }
+ }
+
+ /*
+ * We're all set for replaying the WAL now. Do it.
+ */
+ PerformWalRecovery();
+ performedWalRecovery = true;
+ }
+ else
+ performedWalRecovery = false;
+
+ /*
+ * Finish WAL recovery.
+ */
+ endOfRecoveryInfo = FinishWalRecovery();
+ EndOfLog = endOfRecoveryInfo->endOfLog;
+ EndOfLogTLI = endOfRecoveryInfo->endOfLogTLI;
+ abortedRecPtr = endOfRecoveryInfo->abortedRecPtr;
+ missingContrecPtr = endOfRecoveryInfo->missingContrecPtr;
+
+ /*
+ * Reset ps status display, so as no information related to recovery
+ * shows up.
+ */
+ set_ps_display("");
+
+ /*
+ * When recovering from a backup (we are in recovery, and archive recovery
+ * was requested), complain if we did not roll forward far enough to reach
+ * the point where the database is consistent. For regular online
+ * backup-from-primary, that means reaching the end-of-backup WAL record
+ * (at which point we reset backupStartPoint to be Invalid), for
+ * backup-from-replica (which can't inject records into the WAL stream),
+ * that point is when we reach the minRecoveryPoint in pg_control (which
+ * we purposefully copy last when backing up from a replica). For
+ * pg_rewind (which creates a backup_label with a method of "pg_rewind")
+ * or snapshot-style backups (which don't), backupEndRequired will be set
+ * to false.
+ *
+ * Note: it is indeed okay to look at the local variable
+ * LocalMinRecoveryPoint here, even though ControlFile->minRecoveryPoint
+ * might be further ahead --- ControlFile->minRecoveryPoint cannot have
+ * been advanced beyond the WAL we processed.
+ */
+ if (InRecovery &&
+ (EndOfLog < LocalMinRecoveryPoint ||
+ !XLogRecPtrIsInvalid(ControlFile->backupStartPoint)))
+ {
+ /*
+ * Ran off end of WAL before reaching end-of-backup WAL record, or
+ * minRecoveryPoint. That's a bad sign, indicating that you tried to
+ * recover from an online backup but never called pg_backup_stop(), or
+ * you didn't archive all the WAL needed.
+ */
+ if (ArchiveRecoveryRequested || ControlFile->backupEndRequired)
+ {
+ if (!XLogRecPtrIsInvalid(ControlFile->backupStartPoint) || ControlFile->backupEndRequired)
+ ereport(FATAL,
+ (errmsg("WAL ends before end of online backup"),
+ errhint("All WAL generated while online backup was taken must be available at recovery.")));
+ else
+ ereport(FATAL,
+ (errmsg("WAL ends before consistent recovery point")));
+ }
+ }
+
+ /*
+ * Reset unlogged relations to the contents of their INIT fork. This is
+ * done AFTER recovery is complete so as to include any unlogged relations
+ * created during recovery, but BEFORE recovery is marked as having
+ * completed successfully. Otherwise we'd not retry if any of the post
+ * end-of-recovery steps fail.
+ */
+ if (InRecovery)
+ ResetUnloggedRelations(UNLOGGED_RELATION_INIT);
+
+ /*
+ * Pre-scan prepared transactions to find out the range of XIDs present.
+ * This information is not quite needed yet, but it is positioned here so
+ * as potential problems are detected before any on-disk change is done.
+ */
+ oldestActiveXID = PrescanPreparedTransactions(NULL, NULL);
+
+ /*
+ * Allow ordinary WAL segment creation before possibly switching to a new
+ * timeline, which creates a new segment, and after the last ReadRecord().
+ */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ XLogCtl->InstallXLogFileSegmentActive = true;
+ LWLockRelease(ControlFileLock);
+
+ /*
+ * Consider whether we need to assign a new timeline ID.
+ *
+ * If we did archive recovery, we always assign a new ID. This handles a
+ * couple of issues. If we stopped short of the end of WAL during
+ * recovery, then we are clearly generating a new timeline and must assign
+ * it a unique new ID. Even if we ran to the end, modifying the current
+ * last segment is problematic because it may result in trying to
+ * overwrite an already-archived copy of that segment, and we encourage
+ * DBAs to make their archive_commands reject that. We can dodge the
+ * problem by making the new active segment have a new timeline ID.
+ *
+ * In a normal crash recovery, we can just extend the timeline we were in.
+ */
+ newTLI = endOfRecoveryInfo->lastRecTLI;
+ if (ArchiveRecoveryRequested)
+ {
+ newTLI = findNewestTimeLine(recoveryTargetTLI) + 1;
+ ereport(LOG,
+ (errmsg("selected new timeline ID: %u", newTLI)));
+
+ /*
+ * Make a writable copy of the last WAL segment. (Note that we also
+ * have a copy of the last block of the old WAL in
+ * endOfRecovery->lastPage; we will use that below.)
+ */
+ XLogInitNewTimeline(EndOfLogTLI, EndOfLog, newTLI);
+
+ /*
+ * Remove the signal files out of the way, so that we don't
+ * accidentally re-enter archive recovery mode in a subsequent crash.
+ */
+ if (endOfRecoveryInfo->standby_signal_file_found)
+ durable_unlink(STANDBY_SIGNAL_FILE, FATAL);
+
+ if (endOfRecoveryInfo->recovery_signal_file_found)
+ durable_unlink(RECOVERY_SIGNAL_FILE, FATAL);
+
+ /*
+ * Write the timeline history file, and have it archived. After this
+ * point (or rather, as soon as the file is archived), the timeline
+ * will appear as "taken" in the WAL archive and to any standby
+ * servers. If we crash before actually switching to the new
+ * timeline, standby servers will nevertheless think that we switched
+ * to the new timeline, and will try to connect to the new timeline.
+ * To minimize the window for that, try to do as little as possible
+ * between here and writing the end-of-recovery record.
+ */
+ writeTimeLineHistory(newTLI, recoveryTargetTLI,
+ EndOfLog, endOfRecoveryInfo->recoveryStopReason);
+
+ ereport(LOG,
+ (errmsg("archive recovery complete")));
+ }
+
+ /* Save the selected TimeLineID in shared memory, too */
+ XLogCtl->InsertTimeLineID = newTLI;
+ XLogCtl->PrevTimeLineID = endOfRecoveryInfo->lastRecTLI;
+
+ /*
+ * Actually, if WAL ended in an incomplete record, skip the parts that
+ * made it through and start writing after the portion that persisted.
+ * (It's critical to first write an OVERWRITE_CONTRECORD message, which
+ * we'll do as soon as we're open for writing new WAL.)
+ */
+ if (!XLogRecPtrIsInvalid(missingContrecPtr))
+ {
+ /*
+ * We should only have a missingContrecPtr if we're not switching to
+ * a new timeline. When a timeline switch occurs, WAL is copied from
+ * the old timeline to the new only up to the end of the last complete
+ * record, so there can't be an incomplete WAL record that we need to
+ * disregard.
+ */
+ Assert(newTLI == endOfRecoveryInfo->lastRecTLI);
+ Assert(!XLogRecPtrIsInvalid(abortedRecPtr));
+ EndOfLog = missingContrecPtr;
+ }
+
+ /*
+ * Prepare to write WAL starting at EndOfLog location, and init xlog
+ * buffer cache using the block containing the last record from the
+ * previous incarnation.
+ */
+ Insert = &XLogCtl->Insert;
+ Insert->PrevBytePos = XLogRecPtrToBytePos(endOfRecoveryInfo->lastRec);
+ Insert->CurrBytePos = XLogRecPtrToBytePos(EndOfLog);
+
+ /*
+ * Tricky point here: lastPage contains the *last* block that the LastRec
+ * record spans, not the one it starts in. The last block is indeed the
+ * one we want to use.
+ */
+ if (EndOfLog % XLOG_BLCKSZ != 0)
+ {
+ char *page;
+ int len;
+ int firstIdx;
+
+ firstIdx = XLogRecPtrToBufIdx(EndOfLog);
+ len = EndOfLog - endOfRecoveryInfo->lastPageBeginPtr;
+ Assert(len < XLOG_BLCKSZ);
+
+ /* Copy the valid part of the last block, and zero the rest */
+ page = &XLogCtl->pages[firstIdx * XLOG_BLCKSZ];
+ memcpy(page, endOfRecoveryInfo->lastPage, len);
+ memset(page + len, 0, XLOG_BLCKSZ - len);
+
+ XLogCtl->xlblocks[firstIdx] = endOfRecoveryInfo->lastPageBeginPtr + XLOG_BLCKSZ;
+ XLogCtl->InitializedUpTo = endOfRecoveryInfo->lastPageBeginPtr + XLOG_BLCKSZ;
+ }
+ else
+ {
+ /*
+ * There is no partial block to copy. Just set InitializedUpTo, and
+ * let the first attempt to insert a log record to initialize the next
+ * buffer.
+ */
+ XLogCtl->InitializedUpTo = EndOfLog;
+ }
+
+ LogwrtResult.Write = LogwrtResult.Flush = EndOfLog;
+
+ XLogCtl->LogwrtResult = LogwrtResult;
+
+ XLogCtl->LogwrtRqst.Write = EndOfLog;
+ XLogCtl->LogwrtRqst.Flush = EndOfLog;
+
+ /*
+ * Preallocate additional log files, if wanted.
+ */
+ PreallocXlogFiles(EndOfLog, newTLI);
+
+ /*
+ * Okay, we're officially UP.
+ */
+ InRecovery = false;
+
+ /* start the archive_timeout timer and LSN running */
+ XLogCtl->lastSegSwitchTime = (pg_time_t) time(NULL);
+ XLogCtl->lastSegSwitchLSN = EndOfLog;
+
+ /* also initialize latestCompletedXid, to nextXid - 1 */
+ LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
+ ShmemVariableCache->latestCompletedXid = ShmemVariableCache->nextXid;
+ FullTransactionIdRetreat(&ShmemVariableCache->latestCompletedXid);
+ LWLockRelease(ProcArrayLock);
+
+ /*
+ * Start up subtrans, if not already done for hot standby. (commit
+ * timestamps are started below, if necessary.)
+ */
+ if (standbyState == STANDBY_DISABLED)
+ StartupSUBTRANS(oldestActiveXID);
+
+ /*
+ * Perform end of recovery actions for any SLRUs that need it.
+ */
+ TrimCLOG();
+ TrimMultiXact();
+
+ /*
+ * Reload shared-memory state for prepared transactions. This needs to
+ * happen before renaming the last partial segment of the old timeline as
+ * it may be possible that we have to recovery some transactions from it.
+ */
+ RecoverPreparedTransactions();
+
+ /* Shut down xlogreader */
+ ShutdownWalRecovery();
+
+ /* Enable WAL writes for this backend only. */
+ LocalSetXLogInsertAllowed();
+
+ /* If necessary, write overwrite-contrecord before doing anything else */
+ if (!XLogRecPtrIsInvalid(abortedRecPtr))
+ {
+ Assert(!XLogRecPtrIsInvalid(missingContrecPtr));
+ CreateOverwriteContrecordRecord(abortedRecPtr, missingContrecPtr, newTLI);
+ }
+
+ /*
+ * Update full_page_writes in shared memory and write an XLOG_FPW_CHANGE
+ * record before resource manager writes cleanup WAL records or checkpoint
+ * record is written.
+ */
+ Insert->fullPageWrites = lastFullPageWrites;
+ UpdateFullPageWrites();
+
+ /*
+ * Emit checkpoint or end-of-recovery record in XLOG, if required.
+ */
+ if (performedWalRecovery)
+ promoted = PerformRecoveryXLogAction();
+
+ /*
+ * If any of the critical GUCs have changed, log them before we allow
+ * backends to write WAL.
+ */
+ XLogReportParameters();
+
+ /* If this is archive recovery, perform post-recovery cleanup actions. */
+ if (ArchiveRecoveryRequested)
+ CleanupAfterArchiveRecovery(EndOfLogTLI, EndOfLog, newTLI);
+
+ /*
+ * Local WAL inserts enabled, so it's time to finish initialization of
+ * commit timestamp.
+ */
+ CompleteCommitTsInitialization();
+
+ /*
+ * All done with end-of-recovery actions.
+ *
+ * Now allow backends to write WAL and update the control file status in
+ * consequence. SharedRecoveryState, that controls if backends can write
+ * WAL, is updated while holding ControlFileLock to prevent other backends
+ * to look at an inconsistent state of the control file in shared memory.
+ * There is still a small window during which backends can write WAL and
+ * the control file is still referring to a system not in DB_IN_PRODUCTION
+ * state while looking at the on-disk control file.
+ *
+ * Also, we use info_lck to update SharedRecoveryState to ensure that
+ * there are no race conditions concerning visibility of other recent
+ * updates to shared memory.
+ */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->state = DB_IN_PRODUCTION;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->SharedRecoveryState = RECOVERY_STATE_DONE;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ UpdateControlFile();
+ LWLockRelease(ControlFileLock);
+
+ /*
+ * Shutdown the recovery environment. This must occur after
+ * RecoverPreparedTransactions() (see notes in lock_twophase_recover())
+ * and after switching SharedRecoveryState to RECOVERY_STATE_DONE so as
+ * any session building a snapshot will not rely on KnownAssignedXids as
+ * RecoveryInProgress() would return false at this stage. This is
+ * particularly critical for prepared 2PC transactions, that would still
+ * need to be included in snapshots once recovery has ended.
+ */
+ if (standbyState != STANDBY_DISABLED)
+ ShutdownRecoveryTransactionEnvironment();
+
+ /*
+ * If there were cascading standby servers connected to us, nudge any wal
+ * sender processes to notice that we've been promoted.
+ */
+ WalSndWakeup();
+
+ /*
+ * If this was a promotion, request an (online) checkpoint now. This isn't
+ * required for consistency, but the last restartpoint might be far back,
+ * and in case of a crash, recovering from it might take a longer than is
+ * appropriate now that we're not in standby mode anymore.
+ */
+ if (promoted)
+ RequestCheckpoint(CHECKPOINT_FORCE);
+}
+
+/*
+ * Callback from PerformWalRecovery(), called when we switch from crash
+ * recovery to archive recovery mode. Updates the control file accordingly.
+ */
+void
+SwitchIntoArchiveRecovery(XLogRecPtr EndRecPtr, TimeLineID replayTLI)
+{
+ /* initialize minRecoveryPoint to this record */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->state = DB_IN_ARCHIVE_RECOVERY;
+ if (ControlFile->minRecoveryPoint < EndRecPtr)
+ {
+ ControlFile->minRecoveryPoint = EndRecPtr;
+ ControlFile->minRecoveryPointTLI = replayTLI;
+ }
+ /* update local copy */
+ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint;
+ LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
+
+ /*
+ * The startup process can update its local copy of minRecoveryPoint from
+ * this point.
+ */
+ updateMinRecoveryPoint = true;
+
+ UpdateControlFile();
+
+ /*
+ * We update SharedRecoveryState while holding the lock on ControlFileLock
+ * so both states are consistent in shared memory.
+ */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->SharedRecoveryState = RECOVERY_STATE_ARCHIVE;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ LWLockRelease(ControlFileLock);
+}
+
+/*
+ * Callback from PerformWalRecovery(), called when we reach the end of backup.
+ * Updates the control file accordingly.
+ */
+void
+ReachedEndOfBackup(XLogRecPtr EndRecPtr, TimeLineID tli)
+{
+ /*
+ * We have reached the end of base backup, as indicated by pg_control. The
+ * data on disk is now consistent (unless minRecovery point is further
+ * ahead, which can happen if we crashed during previous recovery). Reset
+ * backupStartPoint and backupEndPoint, and update minRecoveryPoint to
+ * make sure we don't allow starting up at an earlier point even if
+ * recovery is stopped and restarted soon after this.
+ */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+
+ if (ControlFile->minRecoveryPoint < EndRecPtr)
+ {
+ ControlFile->minRecoveryPoint = EndRecPtr;
+ ControlFile->minRecoveryPointTLI = tli;
+ }
+
+ ControlFile->backupStartPoint = InvalidXLogRecPtr;
+ ControlFile->backupEndPoint = InvalidXLogRecPtr;
+ ControlFile->backupEndRequired = false;
+ UpdateControlFile();
+
+ LWLockRelease(ControlFileLock);
+}
+
+/*
+ * Perform whatever XLOG actions are necessary at end of REDO.
+ *
+ * The goal here is to make sure that we'll be able to recover properly if
+ * we crash again. If we choose to write a checkpoint, we'll write a shutdown
+ * checkpoint rather than an on-line one. This is not particularly critical,
+ * but since we may be assigning a new TLI, using a shutdown checkpoint allows
+ * us to have the rule that TLI only changes in shutdown checkpoints, which
+ * allows some extra error checking in xlog_redo.
+ */
+static bool
+PerformRecoveryXLogAction(void)
+{
+ bool promoted = false;
+
+ /*
+ * Perform a checkpoint to update all our recovery activity to disk.
+ *
+ * Note that we write a shutdown checkpoint rather than an on-line one.
+ * This is not particularly critical, but since we may be assigning a new
+ * TLI, using a shutdown checkpoint allows us to have the rule that TLI
+ * only changes in shutdown checkpoints, which allows some extra error
+ * checking in xlog_redo.
+ *
+ * In promotion, only create a lightweight end-of-recovery record instead
+ * of a full checkpoint. A checkpoint is requested later, after we're
+ * fully out of recovery mode and already accepting queries.
+ */
+ if (ArchiveRecoveryRequested && IsUnderPostmaster &&
+ PromoteIsTriggered())
+ {
+ promoted = true;
+
+ /*
+ * Insert a special WAL record to mark the end of recovery, since we
+ * aren't doing a checkpoint. That means that the checkpointer process
+ * may likely be in the middle of a time-smoothed restartpoint and
+ * could continue to be for minutes after this. That sounds strange,
+ * but the effect is roughly the same and it would be stranger to try
+ * to come out of the restartpoint and then checkpoint. We request a
+ * checkpoint later anyway, just for safety.
+ */
+ CreateEndOfRecoveryRecord();
+ }
+ else
+ {
+ RequestCheckpoint(CHECKPOINT_END_OF_RECOVERY |
+ CHECKPOINT_IMMEDIATE |
+ CHECKPOINT_WAIT);
+ }
+
+ return promoted;
+}
+
+/*
+ * Is the system still in recovery?
+ *
+ * Unlike testing InRecovery, this works in any process that's connected to
+ * shared memory.
+ */
+bool
+RecoveryInProgress(void)
+{
+ /*
+ * We check shared state each time only until we leave recovery mode. We
+ * can't re-enter recovery, so there's no need to keep checking after the
+ * shared variable has once been seen false.
+ */
+ if (!LocalRecoveryInProgress)
+ return false;
+ else
+ {
+ /*
+ * use volatile pointer to make sure we make a fresh read of the
+ * shared variable.
+ */
+ volatile XLogCtlData *xlogctl = XLogCtl;
+
+ LocalRecoveryInProgress = (xlogctl->SharedRecoveryState != RECOVERY_STATE_DONE);
+
+ /*
+ * Note: We don't need a memory barrier when we're still in recovery.
+ * We might exit recovery immediately after return, so the caller
+ * can't rely on 'true' meaning that we're still in recovery anyway.
+ */
+
+ return LocalRecoveryInProgress;
+ }
+}
+
+/*
+ * Returns current recovery state from shared memory.
+ *
+ * This returned state is kept consistent with the contents of the control
+ * file. See details about the possible values of RecoveryState in xlog.h.
+ */
+RecoveryState
+GetRecoveryState(void)
+{
+ RecoveryState retval;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ retval = XLogCtl->SharedRecoveryState;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ return retval;
+}
+
+/*
+ * Is this process allowed to insert new WAL records?
+ *
+ * Ordinarily this is essentially equivalent to !RecoveryInProgress().
+ * But we also have provisions for forcing the result "true" or "false"
+ * within specific processes regardless of the global state.
+ */
+bool
+XLogInsertAllowed(void)
+{
+ /*
+ * If value is "unconditionally true" or "unconditionally false", just
+ * return it. This provides the normal fast path once recovery is known
+ * done.
+ */
+ if (LocalXLogInsertAllowed >= 0)
+ return (bool) LocalXLogInsertAllowed;
+
+ /*
+ * Else, must check to see if we're still in recovery.
+ */
+ if (RecoveryInProgress())
+ return false;
+
+ /*
+ * On exit from recovery, reset to "unconditionally true", since there is
+ * no need to keep checking.
+ */
+ LocalXLogInsertAllowed = 1;
+ return true;
+}
+
+/*
+ * Make XLogInsertAllowed() return true in the current process only.
+ *
+ * Note: it is allowed to switch LocalXLogInsertAllowed back to -1 later,
+ * and even call LocalSetXLogInsertAllowed() again after that.
+ *
+ * Returns the previous value of LocalXLogInsertAllowed.
+ */
+static int
+LocalSetXLogInsertAllowed(void)
+{
+ int oldXLogAllowed = LocalXLogInsertAllowed;
+
+ LocalXLogInsertAllowed = 1;
+
+ return oldXLogAllowed;
+}
+
+/*
+ * Return the current Redo pointer from shared memory.
+ *
+ * As a side-effect, the local RedoRecPtr copy is updated.
+ */
+XLogRecPtr
+GetRedoRecPtr(void)
+{
+ XLogRecPtr ptr;
+
+ /*
+ * The possibly not up-to-date copy in XlogCtl is enough. Even if we
+ * grabbed a WAL insertion lock to read the authoritative value in
+ * Insert->RedoRecPtr, someone might update it just after we've released
+ * the lock.
+ */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ ptr = XLogCtl->RedoRecPtr;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ if (RedoRecPtr < ptr)
+ RedoRecPtr = ptr;
+
+ return RedoRecPtr;
+}
+
+/*
+ * Return information needed to decide whether a modified block needs a
+ * full-page image to be included in the WAL record.
+ *
+ * The returned values are cached copies from backend-private memory, and
+ * possibly out-of-date or, indeed, uninitialized, in which case they will
+ * be InvalidXLogRecPtr and false, respectively. XLogInsertRecord will
+ * re-check them against up-to-date values, while holding the WAL insert lock.
+ */
+void
+GetFullPageWriteInfo(XLogRecPtr *RedoRecPtr_p, bool *doPageWrites_p)
+{
+ *RedoRecPtr_p = RedoRecPtr;
+ *doPageWrites_p = doPageWrites;
+}
+
+/*
+ * GetInsertRecPtr -- Returns the current insert position.
+ *
+ * NOTE: The value *actually* returned is the position of the last full
+ * xlog page. It lags behind the real insert position by at most 1 page.
+ * For that, we don't need to scan through WAL insertion locks, and an
+ * approximation is enough for the current usage of this function.
+ */
+XLogRecPtr
+GetInsertRecPtr(void)
+{
+ XLogRecPtr recptr;
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ recptr = XLogCtl->LogwrtRqst.Write;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ return recptr;
+}
+
+/*
+ * GetFlushRecPtr -- Returns the current flush position, ie, the last WAL
+ * position known to be fsync'd to disk. This should only be used on a
+ * system that is known not to be in recovery.
+ */
+XLogRecPtr
+GetFlushRecPtr(TimeLineID *insertTLI)
+{
+ Assert(XLogCtl->SharedRecoveryState == RECOVERY_STATE_DONE);
+
+ SpinLockAcquire(&XLogCtl->info_lck);
+ LogwrtResult = XLogCtl->LogwrtResult;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * If we're writing and flushing WAL, the time line can't be changing, so
+ * no lock is required.
+ */
+ if (insertTLI)
+ *insertTLI = XLogCtl->InsertTimeLineID;
+
+ return LogwrtResult.Flush;
+}
+
+/*
+ * GetWALInsertionTimeLine -- Returns the current timeline of a system that
+ * is not in recovery.
+ */
+TimeLineID
+GetWALInsertionTimeLine(void)
+{
+ Assert(XLogCtl->SharedRecoveryState == RECOVERY_STATE_DONE);
+
+ /* Since the value can't be changing, no lock is required. */
+ return XLogCtl->InsertTimeLineID;
+}
+
+/*
+ * GetLastImportantRecPtr -- Returns the LSN of the last important record
+ * inserted. All records not explicitly marked as unimportant are considered
+ * important.
+ *
+ * The LSN is determined by computing the maximum of
+ * WALInsertLocks[i].lastImportantAt.
+ */
+XLogRecPtr
+GetLastImportantRecPtr(void)
+{
+ XLogRecPtr res = InvalidXLogRecPtr;
+ int i;
+
+ for (i = 0; i < NUM_XLOGINSERT_LOCKS; i++)
+ {
+ XLogRecPtr last_important;
+
+ /*
+ * Need to take a lock to prevent torn reads of the LSN, which are
+ * possible on some of the supported platforms. WAL insert locks only
+ * support exclusive mode, so we have to use that.
+ */
+ LWLockAcquire(&WALInsertLocks[i].l.lock, LW_EXCLUSIVE);
+ last_important = WALInsertLocks[i].l.lastImportantAt;
+ LWLockRelease(&WALInsertLocks[i].l.lock);
+
+ if (res < last_important)
+ res = last_important;
+ }
+
+ return res;
+}
+
+/*
+ * Get the time and LSN of the last xlog segment switch
+ */
+pg_time_t
+GetLastSegSwitchData(XLogRecPtr *lastSwitchLSN)
+{
+ pg_time_t result;
+
+ /* Need WALWriteLock, but shared lock is sufficient */
+ LWLockAcquire(WALWriteLock, LW_SHARED);
+ result = XLogCtl->lastSegSwitchTime;
+ *lastSwitchLSN = XLogCtl->lastSegSwitchLSN;
+ LWLockRelease(WALWriteLock);
+
+ return result;
+}
+
+/*
+ * This must be called ONCE during postmaster or standalone-backend shutdown
+ */
+void
+ShutdownXLOG(int code, Datum arg)
+{
+ /*
+ * We should have an aux process resource owner to use, and we should not
+ * be in a transaction that's installed some other resowner.
+ */
+ Assert(AuxProcessResourceOwner != NULL);
+ Assert(CurrentResourceOwner == NULL ||
+ CurrentResourceOwner == AuxProcessResourceOwner);
+ CurrentResourceOwner = AuxProcessResourceOwner;
+
+ /* Don't be chatty in standalone mode */
+ ereport(IsPostmasterEnvironment ? LOG : NOTICE,
+ (errmsg("shutting down")));
+
+ /*
+ * Signal walsenders to move to stopping state.
+ */
+ WalSndInitStopping();
+
+ /*
+ * Wait for WAL senders to be in stopping state. This prevents commands
+ * from writing new WAL.
+ */
+ WalSndWaitStopping();
+
+ if (RecoveryInProgress())
+ CreateRestartPoint(CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_IMMEDIATE);
+ else
+ {
+ /*
+ * If archiving is enabled, rotate the last XLOG file so that all the
+ * remaining records are archived (postmaster wakes up the archiver
+ * process one more time at the end of shutdown). The checkpoint
+ * record will go to the next XLOG file and won't be archived (yet).
+ */
+ if (XLogArchivingActive())
+ RequestXLogSwitch(false);
+
+ CreateCheckPoint(CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_IMMEDIATE);
+ }
+}
+
+/*
+ * Log start of a checkpoint.
+ */
+static void
+LogCheckpointStart(int flags, bool restartpoint)
+{
+ if (restartpoint)
+ ereport(LOG,
+ /* translator: the placeholders show checkpoint options */
+ (errmsg("restartpoint starting:%s%s%s%s%s%s%s%s",
+ (flags & CHECKPOINT_IS_SHUTDOWN) ? " shutdown" : "",
+ (flags & CHECKPOINT_END_OF_RECOVERY) ? " end-of-recovery" : "",
+ (flags & CHECKPOINT_IMMEDIATE) ? " immediate" : "",
+ (flags & CHECKPOINT_FORCE) ? " force" : "",
+ (flags & CHECKPOINT_WAIT) ? " wait" : "",
+ (flags & CHECKPOINT_CAUSE_XLOG) ? " wal" : "",
+ (flags & CHECKPOINT_CAUSE_TIME) ? " time" : "",
+ (flags & CHECKPOINT_FLUSH_ALL) ? " flush-all" : "")));
+ else
+ ereport(LOG,
+ /* translator: the placeholders show checkpoint options */
+ (errmsg("checkpoint starting:%s%s%s%s%s%s%s%s",
+ (flags & CHECKPOINT_IS_SHUTDOWN) ? " shutdown" : "",
+ (flags & CHECKPOINT_END_OF_RECOVERY) ? " end-of-recovery" : "",
+ (flags & CHECKPOINT_IMMEDIATE) ? " immediate" : "",
+ (flags & CHECKPOINT_FORCE) ? " force" : "",
+ (flags & CHECKPOINT_WAIT) ? " wait" : "",
+ (flags & CHECKPOINT_CAUSE_XLOG) ? " wal" : "",
+ (flags & CHECKPOINT_CAUSE_TIME) ? " time" : "",
+ (flags & CHECKPOINT_FLUSH_ALL) ? " flush-all" : "")));
+}
+
+/*
+ * Log end of a checkpoint.
+ */
+static void
+LogCheckpointEnd(bool restartpoint)
+{
+ long write_msecs,
+ sync_msecs,
+ total_msecs,
+ longest_msecs,
+ average_msecs;
+ uint64 average_sync_time;
+
+ CheckpointStats.ckpt_end_t = GetCurrentTimestamp();
+
+ write_msecs = TimestampDifferenceMilliseconds(CheckpointStats.ckpt_write_t,
+ CheckpointStats.ckpt_sync_t);
+
+ sync_msecs = TimestampDifferenceMilliseconds(CheckpointStats.ckpt_sync_t,
+ CheckpointStats.ckpt_sync_end_t);
+
+ /* Accumulate checkpoint timing summary data, in milliseconds. */
+ PendingCheckpointerStats.checkpoint_write_time += write_msecs;
+ PendingCheckpointerStats.checkpoint_sync_time += sync_msecs;
+
+ /*
+ * All of the published timing statistics are accounted for. Only
+ * continue if a log message is to be written.
+ */
+ if (!log_checkpoints)
+ return;
+
+ total_msecs = TimestampDifferenceMilliseconds(CheckpointStats.ckpt_start_t,
+ CheckpointStats.ckpt_end_t);
+
+ /*
+ * Timing values returned from CheckpointStats are in microseconds.
+ * Convert to milliseconds for consistent printing.
+ */
+ longest_msecs = (long) ((CheckpointStats.ckpt_longest_sync + 999) / 1000);
+
+ average_sync_time = 0;
+ if (CheckpointStats.ckpt_sync_rels > 0)
+ average_sync_time = CheckpointStats.ckpt_agg_sync_time /
+ CheckpointStats.ckpt_sync_rels;
+ average_msecs = (long) ((average_sync_time + 999) / 1000);
+
+ if (restartpoint)
+ ereport(LOG,
+ (errmsg("restartpoint complete: wrote %d buffers (%.1f%%); "
+ "%d WAL file(s) added, %d removed, %d recycled; "
+ "write=%ld.%03d s, sync=%ld.%03d s, total=%ld.%03d s; "
+ "sync files=%d, longest=%ld.%03d s, average=%ld.%03d s; "
+ "distance=%d kB, estimate=%d kB",
+ CheckpointStats.ckpt_bufs_written,
+ (double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers,
+ CheckpointStats.ckpt_segs_added,
+ CheckpointStats.ckpt_segs_removed,
+ CheckpointStats.ckpt_segs_recycled,
+ write_msecs / 1000, (int) (write_msecs % 1000),
+ sync_msecs / 1000, (int) (sync_msecs % 1000),
+ total_msecs / 1000, (int) (total_msecs % 1000),
+ CheckpointStats.ckpt_sync_rels,
+ longest_msecs / 1000, (int) (longest_msecs % 1000),
+ average_msecs / 1000, (int) (average_msecs % 1000),
+ (int) (PrevCheckPointDistance / 1024.0),
+ (int) (CheckPointDistanceEstimate / 1024.0))));
+ else
+ ereport(LOG,
+ (errmsg("checkpoint complete: wrote %d buffers (%.1f%%); "
+ "%d WAL file(s) added, %d removed, %d recycled; "
+ "write=%ld.%03d s, sync=%ld.%03d s, total=%ld.%03d s; "
+ "sync files=%d, longest=%ld.%03d s, average=%ld.%03d s; "
+ "distance=%d kB, estimate=%d kB",
+ CheckpointStats.ckpt_bufs_written,
+ (double) CheckpointStats.ckpt_bufs_written * 100 / NBuffers,
+ CheckpointStats.ckpt_segs_added,
+ CheckpointStats.ckpt_segs_removed,
+ CheckpointStats.ckpt_segs_recycled,
+ write_msecs / 1000, (int) (write_msecs % 1000),
+ sync_msecs / 1000, (int) (sync_msecs % 1000),
+ total_msecs / 1000, (int) (total_msecs % 1000),
+ CheckpointStats.ckpt_sync_rels,
+ longest_msecs / 1000, (int) (longest_msecs % 1000),
+ average_msecs / 1000, (int) (average_msecs % 1000),
+ (int) (PrevCheckPointDistance / 1024.0),
+ (int) (CheckPointDistanceEstimate / 1024.0))));
+}
+
+/*
+ * Update the estimate of distance between checkpoints.
+ *
+ * The estimate is used to calculate the number of WAL segments to keep
+ * preallocated, see XLOGfileslop().
+ */
+static void
+UpdateCheckPointDistanceEstimate(uint64 nbytes)
+{
+ /*
+ * To estimate the number of segments consumed between checkpoints, keep a
+ * moving average of the amount of WAL generated in previous checkpoint
+ * cycles. However, if the load is bursty, with quiet periods and busy
+ * periods, we want to cater for the peak load. So instead of a plain
+ * moving average, let the average decline slowly if the previous cycle
+ * used less WAL than estimated, but bump it up immediately if it used
+ * more.
+ *
+ * When checkpoints are triggered by max_wal_size, this should converge to
+ * CheckpointSegments * wal_segment_size,
+ *
+ * Note: This doesn't pay any attention to what caused the checkpoint.
+ * Checkpoints triggered manually with CHECKPOINT command, or by e.g.
+ * starting a base backup, are counted the same as those created
+ * automatically. The slow-decline will largely mask them out, if they are
+ * not frequent. If they are frequent, it seems reasonable to count them
+ * in as any others; if you issue a manual checkpoint every 5 minutes and
+ * never let a timed checkpoint happen, it makes sense to base the
+ * preallocation on that 5 minute interval rather than whatever
+ * checkpoint_timeout is set to.
+ */
+ PrevCheckPointDistance = nbytes;
+ if (CheckPointDistanceEstimate < nbytes)
+ CheckPointDistanceEstimate = nbytes;
+ else
+ CheckPointDistanceEstimate =
+ (0.90 * CheckPointDistanceEstimate + 0.10 * (double) nbytes);
+}
+
+/*
+ * Update the ps display for a process running a checkpoint. Note that
+ * this routine should not do any allocations so as it can be called
+ * from a critical section.
+ */
+static void
+update_checkpoint_display(int flags, bool restartpoint, bool reset)
+{
+ /*
+ * The status is reported only for end-of-recovery and shutdown
+ * checkpoints or shutdown restartpoints. Updating the ps display is
+ * useful in those situations as it may not be possible to rely on
+ * pg_stat_activity to see the status of the checkpointer or the startup
+ * process.
+ */
+ if ((flags & (CHECKPOINT_END_OF_RECOVERY | CHECKPOINT_IS_SHUTDOWN)) == 0)
+ return;
+
+ if (reset)
+ set_ps_display("");
+ else
+ {
+ char activitymsg[128];
+
+ snprintf(activitymsg, sizeof(activitymsg), "performing %s%s%s",
+ (flags & CHECKPOINT_END_OF_RECOVERY) ? "end-of-recovery " : "",
+ (flags & CHECKPOINT_IS_SHUTDOWN) ? "shutdown " : "",
+ restartpoint ? "restartpoint" : "checkpoint");
+ set_ps_display(activitymsg);
+ }
+}
+
+
+/*
+ * Perform a checkpoint --- either during shutdown, or on-the-fly
+ *
+ * flags is a bitwise OR of the following:
+ * CHECKPOINT_IS_SHUTDOWN: checkpoint is for database shutdown.
+ * CHECKPOINT_END_OF_RECOVERY: checkpoint is for end of WAL recovery.
+ * CHECKPOINT_IMMEDIATE: finish the checkpoint ASAP,
+ * ignoring checkpoint_completion_target parameter.
+ * CHECKPOINT_FORCE: force a checkpoint even if no XLOG activity has occurred
+ * since the last one (implied by CHECKPOINT_IS_SHUTDOWN or
+ * CHECKPOINT_END_OF_RECOVERY).
+ * CHECKPOINT_FLUSH_ALL: also flush buffers of unlogged tables.
+ *
+ * Note: flags contains other bits, of interest here only for logging purposes.
+ * In particular note that this routine is synchronous and does not pay
+ * attention to CHECKPOINT_WAIT.
+ *
+ * If !shutdown then we are writing an online checkpoint. This is a very special
+ * kind of operation and WAL record because the checkpoint action occurs over
+ * a period of time yet logically occurs at just a single LSN. The logical
+ * position of the WAL record (redo ptr) is the same or earlier than the
+ * physical position. When we replay WAL we locate the checkpoint via its
+ * physical position then read the redo ptr and actually start replay at the
+ * earlier logical position. Note that we don't write *anything* to WAL at
+ * the logical position, so that location could be any other kind of WAL record.
+ * All of this mechanism allows us to continue working while we checkpoint.
+ * As a result, timing of actions is critical here and be careful to note that
+ * this function will likely take minutes to execute on a busy system.
+ */
+void
+CreateCheckPoint(int flags)
+{
+ bool shutdown;
+ CheckPoint checkPoint;
+ XLogRecPtr recptr;
+ XLogSegNo _logSegNo;
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ uint32 freespace;
+ XLogRecPtr PriorRedoPtr;
+ XLogRecPtr curInsert;
+ XLogRecPtr last_important_lsn;
+ VirtualTransactionId *vxids;
+ int nvxids;
+ int oldXLogAllowed = 0;
+
+ /*
+ * An end-of-recovery checkpoint is really a shutdown checkpoint, just
+ * issued at a different time.
+ */
+ if (flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY))
+ shutdown = true;
+ else
+ shutdown = false;
+
+ /* sanity check */
+ if (RecoveryInProgress() && (flags & CHECKPOINT_END_OF_RECOVERY) == 0)
+ elog(ERROR, "can't create a checkpoint during recovery");
+
+ /*
+ * Prepare to accumulate statistics.
+ *
+ * Note: because it is possible for log_checkpoints to change while a
+ * checkpoint proceeds, we always accumulate stats, even if
+ * log_checkpoints is currently off.
+ */
+ MemSet(&CheckpointStats, 0, sizeof(CheckpointStats));
+ CheckpointStats.ckpt_start_t = GetCurrentTimestamp();
+
+ /*
+ * Let smgr prepare for checkpoint; this has to happen outside the
+ * critical section and before we determine the REDO pointer. Note that
+ * smgr must not do anything that'd have to be undone if we decide no
+ * checkpoint is needed.
+ */
+ SyncPreCheckpoint();
+
+ /*
+ * Use a critical section to force system panic if we have trouble.
+ */
+ START_CRIT_SECTION();
+
+ if (shutdown)
+ {
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->state = DB_SHUTDOWNING;
+ UpdateControlFile();
+ LWLockRelease(ControlFileLock);
+ }
+
+ /* Begin filling in the checkpoint WAL record */
+ MemSet(&checkPoint, 0, sizeof(checkPoint));
+ checkPoint.time = (pg_time_t) time(NULL);
+
+ /*
+ * For Hot Standby, derive the oldestActiveXid before we fix the redo
+ * pointer. This allows us to begin accumulating changes to assemble our
+ * starting snapshot of locks and transactions.
+ */
+ if (!shutdown && XLogStandbyInfoActive())
+ checkPoint.oldestActiveXid = GetOldestActiveTransactionId();
+ else
+ checkPoint.oldestActiveXid = InvalidTransactionId;
+
+ /*
+ * Get location of last important record before acquiring insert locks (as
+ * GetLastImportantRecPtr() also locks WAL locks).
+ */
+ last_important_lsn = GetLastImportantRecPtr();
+
+ /*
+ * We must block concurrent insertions while examining insert state to
+ * determine the checkpoint REDO pointer.
+ */
+ WALInsertLockAcquireExclusive();
+ curInsert = XLogBytePosToRecPtr(Insert->CurrBytePos);
+
+ /*
+ * If this isn't a shutdown or forced checkpoint, and if there has been no
+ * WAL activity requiring a checkpoint, skip it. The idea here is to
+ * avoid inserting duplicate checkpoints when the system is idle.
+ */
+ if ((flags & (CHECKPOINT_IS_SHUTDOWN | CHECKPOINT_END_OF_RECOVERY |
+ CHECKPOINT_FORCE)) == 0)
+ {
+ if (last_important_lsn == ControlFile->checkPoint)
+ {
+ WALInsertLockRelease();
+ END_CRIT_SECTION();
+ ereport(DEBUG1,
+ (errmsg_internal("checkpoint skipped because system is idle")));
+ return;
+ }
+ }
+
+ /*
+ * An end-of-recovery checkpoint is created before anyone is allowed to
+ * write WAL. To allow us to write the checkpoint record, temporarily
+ * enable XLogInsertAllowed.
+ */
+ if (flags & CHECKPOINT_END_OF_RECOVERY)
+ oldXLogAllowed = LocalSetXLogInsertAllowed();
+
+ checkPoint.ThisTimeLineID = XLogCtl->InsertTimeLineID;
+ if (flags & CHECKPOINT_END_OF_RECOVERY)
+ checkPoint.PrevTimeLineID = XLogCtl->PrevTimeLineID;
+ else
+ checkPoint.PrevTimeLineID = checkPoint.ThisTimeLineID;
+
+ checkPoint.fullPageWrites = Insert->fullPageWrites;
+
+ /*
+ * Compute new REDO record ptr = location of next XLOG record.
+ *
+ * NB: this is NOT necessarily where the checkpoint record itself will be,
+ * since other backends may insert more XLOG records while we're off doing
+ * the buffer flush work. Those XLOG records are logically after the
+ * checkpoint, even though physically before it. Got that?
+ */
+ freespace = INSERT_FREESPACE(curInsert);
+ if (freespace == 0)
+ {
+ if (XLogSegmentOffset(curInsert, wal_segment_size) == 0)
+ curInsert += SizeOfXLogLongPHD;
+ else
+ curInsert += SizeOfXLogShortPHD;
+ }
+ checkPoint.redo = curInsert;
+
+ /*
+ * Here we update the shared RedoRecPtr for future XLogInsert calls; this
+ * must be done while holding all the insertion locks.
+ *
+ * Note: if we fail to complete the checkpoint, RedoRecPtr will be left
+ * pointing past where it really needs to point. This is okay; the only
+ * consequence is that XLogInsert might back up whole buffers that it
+ * didn't really need to. We can't postpone advancing RedoRecPtr because
+ * XLogInserts that happen while we are dumping buffers must assume that
+ * their buffer changes are not included in the checkpoint.
+ */
+ RedoRecPtr = XLogCtl->Insert.RedoRecPtr = checkPoint.redo;
+
+ /*
+ * Now we can release the WAL insertion locks, allowing other xacts to
+ * proceed while we are flushing disk buffers.
+ */
+ WALInsertLockRelease();
+
+ /* Update the info_lck-protected copy of RedoRecPtr as well */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->RedoRecPtr = checkPoint.redo;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * If enabled, log checkpoint start. We postpone this until now so as not
+ * to log anything if we decided to skip the checkpoint.
+ */
+ if (log_checkpoints)
+ LogCheckpointStart(flags, false);
+
+ /* Update the process title */
+ update_checkpoint_display(flags, false, false);
+
+ TRACE_POSTGRESQL_CHECKPOINT_START(flags);
+
+ /*
+ * Get the other info we need for the checkpoint record.
+ *
+ * We don't need to save oldestClogXid in the checkpoint, it only matters
+ * for the short period in which clog is being truncated, and if we crash
+ * during that we'll redo the clog truncation and fix up oldestClogXid
+ * there.
+ */
+ LWLockAcquire(XidGenLock, LW_SHARED);
+ checkPoint.nextXid = ShmemVariableCache->nextXid;
+ checkPoint.oldestXid = ShmemVariableCache->oldestXid;
+ checkPoint.oldestXidDB = ShmemVariableCache->oldestXidDB;
+ LWLockRelease(XidGenLock);
+
+ LWLockAcquire(CommitTsLock, LW_SHARED);
+ checkPoint.oldestCommitTsXid = ShmemVariableCache->oldestCommitTsXid;
+ checkPoint.newestCommitTsXid = ShmemVariableCache->newestCommitTsXid;
+ LWLockRelease(CommitTsLock);
+
+ LWLockAcquire(OidGenLock, LW_SHARED);
+ checkPoint.nextOid = ShmemVariableCache->nextOid;
+ if (!shutdown)
+ checkPoint.nextOid += ShmemVariableCache->oidCount;
+ LWLockRelease(OidGenLock);
+
+ MultiXactGetCheckptMulti(shutdown,
+ &checkPoint.nextMulti,
+ &checkPoint.nextMultiOffset,
+ &checkPoint.oldestMulti,
+ &checkPoint.oldestMultiDB);
+
+ /*
+ * Having constructed the checkpoint record, ensure all shmem disk buffers
+ * and commit-log buffers are flushed to disk.
+ *
+ * This I/O could fail for various reasons. If so, we will fail to
+ * complete the checkpoint, but there is no reason to force a system
+ * panic. Accordingly, exit critical section while doing it.
+ */
+ END_CRIT_SECTION();
+
+ /*
+ * In some cases there are groups of actions that must all occur on one
+ * side or the other of a checkpoint record. Before flushing the
+ * checkpoint record we must explicitly wait for any backend currently
+ * performing those groups of actions.
+ *
+ * One example is end of transaction, so we must wait for any transactions
+ * that are currently in commit critical sections. If an xact inserted
+ * its commit record into XLOG just before the REDO point, then a crash
+ * restart from the REDO point would not replay that record, which means
+ * that our flushing had better include the xact's update of pg_xact. So
+ * we wait till he's out of his commit critical section before proceeding.
+ * See notes in RecordTransactionCommit().
+ *
+ * Because we've already released the insertion locks, this test is a bit
+ * fuzzy: it is possible that we will wait for xacts we didn't really need
+ * to wait for. But the delay should be short and it seems better to make
+ * checkpoint take a bit longer than to hold off insertions longer than
+ * necessary. (In fact, the whole reason we have this issue is that xact.c
+ * does commit record XLOG insertion and clog update as two separate steps
+ * protected by different locks, but again that seems best on grounds of
+ * minimizing lock contention.)
+ *
+ * A transaction that has not yet set delayChkptFlags when we look cannot
+ * be at risk, since it has not inserted its commit record yet; and one
+ * that's already cleared it is not at risk either, since it's done fixing
+ * clog and we will correctly flush the update below. So we cannot miss
+ * any xacts we need to wait for.
+ */
+ vxids = GetVirtualXIDsDelayingChkpt(&nvxids, DELAY_CHKPT_START);
+ if (nvxids > 0)
+ {
+ do
+ {
+ pg_usleep(10000L); /* wait for 10 msec */
+ } while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,
+ DELAY_CHKPT_START));
+ }
+ pfree(vxids);
+
+ CheckPointGuts(checkPoint.redo, flags);
+
+ vxids = GetVirtualXIDsDelayingChkpt(&nvxids, DELAY_CHKPT_COMPLETE);
+ if (nvxids > 0)
+ {
+ do
+ {
+ pg_usleep(10000L); /* wait for 10 msec */
+ } while (HaveVirtualXIDsDelayingChkpt(vxids, nvxids,
+ DELAY_CHKPT_COMPLETE));
+ }
+ pfree(vxids);
+
+ /*
+ * Take a snapshot of running transactions and write this to WAL. This
+ * allows us to reconstruct the state of running transactions during
+ * archive recovery, if required. Skip, if this info disabled.
+ *
+ * If we are shutting down, or Startup process is completing crash
+ * recovery we don't need to write running xact data.
+ */
+ if (!shutdown && XLogStandbyInfoActive())
+ LogStandbySnapshot();
+
+ START_CRIT_SECTION();
+
+ /*
+ * Now insert the checkpoint record into XLOG.
+ */
+ XLogBeginInsert();
+ XLogRegisterData((char *) (&checkPoint), sizeof(checkPoint));
+ recptr = XLogInsert(RM_XLOG_ID,
+ shutdown ? XLOG_CHECKPOINT_SHUTDOWN :
+ XLOG_CHECKPOINT_ONLINE);
+
+ XLogFlush(recptr);
+
+ /*
+ * We mustn't write any new WAL after a shutdown checkpoint, or it will be
+ * overwritten at next startup. No-one should even try, this just allows
+ * sanity-checking. In the case of an end-of-recovery checkpoint, we want
+ * to just temporarily disable writing until the system has exited
+ * recovery.
+ */
+ if (shutdown)
+ {
+ if (flags & CHECKPOINT_END_OF_RECOVERY)
+ LocalXLogInsertAllowed = oldXLogAllowed;
+ else
+ LocalXLogInsertAllowed = 0; /* never again write WAL */
+ }
+
+ /*
+ * We now have ProcLastRecPtr = start of actual checkpoint record, recptr
+ * = end of actual checkpoint record.
+ */
+ if (shutdown && checkPoint.redo != ProcLastRecPtr)
+ ereport(PANIC,
+ (errmsg("concurrent write-ahead log activity while database system is shutting down")));
+
+ /*
+ * Remember the prior checkpoint's redo ptr for
+ * UpdateCheckPointDistanceEstimate()
+ */
+ PriorRedoPtr = ControlFile->checkPointCopy.redo;
+
+ /*
+ * Update the control file.
+ */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ if (shutdown)
+ ControlFile->state = DB_SHUTDOWNED;
+ ControlFile->checkPoint = ProcLastRecPtr;
+ ControlFile->checkPointCopy = checkPoint;
+ /* crash recovery should always recover to the end of WAL */
+ ControlFile->minRecoveryPoint = InvalidXLogRecPtr;
+ ControlFile->minRecoveryPointTLI = 0;
+
+ /*
+ * Persist unloggedLSN value. It's reset on crash recovery, so this goes
+ * unused on non-shutdown checkpoints, but seems useful to store it always
+ * for debugging purposes.
+ */
+ SpinLockAcquire(&XLogCtl->ulsn_lck);
+ ControlFile->unloggedLSN = XLogCtl->unloggedLSN;
+ SpinLockRelease(&XLogCtl->ulsn_lck);
+
+ UpdateControlFile();
+ LWLockRelease(ControlFileLock);
+
+ /* Update shared-memory copy of checkpoint XID/epoch */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->ckptFullXid = checkPoint.nextXid;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * We are now done with critical updates; no need for system panic if we
+ * have trouble while fooling with old log segments.
+ */
+ END_CRIT_SECTION();
+
+ /*
+ * Let smgr do post-checkpoint cleanup (eg, deleting old files).
+ */
+ SyncPostCheckpoint();
+
+ /*
+ * Update the average distance between checkpoints if the prior checkpoint
+ * exists.
+ */
+ if (PriorRedoPtr != InvalidXLogRecPtr)
+ UpdateCheckPointDistanceEstimate(RedoRecPtr - PriorRedoPtr);
+
+ /*
+ * Delete old log files, those no longer needed for last checkpoint to
+ * prevent the disk holding the xlog from growing full.
+ */
+ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size);
+ KeepLogSeg(recptr, &_logSegNo);
+ if (InvalidateObsoleteReplicationSlots(_logSegNo))
+ {
+ /*
+ * Some slots have been invalidated; recalculate the old-segment
+ * horizon, starting again from RedoRecPtr.
+ */
+ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size);
+ KeepLogSeg(recptr, &_logSegNo);
+ }
+ _logSegNo--;
+ RemoveOldXlogFiles(_logSegNo, RedoRecPtr, recptr,
+ checkPoint.ThisTimeLineID);
+
+ /*
+ * Make more log segments if needed. (Do this after recycling old log
+ * segments, since that may supply some of the needed files.)
+ */
+ if (!shutdown)
+ PreallocXlogFiles(recptr, checkPoint.ThisTimeLineID);
+
+ /*
+ * Truncate pg_subtrans if possible. We can throw away all data before
+ * the oldest XMIN of any running transaction. No future transaction will
+ * attempt to reference any pg_subtrans entry older than that (see Asserts
+ * in subtrans.c). During recovery, though, we mustn't do this because
+ * StartupSUBTRANS hasn't been called yet.
+ */
+ if (!RecoveryInProgress())
+ TruncateSUBTRANS(GetOldestTransactionIdConsideredRunning());
+
+ /* Real work is done; log and update stats. */
+ LogCheckpointEnd(false);
+
+ /* Reset the process title */
+ update_checkpoint_display(flags, false, true);
+
+ TRACE_POSTGRESQL_CHECKPOINT_DONE(CheckpointStats.ckpt_bufs_written,
+ NBuffers,
+ CheckpointStats.ckpt_segs_added,
+ CheckpointStats.ckpt_segs_removed,
+ CheckpointStats.ckpt_segs_recycled);
+}
+
+/*
+ * Mark the end of recovery in WAL though without running a full checkpoint.
+ * We can expect that a restartpoint is likely to be in progress as we
+ * do this, though we are unwilling to wait for it to complete.
+ *
+ * CreateRestartPoint() allows for the case where recovery may end before
+ * the restartpoint completes so there is no concern of concurrent behaviour.
+ */
+static void
+CreateEndOfRecoveryRecord(void)
+{
+ xl_end_of_recovery xlrec;
+ XLogRecPtr recptr;
+
+ /* sanity check */
+ if (!RecoveryInProgress())
+ elog(ERROR, "can only be used to end recovery");
+
+ xlrec.end_time = GetCurrentTimestamp();
+
+ WALInsertLockAcquireExclusive();
+ xlrec.ThisTimeLineID = XLogCtl->InsertTimeLineID;
+ xlrec.PrevTimeLineID = XLogCtl->PrevTimeLineID;
+ WALInsertLockRelease();
+
+ START_CRIT_SECTION();
+
+ XLogBeginInsert();
+ XLogRegisterData((char *) &xlrec, sizeof(xl_end_of_recovery));
+ recptr = XLogInsert(RM_XLOG_ID, XLOG_END_OF_RECOVERY);
+
+ XLogFlush(recptr);
+
+ /*
+ * Update the control file so that crash recovery can follow the timeline
+ * changes to this point.
+ */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->minRecoveryPoint = recptr;
+ ControlFile->minRecoveryPointTLI = xlrec.ThisTimeLineID;
+ UpdateControlFile();
+ LWLockRelease(ControlFileLock);
+
+ END_CRIT_SECTION();
+}
+
+/*
+ * Write an OVERWRITE_CONTRECORD message.
+ *
+ * When on WAL replay we expect a continuation record at the start of a page
+ * that is not there, recovery ends and WAL writing resumes at that point.
+ * But it's wrong to resume writing new WAL back at the start of the record
+ * that was broken, because downstream consumers of that WAL (physical
+ * replicas) are not prepared to "rewind". So the first action after
+ * finishing replay of all valid WAL must be to write a record of this type
+ * at the point where the contrecord was missing; to support xlogreader
+ * detecting the special case, XLP_FIRST_IS_OVERWRITE_CONTRECORD is also added
+ * to the page header where the record occurs. xlogreader has an ad-hoc
+ * mechanism to report metadata about the broken record, which is what we
+ * use here.
+ *
+ * At replay time, XLP_FIRST_IS_OVERWRITE_CONTRECORD instructs xlogreader to
+ * skip the record it was reading, and pass back the LSN of the skipped
+ * record, so that its caller can verify (on "replay" of that record) that the
+ * XLOG_OVERWRITE_CONTRECORD matches what was effectively overwritten.
+ *
+ * 'aborted_lsn' is the beginning position of the record that was incomplete.
+ * It is included in the WAL record. 'pagePtr' and 'newTLI' point to the
+ * beginning of the XLOG page where the record is to be inserted. They must
+ * match the current WAL insert position, they're passed here just so that we
+ * can verify that.
+ */
+static XLogRecPtr
+CreateOverwriteContrecordRecord(XLogRecPtr aborted_lsn, XLogRecPtr pagePtr,
+ TimeLineID newTLI)
+{
+ xl_overwrite_contrecord xlrec;
+ XLogRecPtr recptr;
+ XLogPageHeader pagehdr;
+ XLogRecPtr startPos;
+
+ /* sanity checks */
+ if (!RecoveryInProgress())
+ elog(ERROR, "can only be used at end of recovery");
+ if (pagePtr % XLOG_BLCKSZ != 0)
+ elog(ERROR, "invalid position for missing continuation record %X/%X",
+ LSN_FORMAT_ARGS(pagePtr));
+
+ /* The current WAL insert position should be right after the page header */
+ startPos = pagePtr;
+ if (XLogSegmentOffset(startPos, wal_segment_size) == 0)
+ startPos += SizeOfXLogLongPHD;
+ else
+ startPos += SizeOfXLogShortPHD;
+ recptr = GetXLogInsertRecPtr();
+ if (recptr != startPos)
+ elog(ERROR, "invalid WAL insert position %X/%X for OVERWRITE_CONTRECORD",
+ LSN_FORMAT_ARGS(recptr));
+
+ START_CRIT_SECTION();
+
+ /*
+ * Initialize the XLOG page header (by GetXLogBuffer), and set the
+ * XLP_FIRST_IS_OVERWRITE_CONTRECORD flag.
+ *
+ * No other backend is allowed to write WAL yet, so acquiring the WAL
+ * insertion lock is just pro forma.
+ */
+ WALInsertLockAcquire();
+ pagehdr = (XLogPageHeader) GetXLogBuffer(pagePtr, newTLI);
+ pagehdr->xlp_info |= XLP_FIRST_IS_OVERWRITE_CONTRECORD;
+ WALInsertLockRelease();
+
+ /*
+ * Insert the XLOG_OVERWRITE_CONTRECORD record as the first record on the
+ * page. We know it becomes the first record, because no other backend is
+ * allowed to write WAL yet.
+ */
+ XLogBeginInsert();
+ xlrec.overwritten_lsn = aborted_lsn;
+ xlrec.overwrite_time = GetCurrentTimestamp();
+ XLogRegisterData((char *) &xlrec, sizeof(xl_overwrite_contrecord));
+ recptr = XLogInsert(RM_XLOG_ID, XLOG_OVERWRITE_CONTRECORD);
+
+ /* check that the record was inserted to the right place */
+ if (ProcLastRecPtr != startPos)
+ elog(ERROR, "OVERWRITE_CONTRECORD was inserted to unexpected position %X/%X",
+ LSN_FORMAT_ARGS(ProcLastRecPtr));
+
+ XLogFlush(recptr);
+
+ END_CRIT_SECTION();
+
+ return recptr;
+}
+
+/*
+ * Flush all data in shared memory to disk, and fsync
+ *
+ * This is the common code shared between regular checkpoints and
+ * recovery restartpoints.
+ */
+static void
+CheckPointGuts(XLogRecPtr checkPointRedo, int flags)
+{
+ CheckPointRelationMap();
+ CheckPointReplicationSlots();
+ CheckPointSnapBuild();
+ CheckPointLogicalRewriteHeap();
+ CheckPointReplicationOrigin();
+
+ /* Write out all dirty data in SLRUs and the main buffer pool */
+ TRACE_POSTGRESQL_BUFFER_CHECKPOINT_START(flags);
+ CheckpointStats.ckpt_write_t = GetCurrentTimestamp();
+ CheckPointCLOG();
+ CheckPointCommitTs();
+ CheckPointSUBTRANS();
+ CheckPointMultiXact();
+ CheckPointPredicate();
+ CheckPointBuffers(flags);
+
+ /* Perform all queued up fsyncs */
+ TRACE_POSTGRESQL_BUFFER_CHECKPOINT_SYNC_START();
+ CheckpointStats.ckpt_sync_t = GetCurrentTimestamp();
+ ProcessSyncRequests();
+ CheckpointStats.ckpt_sync_end_t = GetCurrentTimestamp();
+ TRACE_POSTGRESQL_BUFFER_CHECKPOINT_DONE();
+
+ /* We deliberately delay 2PC checkpointing as long as possible */
+ CheckPointTwoPhase(checkPointRedo);
+}
+
+/*
+ * Save a checkpoint for recovery restart if appropriate
+ *
+ * This function is called each time a checkpoint record is read from XLOG.
+ * It must determine whether the checkpoint represents a safe restartpoint or
+ * not. If so, the checkpoint record is stashed in shared memory so that
+ * CreateRestartPoint can consult it. (Note that the latter function is
+ * executed by the checkpointer, while this one will be executed by the
+ * startup process.)
+ */
+static void
+RecoveryRestartPoint(const CheckPoint *checkPoint, XLogReaderState *record)
+{
+ /*
+ * Also refrain from creating a restartpoint if we have seen any
+ * references to non-existent pages. Restarting recovery from the
+ * restartpoint would not see the references, so we would lose the
+ * cross-check that the pages belonged to a relation that was dropped
+ * later.
+ */
+ if (XLogHaveInvalidPages())
+ {
+ elog(trace_recovery(DEBUG2),
+ "could not record restart point at %X/%X because there "
+ "are unresolved references to invalid pages",
+ LSN_FORMAT_ARGS(checkPoint->redo));
+ return;
+ }
+
+ /*
+ * Copy the checkpoint record to shared memory, so that checkpointer can
+ * work out the next time it wants to perform a restartpoint.
+ */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->lastCheckPointRecPtr = record->ReadRecPtr;
+ XLogCtl->lastCheckPointEndPtr = record->EndRecPtr;
+ XLogCtl->lastCheckPoint = *checkPoint;
+ SpinLockRelease(&XLogCtl->info_lck);
+}
+
+/*
+ * Establish a restartpoint if possible.
+ *
+ * This is similar to CreateCheckPoint, but is used during WAL recovery
+ * to establish a point from which recovery can roll forward without
+ * replaying the entire recovery log.
+ *
+ * Returns true if a new restartpoint was established. We can only establish
+ * a restartpoint if we have replayed a safe checkpoint record since last
+ * restartpoint.
+ */
+bool
+CreateRestartPoint(int flags)
+{
+ XLogRecPtr lastCheckPointRecPtr;
+ XLogRecPtr lastCheckPointEndPtr;
+ CheckPoint lastCheckPoint;
+ XLogRecPtr PriorRedoPtr;
+ XLogRecPtr receivePtr;
+ XLogRecPtr replayPtr;
+ TimeLineID replayTLI;
+ XLogRecPtr endptr;
+ XLogSegNo _logSegNo;
+ TimestampTz xtime;
+
+ /* Concurrent checkpoint/restartpoint cannot happen */
+ Assert(!IsUnderPostmaster || MyBackendType == B_CHECKPOINTER);
+
+ /* Get a local copy of the last safe checkpoint record. */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ lastCheckPointRecPtr = XLogCtl->lastCheckPointRecPtr;
+ lastCheckPointEndPtr = XLogCtl->lastCheckPointEndPtr;
+ lastCheckPoint = XLogCtl->lastCheckPoint;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * Check that we're still in recovery mode. It's ok if we exit recovery
+ * mode after this check, the restart point is valid anyway.
+ */
+ if (!RecoveryInProgress())
+ {
+ ereport(DEBUG2,
+ (errmsg_internal("skipping restartpoint, recovery has already ended")));
+ return false;
+ }
+
+ /*
+ * If the last checkpoint record we've replayed is already our last
+ * restartpoint, we can't perform a new restart point. We still update
+ * minRecoveryPoint in that case, so that if this is a shutdown restart
+ * point, we won't start up earlier than before. That's not strictly
+ * necessary, but when hot standby is enabled, it would be rather weird if
+ * the database opened up for read-only connections at a point-in-time
+ * before the last shutdown. Such time travel is still possible in case of
+ * immediate shutdown, though.
+ *
+ * We don't explicitly advance minRecoveryPoint when we do create a
+ * restartpoint. It's assumed that flushing the buffers will do that as a
+ * side-effect.
+ */
+ if (XLogRecPtrIsInvalid(lastCheckPointRecPtr) ||
+ lastCheckPoint.redo <= ControlFile->checkPointCopy.redo)
+ {
+ ereport(DEBUG2,
+ (errmsg_internal("skipping restartpoint, already performed at %X/%X",
+ LSN_FORMAT_ARGS(lastCheckPoint.redo))));
+
+ UpdateMinRecoveryPoint(InvalidXLogRecPtr, true);
+ if (flags & CHECKPOINT_IS_SHUTDOWN)
+ {
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY;
+ UpdateControlFile();
+ LWLockRelease(ControlFileLock);
+ }
+ return false;
+ }
+
+ /*
+ * Update the shared RedoRecPtr so that the startup process can calculate
+ * the number of segments replayed since last restartpoint, and request a
+ * restartpoint if it exceeds CheckPointSegments.
+ *
+ * Like in CreateCheckPoint(), hold off insertions to update it, although
+ * during recovery this is just pro forma, because no WAL insertions are
+ * happening.
+ */
+ WALInsertLockAcquireExclusive();
+ RedoRecPtr = XLogCtl->Insert.RedoRecPtr = lastCheckPoint.redo;
+ WALInsertLockRelease();
+
+ /* Also update the info_lck-protected copy */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->RedoRecPtr = lastCheckPoint.redo;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * Prepare to accumulate statistics.
+ *
+ * Note: because it is possible for log_checkpoints to change while a
+ * checkpoint proceeds, we always accumulate stats, even if
+ * log_checkpoints is currently off.
+ */
+ MemSet(&CheckpointStats, 0, sizeof(CheckpointStats));
+ CheckpointStats.ckpt_start_t = GetCurrentTimestamp();
+
+ if (log_checkpoints)
+ LogCheckpointStart(flags, true);
+
+ /* Update the process title */
+ update_checkpoint_display(flags, true, false);
+
+ CheckPointGuts(lastCheckPoint.redo, flags);
+
+ /*
+ * Remember the prior checkpoint's redo ptr for
+ * UpdateCheckPointDistanceEstimate()
+ */
+ PriorRedoPtr = ControlFile->checkPointCopy.redo;
+
+ /*
+ * Update pg_control, using current time. Check that it still shows an
+ * older checkpoint, else do nothing; this is a quick hack to make sure
+ * nothing really bad happens if somehow we get here after the
+ * end-of-recovery checkpoint.
+ */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ if (ControlFile->checkPointCopy.redo < lastCheckPoint.redo)
+ {
+ /*
+ * Update the checkpoint information. We do this even if the cluster
+ * does not show DB_IN_ARCHIVE_RECOVERY to match with the set of WAL
+ * segments recycled below.
+ */
+ ControlFile->checkPoint = lastCheckPointRecPtr;
+ ControlFile->checkPointCopy = lastCheckPoint;
+
+ /*
+ * Ensure minRecoveryPoint is past the checkpoint record and update it
+ * if the control file still shows DB_IN_ARCHIVE_RECOVERY. Normally,
+ * this will have happened already while writing out dirty buffers,
+ * but not necessarily - e.g. because no buffers were dirtied. We do
+ * this because a backup performed in recovery uses minRecoveryPoint
+ * to determine which WAL files must be included in the backup, and
+ * the file (or files) containing the checkpoint record must be
+ * included, at a minimum. Note that for an ordinary restart of
+ * recovery there's no value in having the minimum recovery point any
+ * earlier than this anyway, because redo will begin just after the
+ * checkpoint record.
+ */
+ if (ControlFile->state == DB_IN_ARCHIVE_RECOVERY)
+ {
+ if (ControlFile->minRecoveryPoint < lastCheckPointEndPtr)
+ {
+ ControlFile->minRecoveryPoint = lastCheckPointEndPtr;
+ ControlFile->minRecoveryPointTLI = lastCheckPoint.ThisTimeLineID;
+
+ /* update local copy */
+ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint;
+ LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
+ }
+ if (flags & CHECKPOINT_IS_SHUTDOWN)
+ ControlFile->state = DB_SHUTDOWNED_IN_RECOVERY;
+ }
+ UpdateControlFile();
+ }
+ LWLockRelease(ControlFileLock);
+
+ /*
+ * Update the average distance between checkpoints/restartpoints if the
+ * prior checkpoint exists.
+ */
+ if (PriorRedoPtr != InvalidXLogRecPtr)
+ UpdateCheckPointDistanceEstimate(RedoRecPtr - PriorRedoPtr);
+
+ /*
+ * Delete old log files, those no longer needed for last restartpoint to
+ * prevent the disk holding the xlog from growing full.
+ */
+ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size);
+
+ /*
+ * Retreat _logSegNo using the current end of xlog replayed or received,
+ * whichever is later.
+ */
+ receivePtr = GetWalRcvFlushRecPtr(NULL, NULL);
+ replayPtr = GetXLogReplayRecPtr(&replayTLI);
+ endptr = (receivePtr < replayPtr) ? replayPtr : receivePtr;
+ KeepLogSeg(endptr, &_logSegNo);
+ if (InvalidateObsoleteReplicationSlots(_logSegNo))
+ {
+ /*
+ * Some slots have been invalidated; recalculate the old-segment
+ * horizon, starting again from RedoRecPtr.
+ */
+ XLByteToSeg(RedoRecPtr, _logSegNo, wal_segment_size);
+ KeepLogSeg(endptr, &_logSegNo);
+ }
+ _logSegNo--;
+
+ /*
+ * Try to recycle segments on a useful timeline. If we've been promoted
+ * since the beginning of this restartpoint, use the new timeline chosen
+ * at end of recovery. If we're still in recovery, use the timeline we're
+ * currently replaying.
+ *
+ * There is no guarantee that the WAL segments will be useful on the
+ * current timeline; if recovery proceeds to a new timeline right after
+ * this, the pre-allocated WAL segments on this timeline will not be used,
+ * and will go wasted until recycled on the next restartpoint. We'll live
+ * with that.
+ */
+ if (!RecoveryInProgress())
+ replayTLI = XLogCtl->InsertTimeLineID;
+
+ RemoveOldXlogFiles(_logSegNo, RedoRecPtr, endptr, replayTLI);
+
+ /*
+ * Make more log segments if needed. (Do this after recycling old log
+ * segments, since that may supply some of the needed files.)
+ */
+ PreallocXlogFiles(endptr, replayTLI);
+
+ /*
+ * Truncate pg_subtrans if possible. We can throw away all data before
+ * the oldest XMIN of any running transaction. No future transaction will
+ * attempt to reference any pg_subtrans entry older than that (see Asserts
+ * in subtrans.c). When hot standby is disabled, though, we mustn't do
+ * this because StartupSUBTRANS hasn't been called yet.
+ */
+ if (EnableHotStandby)
+ TruncateSUBTRANS(GetOldestTransactionIdConsideredRunning());
+
+ /* Real work is done; log and update stats. */
+ LogCheckpointEnd(true);
+
+ /* Reset the process title */
+ update_checkpoint_display(flags, true, true);
+
+ xtime = GetLatestXTime();
+ ereport((log_checkpoints ? LOG : DEBUG2),
+ (errmsg("recovery restart point at %X/%X",
+ LSN_FORMAT_ARGS(lastCheckPoint.redo)),
+ xtime ? errdetail("Last completed transaction was at log time %s.",
+ timestamptz_to_str(xtime)) : 0));
+
+ /*
+ * Finally, execute archive_cleanup_command, if any.
+ */
+ if (archiveCleanupCommand && strcmp(archiveCleanupCommand, "") != 0)
+ ExecuteRecoveryCommand(archiveCleanupCommand,
+ "archive_cleanup_command",
+ false,
+ WAIT_EVENT_ARCHIVE_CLEANUP_COMMAND);
+
+ return true;
+}
+
+/*
+ * Report availability of WAL for the given target LSN
+ * (typically a slot's restart_lsn)
+ *
+ * Returns one of the following enum values:
+ *
+ * * WALAVAIL_RESERVED means targetLSN is available and it is in the range of
+ * max_wal_size.
+ *
+ * * WALAVAIL_EXTENDED means it is still available by preserving extra
+ * segments beyond max_wal_size. If max_slot_wal_keep_size is smaller
+ * than max_wal_size, this state is not returned.
+ *
+ * * WALAVAIL_UNRESERVED means it is being lost and the next checkpoint will
+ * remove reserved segments. The walsender using this slot may return to the
+ * above.
+ *
+ * * WALAVAIL_REMOVED means it has been removed. A replication stream on
+ * a slot with this LSN cannot continue after a restart.
+ *
+ * * WALAVAIL_INVALID_LSN means the slot hasn't been set to reserve WAL.
+ */
+WALAvailability
+GetWALAvailability(XLogRecPtr targetLSN)
+{
+ XLogRecPtr currpos; /* current write LSN */
+ XLogSegNo currSeg; /* segid of currpos */
+ XLogSegNo targetSeg; /* segid of targetLSN */
+ XLogSegNo oldestSeg; /* actual oldest segid */
+ XLogSegNo oldestSegMaxWalSize; /* oldest segid kept by max_wal_size */
+ XLogSegNo oldestSlotSeg; /* oldest segid kept by slot */
+ uint64 keepSegs;
+
+ /*
+ * slot does not reserve WAL. Either deactivated, or has never been active
+ */
+ if (XLogRecPtrIsInvalid(targetLSN))
+ return WALAVAIL_INVALID_LSN;
+
+ /*
+ * Calculate the oldest segment currently reserved by all slots,
+ * considering wal_keep_size and max_slot_wal_keep_size. Initialize
+ * oldestSlotSeg to the current segment.
+ */
+ currpos = GetXLogWriteRecPtr();
+ XLByteToSeg(currpos, oldestSlotSeg, wal_segment_size);
+ KeepLogSeg(currpos, &oldestSlotSeg);
+
+ /*
+ * Find the oldest extant segment file. We get 1 until checkpoint removes
+ * the first WAL segment file since startup, which causes the status being
+ * wrong under certain abnormal conditions but that doesn't actually harm.
+ */
+ oldestSeg = XLogGetLastRemovedSegno() + 1;
+
+ /* calculate oldest segment by max_wal_size */
+ XLByteToSeg(currpos, currSeg, wal_segment_size);
+ keepSegs = ConvertToXSegs(max_wal_size_mb, wal_segment_size) + 1;
+
+ if (currSeg > keepSegs)
+ oldestSegMaxWalSize = currSeg - keepSegs;
+ else
+ oldestSegMaxWalSize = 1;
+
+ /* the segment we care about */
+ XLByteToSeg(targetLSN, targetSeg, wal_segment_size);
+
+ /*
+ * No point in returning reserved or extended status values if the
+ * targetSeg is known to be lost.
+ */
+ if (targetSeg >= oldestSlotSeg)
+ {
+ /* show "reserved" when targetSeg is within max_wal_size */
+ if (targetSeg >= oldestSegMaxWalSize)
+ return WALAVAIL_RESERVED;
+
+ /* being retained by slots exceeding max_wal_size */
+ return WALAVAIL_EXTENDED;
+ }
+
+ /* WAL segments are no longer retained but haven't been removed yet */
+ if (targetSeg >= oldestSeg)
+ return WALAVAIL_UNRESERVED;
+
+ /* Definitely lost */
+ return WALAVAIL_REMOVED;
+}
+
+
+/*
+ * Retreat *logSegNo to the last segment that we need to retain because of
+ * either wal_keep_size or replication slots.
+ *
+ * This is calculated by subtracting wal_keep_size from the given xlog
+ * location, recptr and by making sure that that result is below the
+ * requirement of replication slots. For the latter criterion we do consider
+ * the effects of max_slot_wal_keep_size: reserve at most that much space back
+ * from recptr.
+ *
+ * Note about replication slots: if this function calculates a value
+ * that's further ahead than what slots need reserved, then affected
+ * slots need to be invalidated and this function invoked again.
+ * XXX it might be a good idea to rewrite this function so that
+ * invalidation is optionally done here, instead.
+ */
+static void
+KeepLogSeg(XLogRecPtr recptr, XLogSegNo *logSegNo)
+{
+ XLogSegNo currSegNo;
+ XLogSegNo segno;
+ XLogRecPtr keep;
+
+ XLByteToSeg(recptr, currSegNo, wal_segment_size);
+ segno = currSegNo;
+
+ /*
+ * Calculate how many segments are kept by slots first, adjusting for
+ * max_slot_wal_keep_size.
+ */
+ keep = XLogGetReplicationSlotMinimumLSN();
+ if (keep != InvalidXLogRecPtr && keep < recptr)
+ {
+ XLByteToSeg(keep, segno, wal_segment_size);
+
+ /* Cap by max_slot_wal_keep_size ... */
+ if (max_slot_wal_keep_size_mb >= 0)
+ {
+ uint64 slot_keep_segs;
+
+ slot_keep_segs =
+ ConvertToXSegs(max_slot_wal_keep_size_mb, wal_segment_size);
+
+ if (currSegNo - segno > slot_keep_segs)
+ segno = currSegNo - slot_keep_segs;
+ }
+ }
+
+ /* but, keep at least wal_keep_size if that's set */
+ if (wal_keep_size_mb > 0)
+ {
+ uint64 keep_segs;
+
+ keep_segs = ConvertToXSegs(wal_keep_size_mb, wal_segment_size);
+ if (currSegNo - segno < keep_segs)
+ {
+ /* avoid underflow, don't go below 1 */
+ if (currSegNo <= keep_segs)
+ segno = 1;
+ else
+ segno = currSegNo - keep_segs;
+ }
+ }
+
+ /* don't delete WAL segments newer than the calculated segment */
+ if (segno < *logSegNo)
+ *logSegNo = segno;
+}
+
+/*
+ * Write a NEXTOID log record
+ */
+void
+XLogPutNextOid(Oid nextOid)
+{
+ XLogBeginInsert();
+ XLogRegisterData((char *) (&nextOid), sizeof(Oid));
+ (void) XLogInsert(RM_XLOG_ID, XLOG_NEXTOID);
+
+ /*
+ * We need not flush the NEXTOID record immediately, because any of the
+ * just-allocated OIDs could only reach disk as part of a tuple insert or
+ * update that would have its own XLOG record that must follow the NEXTOID
+ * record. Therefore, the standard buffer LSN interlock applied to those
+ * records will ensure no such OID reaches disk before the NEXTOID record
+ * does.
+ *
+ * Note, however, that the above statement only covers state "within" the
+ * database. When we use a generated OID as a file or directory name, we
+ * are in a sense violating the basic WAL rule, because that filesystem
+ * change may reach disk before the NEXTOID WAL record does. The impact
+ * of this is that if a database crash occurs immediately afterward, we
+ * might after restart re-generate the same OID and find that it conflicts
+ * with the leftover file or directory. But since for safety's sake we
+ * always loop until finding a nonconflicting filename, this poses no real
+ * problem in practice. See pgsql-hackers discussion 27-Sep-2006.
+ */
+}
+
+/*
+ * Write an XLOG SWITCH record.
+ *
+ * Here we just blindly issue an XLogInsert request for the record.
+ * All the magic happens inside XLogInsert.
+ *
+ * The return value is either the end+1 address of the switch record,
+ * or the end+1 address of the prior segment if we did not need to
+ * write a switch record because we are already at segment start.
+ */
+XLogRecPtr
+RequestXLogSwitch(bool mark_unimportant)
+{
+ XLogRecPtr RecPtr;
+
+ /* XLOG SWITCH has no data */
+ XLogBeginInsert();
+
+ if (mark_unimportant)
+ XLogSetRecordFlags(XLOG_MARK_UNIMPORTANT);
+ RecPtr = XLogInsert(RM_XLOG_ID, XLOG_SWITCH);
+
+ return RecPtr;
+}
+
+/*
+ * Write a RESTORE POINT record
+ */
+XLogRecPtr
+XLogRestorePoint(const char *rpName)
+{
+ XLogRecPtr RecPtr;
+ xl_restore_point xlrec;
+
+ xlrec.rp_time = GetCurrentTimestamp();
+ strlcpy(xlrec.rp_name, rpName, MAXFNAMELEN);
+
+ XLogBeginInsert();
+ XLogRegisterData((char *) &xlrec, sizeof(xl_restore_point));
+
+ RecPtr = XLogInsert(RM_XLOG_ID, XLOG_RESTORE_POINT);
+
+ ereport(LOG,
+ (errmsg("restore point \"%s\" created at %X/%X",
+ rpName, LSN_FORMAT_ARGS(RecPtr))));
+
+ return RecPtr;
+}
+
+/*
+ * Check if any of the GUC parameters that are critical for hot standby
+ * have changed, and update the value in pg_control file if necessary.
+ */
+static void
+XLogReportParameters(void)
+{
+ if (wal_level != ControlFile->wal_level ||
+ wal_log_hints != ControlFile->wal_log_hints ||
+ MaxConnections != ControlFile->MaxConnections ||
+ max_worker_processes != ControlFile->max_worker_processes ||
+ max_wal_senders != ControlFile->max_wal_senders ||
+ max_prepared_xacts != ControlFile->max_prepared_xacts ||
+ max_locks_per_xact != ControlFile->max_locks_per_xact ||
+ track_commit_timestamp != ControlFile->track_commit_timestamp)
+ {
+ /*
+ * The change in number of backend slots doesn't need to be WAL-logged
+ * if archiving is not enabled, as you can't start archive recovery
+ * with wal_level=minimal anyway. We don't really care about the
+ * values in pg_control either if wal_level=minimal, but seems better
+ * to keep them up-to-date to avoid confusion.
+ */
+ if (wal_level != ControlFile->wal_level || XLogIsNeeded())
+ {
+ xl_parameter_change xlrec;
+ XLogRecPtr recptr;
+
+ xlrec.MaxConnections = MaxConnections;
+ xlrec.max_worker_processes = max_worker_processes;
+ xlrec.max_wal_senders = max_wal_senders;
+ xlrec.max_prepared_xacts = max_prepared_xacts;
+ xlrec.max_locks_per_xact = max_locks_per_xact;
+ xlrec.wal_level = wal_level;
+ xlrec.wal_log_hints = wal_log_hints;
+ xlrec.track_commit_timestamp = track_commit_timestamp;
+
+ XLogBeginInsert();
+ XLogRegisterData((char *) &xlrec, sizeof(xlrec));
+
+ recptr = XLogInsert(RM_XLOG_ID, XLOG_PARAMETER_CHANGE);
+ XLogFlush(recptr);
+ }
+
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+
+ ControlFile->MaxConnections = MaxConnections;
+ ControlFile->max_worker_processes = max_worker_processes;
+ ControlFile->max_wal_senders = max_wal_senders;
+ ControlFile->max_prepared_xacts = max_prepared_xacts;
+ ControlFile->max_locks_per_xact = max_locks_per_xact;
+ ControlFile->wal_level = wal_level;
+ ControlFile->wal_log_hints = wal_log_hints;
+ ControlFile->track_commit_timestamp = track_commit_timestamp;
+ UpdateControlFile();
+
+ LWLockRelease(ControlFileLock);
+ }
+}
+
+/*
+ * Update full_page_writes in shared memory, and write an
+ * XLOG_FPW_CHANGE record if necessary.
+ *
+ * Note: this function assumes there is no other process running
+ * concurrently that could update it.
+ */
+void
+UpdateFullPageWrites(void)
+{
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ bool recoveryInProgress;
+
+ /*
+ * Do nothing if full_page_writes has not been changed.
+ *
+ * It's safe to check the shared full_page_writes without the lock,
+ * because we assume that there is no concurrently running process which
+ * can update it.
+ */
+ if (fullPageWrites == Insert->fullPageWrites)
+ return;
+
+ /*
+ * Perform this outside critical section so that the WAL insert
+ * initialization done by RecoveryInProgress() doesn't trigger an
+ * assertion failure.
+ */
+ recoveryInProgress = RecoveryInProgress();
+
+ START_CRIT_SECTION();
+
+ /*
+ * It's always safe to take full page images, even when not strictly
+ * required, but not the other round. So if we're setting full_page_writes
+ * to true, first set it true and then write the WAL record. If we're
+ * setting it to false, first write the WAL record and then set the global
+ * flag.
+ */
+ if (fullPageWrites)
+ {
+ WALInsertLockAcquireExclusive();
+ Insert->fullPageWrites = true;
+ WALInsertLockRelease();
+ }
+
+ /*
+ * Write an XLOG_FPW_CHANGE record. This allows us to keep track of
+ * full_page_writes during archive recovery, if required.
+ */
+ if (XLogStandbyInfoActive() && !recoveryInProgress)
+ {
+ XLogBeginInsert();
+ XLogRegisterData((char *) (&fullPageWrites), sizeof(bool));
+
+ XLogInsert(RM_XLOG_ID, XLOG_FPW_CHANGE);
+ }
+
+ if (!fullPageWrites)
+ {
+ WALInsertLockAcquireExclusive();
+ Insert->fullPageWrites = false;
+ WALInsertLockRelease();
+ }
+ END_CRIT_SECTION();
+}
+
+/*
+ * XLOG resource manager's routines
+ *
+ * Definitions of info values are in include/catalog/pg_control.h, though
+ * not all record types are related to control file updates.
+ *
+ * NOTE: Some XLOG record types that are directly related to WAL recovery
+ * are handled in xlogrecovery_redo().
+ */
+void
+xlog_redo(XLogReaderState *record)
+{
+ uint8 info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
+ XLogRecPtr lsn = record->EndRecPtr;
+
+ /*
+ * In XLOG rmgr, backup blocks are only used by XLOG_FPI and
+ * XLOG_FPI_FOR_HINT records.
+ */
+ Assert(info == XLOG_FPI || info == XLOG_FPI_FOR_HINT ||
+ !XLogRecHasAnyBlockRefs(record));
+
+ if (info == XLOG_NEXTOID)
+ {
+ Oid nextOid;
+
+ /*
+ * We used to try to take the maximum of ShmemVariableCache->nextOid
+ * and the recorded nextOid, but that fails if the OID counter wraps
+ * around. Since no OID allocation should be happening during replay
+ * anyway, better to just believe the record exactly. We still take
+ * OidGenLock while setting the variable, just in case.
+ */
+ memcpy(&nextOid, XLogRecGetData(record), sizeof(Oid));
+ LWLockAcquire(OidGenLock, LW_EXCLUSIVE);
+ ShmemVariableCache->nextOid = nextOid;
+ ShmemVariableCache->oidCount = 0;
+ LWLockRelease(OidGenLock);
+ }
+ else if (info == XLOG_CHECKPOINT_SHUTDOWN)
+ {
+ CheckPoint checkPoint;
+ TimeLineID replayTLI;
+
+ memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint));
+ /* In a SHUTDOWN checkpoint, believe the counters exactly */
+ LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
+ ShmemVariableCache->nextXid = checkPoint.nextXid;
+ LWLockRelease(XidGenLock);
+ LWLockAcquire(OidGenLock, LW_EXCLUSIVE);
+ ShmemVariableCache->nextOid = checkPoint.nextOid;
+ ShmemVariableCache->oidCount = 0;
+ LWLockRelease(OidGenLock);
+ MultiXactSetNextMXact(checkPoint.nextMulti,
+ checkPoint.nextMultiOffset);
+
+ MultiXactAdvanceOldest(checkPoint.oldestMulti,
+ checkPoint.oldestMultiDB);
+
+ /*
+ * No need to set oldestClogXid here as well; it'll be set when we
+ * redo an xl_clog_truncate if it changed since initialization.
+ */
+ SetTransactionIdLimit(checkPoint.oldestXid, checkPoint.oldestXidDB);
+
+ /*
+ * If we see a shutdown checkpoint while waiting for an end-of-backup
+ * record, the backup was canceled and the end-of-backup record will
+ * never arrive.
+ */
+ if (ArchiveRecoveryRequested &&
+ !XLogRecPtrIsInvalid(ControlFile->backupStartPoint) &&
+ XLogRecPtrIsInvalid(ControlFile->backupEndPoint))
+ ereport(PANIC,
+ (errmsg("online backup was canceled, recovery cannot continue")));
+
+ /*
+ * If we see a shutdown checkpoint, we know that nothing was running
+ * on the primary at this point. So fake-up an empty running-xacts
+ * record and use that here and now. Recover additional standby state
+ * for prepared transactions.
+ */
+ if (standbyState >= STANDBY_INITIALIZED)
+ {
+ TransactionId *xids;
+ int nxids;
+ TransactionId oldestActiveXID;
+ TransactionId latestCompletedXid;
+ RunningTransactionsData running;
+
+ oldestActiveXID = PrescanPreparedTransactions(&xids, &nxids);
+
+ /*
+ * Construct a RunningTransactions snapshot representing a shut
+ * down server, with only prepared transactions still alive. We're
+ * never overflowed at this point because all subxids are listed
+ * with their parent prepared transactions.
+ */
+ running.xcnt = nxids;
+ running.subxcnt = 0;
+ running.subxid_overflow = false;
+ running.nextXid = XidFromFullTransactionId(checkPoint.nextXid);
+ running.oldestRunningXid = oldestActiveXID;
+ latestCompletedXid = XidFromFullTransactionId(checkPoint.nextXid);
+ TransactionIdRetreat(latestCompletedXid);
+ Assert(TransactionIdIsNormal(latestCompletedXid));
+ running.latestCompletedXid = latestCompletedXid;
+ running.xids = xids;
+
+ ProcArrayApplyRecoveryInfo(&running);
+
+ StandbyRecoverPreparedTransactions();
+ }
+
+ /* ControlFile->checkPointCopy always tracks the latest ckpt XID */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->checkPointCopy.nextXid = checkPoint.nextXid;
+ LWLockRelease(ControlFileLock);
+
+ /* Update shared-memory copy of checkpoint XID/epoch */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->ckptFullXid = checkPoint.nextXid;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /*
+ * We should've already switched to the new TLI before replaying this
+ * record.
+ */
+ (void) GetCurrentReplayRecPtr(&replayTLI);
+ if (checkPoint.ThisTimeLineID != replayTLI)
+ ereport(PANIC,
+ (errmsg("unexpected timeline ID %u (should be %u) in shutdown checkpoint record",
+ checkPoint.ThisTimeLineID, replayTLI)));
+
+ RecoveryRestartPoint(&checkPoint, record);
+ }
+ else if (info == XLOG_CHECKPOINT_ONLINE)
+ {
+ CheckPoint checkPoint;
+ TimeLineID replayTLI;
+
+ memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint));
+ /* In an ONLINE checkpoint, treat the XID counter as a minimum */
+ LWLockAcquire(XidGenLock, LW_EXCLUSIVE);
+ if (FullTransactionIdPrecedes(ShmemVariableCache->nextXid,
+ checkPoint.nextXid))
+ ShmemVariableCache->nextXid = checkPoint.nextXid;
+ LWLockRelease(XidGenLock);
+
+ /*
+ * We ignore the nextOid counter in an ONLINE checkpoint, preferring
+ * to track OID assignment through XLOG_NEXTOID records. The nextOid
+ * counter is from the start of the checkpoint and might well be stale
+ * compared to later XLOG_NEXTOID records. We could try to take the
+ * maximum of the nextOid counter and our latest value, but since
+ * there's no particular guarantee about the speed with which the OID
+ * counter wraps around, that's a risky thing to do. In any case,
+ * users of the nextOid counter are required to avoid assignment of
+ * duplicates, so that a somewhat out-of-date value should be safe.
+ */
+
+ /* Handle multixact */
+ MultiXactAdvanceNextMXact(checkPoint.nextMulti,
+ checkPoint.nextMultiOffset);
+
+ /*
+ * NB: This may perform multixact truncation when replaying WAL
+ * generated by an older primary.
+ */
+ MultiXactAdvanceOldest(checkPoint.oldestMulti,
+ checkPoint.oldestMultiDB);
+ if (TransactionIdPrecedes(ShmemVariableCache->oldestXid,
+ checkPoint.oldestXid))
+ SetTransactionIdLimit(checkPoint.oldestXid,
+ checkPoint.oldestXidDB);
+ /* ControlFile->checkPointCopy always tracks the latest ckpt XID */
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->checkPointCopy.nextXid = checkPoint.nextXid;
+ LWLockRelease(ControlFileLock);
+
+ /* Update shared-memory copy of checkpoint XID/epoch */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->ckptFullXid = checkPoint.nextXid;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ /* TLI should not change in an on-line checkpoint */
+ (void) GetCurrentReplayRecPtr(&replayTLI);
+ if (checkPoint.ThisTimeLineID != replayTLI)
+ ereport(PANIC,
+ (errmsg("unexpected timeline ID %u (should be %u) in online checkpoint record",
+ checkPoint.ThisTimeLineID, replayTLI)));
+
+ RecoveryRestartPoint(&checkPoint, record);
+ }
+ else if (info == XLOG_OVERWRITE_CONTRECORD)
+ {
+ /* nothing to do here, handled in xlogrecovery_redo() */
+ }
+ else if (info == XLOG_END_OF_RECOVERY)
+ {
+ xl_end_of_recovery xlrec;
+ TimeLineID replayTLI;
+
+ memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_end_of_recovery));
+
+ /*
+ * For Hot Standby, we could treat this like a Shutdown Checkpoint,
+ * but this case is rarer and harder to test, so the benefit doesn't
+ * outweigh the potential extra cost of maintenance.
+ */
+
+ /*
+ * We should've already switched to the new TLI before replaying this
+ * record.
+ */
+ (void) GetCurrentReplayRecPtr(&replayTLI);
+ if (xlrec.ThisTimeLineID != replayTLI)
+ ereport(PANIC,
+ (errmsg("unexpected timeline ID %u (should be %u) in end-of-recovery record",
+ xlrec.ThisTimeLineID, replayTLI)));
+ }
+ else if (info == XLOG_NOOP)
+ {
+ /* nothing to do here */
+ }
+ else if (info == XLOG_SWITCH)
+ {
+ /* nothing to do here */
+ }
+ else if (info == XLOG_RESTORE_POINT)
+ {
+ /* nothing to do here, handled in xlogrecovery.c */
+ }
+ else if (info == XLOG_FPI || info == XLOG_FPI_FOR_HINT)
+ {
+ /*
+ * XLOG_FPI records contain nothing else but one or more block
+ * references. Every block reference must include a full-page image
+ * even if full_page_writes was disabled when the record was generated
+ * - otherwise there would be no point in this record.
+ *
+ * XLOG_FPI_FOR_HINT records are generated when a page needs to be
+ * WAL-logged because of a hint bit update. They are only generated
+ * when checksums and/or wal_log_hints are enabled. They may include
+ * no full-page images if full_page_writes was disabled when they were
+ * generated. In this case there is nothing to do here.
+ *
+ * No recovery conflicts are generated by these generic records - if a
+ * resource manager needs to generate conflicts, it has to define a
+ * separate WAL record type and redo routine.
+ */
+ for (uint8 block_id = 0; block_id <= XLogRecMaxBlockId(record); block_id++)
+ {
+ Buffer buffer;
+
+ if (!XLogRecHasBlockImage(record, block_id))
+ {
+ if (info == XLOG_FPI)
+ elog(ERROR, "XLOG_FPI record did not contain a full-page image");
+ continue;
+ }
+
+ if (XLogReadBufferForRedo(record, block_id, &buffer) != BLK_RESTORED)
+ elog(ERROR, "unexpected XLogReadBufferForRedo result when restoring backup block");
+ UnlockReleaseBuffer(buffer);
+ }
+ }
+ else if (info == XLOG_BACKUP_END)
+ {
+ /* nothing to do here, handled in xlogrecovery_redo() */
+ }
+ else if (info == XLOG_PARAMETER_CHANGE)
+ {
+ xl_parameter_change xlrec;
+
+ /* Update our copy of the parameters in pg_control */
+ memcpy(&xlrec, XLogRecGetData(record), sizeof(xl_parameter_change));
+
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ ControlFile->MaxConnections = xlrec.MaxConnections;
+ ControlFile->max_worker_processes = xlrec.max_worker_processes;
+ ControlFile->max_wal_senders = xlrec.max_wal_senders;
+ ControlFile->max_prepared_xacts = xlrec.max_prepared_xacts;
+ ControlFile->max_locks_per_xact = xlrec.max_locks_per_xact;
+ ControlFile->wal_level = xlrec.wal_level;
+ ControlFile->wal_log_hints = xlrec.wal_log_hints;
+
+ /*
+ * Update minRecoveryPoint to ensure that if recovery is aborted, we
+ * recover back up to this point before allowing hot standby again.
+ * This is important if the max_* settings are decreased, to ensure
+ * you don't run queries against the WAL preceding the change. The
+ * local copies cannot be updated as long as crash recovery is
+ * happening and we expect all the WAL to be replayed.
+ */
+ if (InArchiveRecovery)
+ {
+ LocalMinRecoveryPoint = ControlFile->minRecoveryPoint;
+ LocalMinRecoveryPointTLI = ControlFile->minRecoveryPointTLI;
+ }
+ if (LocalMinRecoveryPoint != InvalidXLogRecPtr && LocalMinRecoveryPoint < lsn)
+ {
+ TimeLineID replayTLI;
+
+ (void) GetCurrentReplayRecPtr(&replayTLI);
+ ControlFile->minRecoveryPoint = lsn;
+ ControlFile->minRecoveryPointTLI = replayTLI;
+ }
+
+ CommitTsParameterChange(xlrec.track_commit_timestamp,
+ ControlFile->track_commit_timestamp);
+ ControlFile->track_commit_timestamp = xlrec.track_commit_timestamp;
+
+ UpdateControlFile();
+ LWLockRelease(ControlFileLock);
+
+ /* Check to see if any parameter change gives a problem on recovery */
+ CheckRequiredParameterValues();
+ }
+ else if (info == XLOG_FPW_CHANGE)
+ {
+ bool fpw;
+
+ memcpy(&fpw, XLogRecGetData(record), sizeof(bool));
+
+ /*
+ * Update the LSN of the last replayed XLOG_FPW_CHANGE record so that
+ * do_pg_backup_start() and do_pg_backup_stop() can check whether
+ * full_page_writes has been disabled during online backup.
+ */
+ if (!fpw)
+ {
+ SpinLockAcquire(&XLogCtl->info_lck);
+ if (XLogCtl->lastFpwDisableRecPtr < record->ReadRecPtr)
+ XLogCtl->lastFpwDisableRecPtr = record->ReadRecPtr;
+ SpinLockRelease(&XLogCtl->info_lck);
+ }
+
+ /* Keep track of full_page_writes */
+ lastFullPageWrites = fpw;
+ }
+}
+
+/*
+ * Return the (possible) sync flag used for opening a file, depending on the
+ * value of the GUC wal_sync_method.
+ */
+static int
+get_sync_bit(int method)
+{
+ int o_direct_flag = 0;
+
+ /* If fsync is disabled, never open in sync mode */
+ if (!enableFsync)
+ return 0;
+
+ /*
+ * Optimize writes by bypassing kernel cache with O_DIRECT when using
+ * O_SYNC/O_FSYNC and O_DSYNC. But only if archiving and streaming are
+ * disabled, otherwise the archive command or walsender process will read
+ * the WAL soon after writing it, which is guaranteed to cause a physical
+ * read if we bypassed the kernel cache. We also skip the
+ * posix_fadvise(POSIX_FADV_DONTNEED) call in XLogFileClose() for the same
+ * reason.
+ *
+ * Never use O_DIRECT in walreceiver process for similar reasons; the WAL
+ * written by walreceiver is normally read by the startup process soon
+ * after it's written. Also, walreceiver performs unaligned writes, which
+ * don't work with O_DIRECT, so it is required for correctness too.
+ */
+ if (!XLogIsNeeded() && !AmWalReceiverProcess())
+ o_direct_flag = PG_O_DIRECT;
+
+ switch (method)
+ {
+ /*
+ * enum values for all sync options are defined even if they are
+ * not supported on the current platform. But if not, they are
+ * not included in the enum option array, and therefore will never
+ * be seen here.
+ */
+ case SYNC_METHOD_FSYNC:
+ case SYNC_METHOD_FSYNC_WRITETHROUGH:
+ case SYNC_METHOD_FDATASYNC:
+ return 0;
+#ifdef OPEN_SYNC_FLAG
+ case SYNC_METHOD_OPEN:
+ return OPEN_SYNC_FLAG | o_direct_flag;
+#endif
+#ifdef OPEN_DATASYNC_FLAG
+ case SYNC_METHOD_OPEN_DSYNC:
+ return OPEN_DATASYNC_FLAG | o_direct_flag;
+#endif
+ default:
+ /* can't happen (unless we are out of sync with option array) */
+ elog(ERROR, "unrecognized wal_sync_method: %d", method);
+ return 0; /* silence warning */
+ }
+}
+
+/*
+ * GUC support
+ */
+void
+assign_xlog_sync_method(int new_sync_method, void *extra)
+{
+ if (sync_method != new_sync_method)
+ {
+ /*
+ * To ensure that no blocks escape unsynced, force an fsync on the
+ * currently open log segment (if any). Also, if the open flag is
+ * changing, close the log file so it will be reopened (with new flag
+ * bit) at next use.
+ */
+ if (openLogFile >= 0)
+ {
+ pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN);
+ if (pg_fsync(openLogFile) != 0)
+ {
+ char xlogfname[MAXFNAMELEN];
+ int save_errno;
+
+ save_errno = errno;
+ XLogFileName(xlogfname, openLogTLI, openLogSegNo,
+ wal_segment_size);
+ errno = save_errno;
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg("could not fsync file \"%s\": %m", xlogfname)));
+ }
+
+ pgstat_report_wait_end();
+ if (get_sync_bit(sync_method) != get_sync_bit(new_sync_method))
+ XLogFileClose();
+ }
+ }
+}
+
+
+/*
+ * Issue appropriate kind of fsync (if any) for an XLOG output file.
+ *
+ * 'fd' is a file descriptor for the XLOG file to be fsync'd.
+ * 'segno' is for error reporting purposes.
+ */
+void
+issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
+{
+ char *msg = NULL;
+ instr_time start;
+
+ Assert(tli != 0);
+
+ /*
+ * Quick exit if fsync is disabled or write() has already synced the WAL
+ * file.
+ */
+ if (!enableFsync ||
+ sync_method == SYNC_METHOD_OPEN ||
+ sync_method == SYNC_METHOD_OPEN_DSYNC)
+ return;
+
+ /* Measure I/O timing to sync the WAL file */
+ if (track_wal_io_timing)
+ INSTR_TIME_SET_CURRENT(start);
+
+ pgstat_report_wait_start(WAIT_EVENT_WAL_SYNC);
+ switch (sync_method)
+ {
+ case SYNC_METHOD_FSYNC:
+ if (pg_fsync_no_writethrough(fd) != 0)
+ msg = _("could not fsync file \"%s\": %m");
+ break;
+#ifdef HAVE_FSYNC_WRITETHROUGH
+ case SYNC_METHOD_FSYNC_WRITETHROUGH:
+ if (pg_fsync_writethrough(fd) != 0)
+ msg = _("could not fsync write-through file \"%s\": %m");
+ break;
+#endif
+#ifdef HAVE_FDATASYNC
+ case SYNC_METHOD_FDATASYNC:
+ if (pg_fdatasync(fd) != 0)
+ msg = _("could not fdatasync file \"%s\": %m");
+ break;
+#endif
+ case SYNC_METHOD_OPEN:
+ case SYNC_METHOD_OPEN_DSYNC:
+ /* not reachable */
+ Assert(false);
+ break;
+ default:
+ elog(PANIC, "unrecognized wal_sync_method: %d", sync_method);
+ break;
+ }
+
+ /* PANIC if failed to fsync */
+ if (msg)
+ {
+ char xlogfname[MAXFNAMELEN];
+ int save_errno = errno;
+
+ XLogFileName(xlogfname, tli, segno, wal_segment_size);
+ errno = save_errno;
+ ereport(PANIC,
+ (errcode_for_file_access(),
+ errmsg(msg, xlogfname)));
+ }
+
+ pgstat_report_wait_end();
+
+ /*
+ * Increment the I/O timing and the number of times WAL files were synced.
+ */
+ if (track_wal_io_timing)
+ {
+ instr_time duration;
+
+ INSTR_TIME_SET_CURRENT(duration);
+ INSTR_TIME_SUBTRACT(duration, start);
+ PendingWalStats.wal_sync_time += INSTR_TIME_GET_MICROSEC(duration);
+ }
+
+ PendingWalStats.wal_sync++;
+}
+
+/*
+ * do_pg_backup_start is the workhorse of the user-visible pg_backup_start()
+ * function. It creates the necessary starting checkpoint and constructs the
+ * backup label and tablespace map.
+ *
+ * Input parameters are "backupidstr" (the backup label string) and "fast"
+ * (if true, we do the checkpoint in immediate mode to make it faster).
+ *
+ * The backup label and tablespace map contents are appended to *labelfile and
+ * *tblspcmapfile, and the caller is responsible for including them in the
+ * backup archive as 'backup_label' and 'tablespace_map'.
+ * tblspcmapfile is required mainly for tar format in windows as native windows
+ * utilities are not able to create symlinks while extracting files from tar.
+ * However for consistency and platform-independence, we do it the same way
+ * everywhere.
+ *
+ * If "tablespaces" isn't NULL, it receives a list of tablespaceinfo structs
+ * describing the cluster's tablespaces.
+ *
+ * Returns the minimum WAL location that must be present to restore from this
+ * backup, and the corresponding timeline ID in *starttli_p.
+ *
+ * Every successfully started backup must be stopped by calling
+ * do_pg_backup_stop() or do_pg_abort_backup(). There can be many
+ * backups active at the same time.
+ *
+ * It is the responsibility of the caller of this function to verify the
+ * permissions of the calling user!
+ */
+XLogRecPtr
+do_pg_backup_start(const char *backupidstr, bool fast, TimeLineID *starttli_p,
+ StringInfo labelfile, List **tablespaces,
+ StringInfo tblspcmapfile)
+{
+ bool backup_started_in_recovery = false;
+ XLogRecPtr checkpointloc;
+ XLogRecPtr startpoint;
+ TimeLineID starttli;
+ pg_time_t stamp_time;
+ char strfbuf[128];
+ char xlogfilename[MAXFNAMELEN];
+ XLogSegNo _logSegNo;
+
+ backup_started_in_recovery = RecoveryInProgress();
+
+ /*
+ * During recovery, we don't need to check WAL level. Because, if WAL
+ * level is not sufficient, it's impossible to get here during recovery.
+ */
+ if (!backup_started_in_recovery && !XLogIsNeeded())
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("WAL level not sufficient for making an online backup"),
+ errhint("wal_level must be set to \"replica\" or \"logical\" at server start.")));
+
+ if (strlen(backupidstr) > MAXPGPATH)
+ ereport(ERROR,
+ (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+ errmsg("backup label too long (max %d bytes)",
+ MAXPGPATH)));
+
+ /*
+ * Mark backup active in shared memory. We must do full-page WAL writes
+ * during an on-line backup even if not doing so at other times, because
+ * it's quite possible for the backup dump to obtain a "torn" (partially
+ * written) copy of a database page if it reads the page concurrently with
+ * our write to the same page. This can be fixed as long as the first
+ * write to the page in the WAL sequence is a full-page write. Hence, we
+ * turn on forcePageWrites and then force a CHECKPOINT, to ensure there
+ * are no dirty pages in shared memory that might get dumped while the
+ * backup is in progress without having a corresponding WAL record. (Once
+ * the backup is complete, we need not force full-page writes anymore,
+ * since we expect that any pages not modified during the backup interval
+ * must have been correctly captured by the backup.)
+ *
+ * Note that forcePageWrites has no effect during an online backup from
+ * the standby.
+ *
+ * We must hold all the insertion locks to change the value of
+ * forcePageWrites, to ensure adequate interlocking against
+ * XLogInsertRecord().
+ */
+ WALInsertLockAcquireExclusive();
+ XLogCtl->Insert.runningBackups++;
+ XLogCtl->Insert.forcePageWrites = true;
+ WALInsertLockRelease();
+
+ /* Ensure we release forcePageWrites if fail below */
+ PG_ENSURE_ERROR_CLEANUP(pg_backup_start_callback, (Datum) 0);
+ {
+ bool gotUniqueStartpoint = false;
+ DIR *tblspcdir;
+ struct dirent *de;
+ tablespaceinfo *ti;
+ int datadirpathlen;
+
+ /*
+ * Force an XLOG file switch before the checkpoint, to ensure that the
+ * WAL segment the checkpoint is written to doesn't contain pages with
+ * old timeline IDs. That would otherwise happen if you called
+ * pg_backup_start() right after restoring from a PITR archive: the
+ * first WAL segment containing the startup checkpoint has pages in
+ * the beginning with the old timeline ID. That can cause trouble at
+ * recovery: we won't have a history file covering the old timeline if
+ * pg_wal directory was not included in the base backup and the WAL
+ * archive was cleared too before starting the backup.
+ *
+ * This also ensures that we have emitted a WAL page header that has
+ * XLP_BKP_REMOVABLE off before we emit the checkpoint record.
+ * Therefore, if a WAL archiver (such as pglesslog) is trying to
+ * compress out removable backup blocks, it won't remove any that
+ * occur after this point.
+ *
+ * During recovery, we skip forcing XLOG file switch, which means that
+ * the backup taken during recovery is not available for the special
+ * recovery case described above.
+ */
+ if (!backup_started_in_recovery)
+ RequestXLogSwitch(false);
+
+ do
+ {
+ bool checkpointfpw;
+
+ /*
+ * Force a CHECKPOINT. Aside from being necessary to prevent torn
+ * page problems, this guarantees that two successive backup runs
+ * will have different checkpoint positions and hence different
+ * history file names, even if nothing happened in between.
+ *
+ * During recovery, establish a restartpoint if possible. We use
+ * the last restartpoint as the backup starting checkpoint. This
+ * means that two successive backup runs can have same checkpoint
+ * positions.
+ *
+ * Since the fact that we are executing do_pg_backup_start()
+ * during recovery means that checkpointer is running, we can use
+ * RequestCheckpoint() to establish a restartpoint.
+ *
+ * We use CHECKPOINT_IMMEDIATE only if requested by user (via
+ * passing fast = true). Otherwise this can take awhile.
+ */
+ RequestCheckpoint(CHECKPOINT_FORCE | CHECKPOINT_WAIT |
+ (fast ? CHECKPOINT_IMMEDIATE : 0));
+
+ /*
+ * Now we need to fetch the checkpoint record location, and also
+ * its REDO pointer. The oldest point in WAL that would be needed
+ * to restore starting from the checkpoint is precisely the REDO
+ * pointer.
+ */
+ LWLockAcquire(ControlFileLock, LW_SHARED);
+ checkpointloc = ControlFile->checkPoint;
+ startpoint = ControlFile->checkPointCopy.redo;
+ starttli = ControlFile->checkPointCopy.ThisTimeLineID;
+ checkpointfpw = ControlFile->checkPointCopy.fullPageWrites;
+ LWLockRelease(ControlFileLock);
+
+ if (backup_started_in_recovery)
+ {
+ XLogRecPtr recptr;
+
+ /*
+ * Check to see if all WAL replayed during online backup
+ * (i.e., since last restartpoint used as backup starting
+ * checkpoint) contain full-page writes.
+ */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ recptr = XLogCtl->lastFpwDisableRecPtr;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ if (!checkpointfpw || startpoint <= recptr)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("WAL generated with full_page_writes=off was replayed "
+ "since last restartpoint"),
+ errhint("This means that the backup being taken on the standby "
+ "is corrupt and should not be used. "
+ "Enable full_page_writes and run CHECKPOINT on the primary, "
+ "and then try an online backup again.")));
+
+ /*
+ * During recovery, since we don't use the end-of-backup WAL
+ * record and don't write the backup history file, the
+ * starting WAL location doesn't need to be unique. This means
+ * that two base backups started at the same time might use
+ * the same checkpoint as starting locations.
+ */
+ gotUniqueStartpoint = true;
+ }
+
+ /*
+ * If two base backups are started at the same time (in WAL sender
+ * processes), we need to make sure that they use different
+ * checkpoints as starting locations, because we use the starting
+ * WAL location as a unique identifier for the base backup in the
+ * end-of-backup WAL record and when we write the backup history
+ * file. Perhaps it would be better generate a separate unique ID
+ * for each backup instead of forcing another checkpoint, but
+ * taking a checkpoint right after another is not that expensive
+ * either because only few buffers have been dirtied yet.
+ */
+ WALInsertLockAcquireExclusive();
+ if (XLogCtl->Insert.lastBackupStart < startpoint)
+ {
+ XLogCtl->Insert.lastBackupStart = startpoint;
+ gotUniqueStartpoint = true;
+ }
+ WALInsertLockRelease();
+ } while (!gotUniqueStartpoint);
+
+ XLByteToSeg(startpoint, _logSegNo, wal_segment_size);
+ XLogFileName(xlogfilename, starttli, _logSegNo, wal_segment_size);
+
+ /*
+ * Construct tablespace_map file.
+ */
+ datadirpathlen = strlen(DataDir);
+
+ /* Collect information about all tablespaces */
+ tblspcdir = AllocateDir("pg_tblspc");
+ while ((de = ReadDir(tblspcdir, "pg_tblspc")) != NULL)
+ {
+ char fullpath[MAXPGPATH + 10];
+ char linkpath[MAXPGPATH];
+ char *relpath = NULL;
+ int rllen;
+ StringInfoData escapedpath;
+ char *s;
+
+ /* Skip anything that doesn't look like a tablespace */
+ if (strspn(de->d_name, "0123456789") != strlen(de->d_name))
+ continue;
+
+ snprintf(fullpath, sizeof(fullpath), "pg_tblspc/%s", de->d_name);
+
+ /*
+ * Skip anything that isn't a symlink/junction. For testing only,
+ * we sometimes use allow_in_place_tablespaces to create
+ * directories directly under pg_tblspc, which would fail below.
+ */
+ if (get_dirent_type(fullpath, de, false, ERROR) != PGFILETYPE_LNK)
+ continue;
+
+#if defined(HAVE_READLINK) || defined(WIN32)
+ rllen = readlink(fullpath, linkpath, sizeof(linkpath));
+ if (rllen < 0)
+ {
+ ereport(WARNING,
+ (errmsg("could not read symbolic link \"%s\": %m",
+ fullpath)));
+ continue;
+ }
+ else if (rllen >= sizeof(linkpath))
+ {
+ ereport(WARNING,
+ (errmsg("symbolic link \"%s\" target is too long",
+ fullpath)));
+ continue;
+ }
+ linkpath[rllen] = '\0';
+
+ /*
+ * Build a backslash-escaped version of the link path to include
+ * in the tablespace map file.
+ */
+ initStringInfo(&escapedpath);
+ for (s = linkpath; *s; s++)
+ {
+ if (*s == '\n' || *s == '\r' || *s == '\\')
+ appendStringInfoChar(&escapedpath, '\\');
+ appendStringInfoChar(&escapedpath, *s);
+ }
+
+ /*
+ * Relpath holds the relative path of the tablespace directory
+ * when it's located within PGDATA, or NULL if it's located
+ * elsewhere.
+ */
+ if (rllen > datadirpathlen &&
+ strncmp(linkpath, DataDir, datadirpathlen) == 0 &&
+ IS_DIR_SEP(linkpath[datadirpathlen]))
+ relpath = linkpath + datadirpathlen + 1;
+
+ ti = palloc(sizeof(tablespaceinfo));
+ ti->oid = pstrdup(de->d_name);
+ ti->path = pstrdup(linkpath);
+ ti->rpath = relpath ? pstrdup(relpath) : NULL;
+ ti->size = -1;
+
+ if (tablespaces)
+ *tablespaces = lappend(*tablespaces, ti);
+
+ appendStringInfo(tblspcmapfile, "%s %s\n",
+ ti->oid, escapedpath.data);
+
+ pfree(escapedpath.data);
+#else
+
+ /*
+ * If the platform does not have symbolic links, it should not be
+ * possible to have tablespaces - clearly somebody else created
+ * them. Warn about it and ignore.
+ */
+ ereport(WARNING,
+ (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ errmsg("tablespaces are not supported on this platform")));
+#endif
+ }
+ FreeDir(tblspcdir);
+
+ /*
+ * Construct backup label file.
+ */
+
+ /* Use the log timezone here, not the session timezone */
+ stamp_time = (pg_time_t) time(NULL);
+ pg_strftime(strfbuf, sizeof(strfbuf),
+ "%Y-%m-%d %H:%M:%S %Z",
+ pg_localtime(&stamp_time, log_timezone));
+ appendStringInfo(labelfile, "START WAL LOCATION: %X/%X (file %s)\n",
+ LSN_FORMAT_ARGS(startpoint), xlogfilename);
+ appendStringInfo(labelfile, "CHECKPOINT LOCATION: %X/%X\n",
+ LSN_FORMAT_ARGS(checkpointloc));
+ appendStringInfo(labelfile, "BACKUP METHOD: streamed\n");
+ appendStringInfo(labelfile, "BACKUP FROM: %s\n",
+ backup_started_in_recovery ? "standby" : "primary");
+ appendStringInfo(labelfile, "START TIME: %s\n", strfbuf);
+ appendStringInfo(labelfile, "LABEL: %s\n", backupidstr);
+ appendStringInfo(labelfile, "START TIMELINE: %u\n", starttli);
+ }
+ PG_END_ENSURE_ERROR_CLEANUP(pg_backup_start_callback, (Datum) 0);
+
+ /*
+ * Mark that the start phase has correctly finished for the backup.
+ */
+ sessionBackupState = SESSION_BACKUP_RUNNING;
+
+ /*
+ * We're done. As a convenience, return the starting WAL location.
+ */
+ if (starttli_p)
+ *starttli_p = starttli;
+ return startpoint;
+}
+
+/* Error cleanup callback for pg_backup_start */
+static void
+pg_backup_start_callback(int code, Datum arg)
+{
+ /* Update backup counters and forcePageWrites on failure */
+ WALInsertLockAcquireExclusive();
+
+ Assert(XLogCtl->Insert.runningBackups > 0);
+ XLogCtl->Insert.runningBackups--;
+
+ if (XLogCtl->Insert.runningBackups == 0)
+ {
+ XLogCtl->Insert.forcePageWrites = false;
+ }
+ WALInsertLockRelease();
+}
+
+/*
+ * Utility routine to fetch the session-level status of a backup running.
+ */
+SessionBackupState
+get_backup_status(void)
+{
+ return sessionBackupState;
+}
+
+/*
+ * do_pg_backup_stop
+ *
+ * Utility function called at the end of an online backup. It cleans up the
+ * backup state and can optionally wait for WAL segments to be archived.
+ *
+ * Returns the last WAL location that must be present to restore from this
+ * backup, and the corresponding timeline ID in *stoptli_p.
+ *
+ * It is the responsibility of the caller of this function to verify the
+ * permissions of the calling user!
+ */
+XLogRecPtr
+do_pg_backup_stop(char *labelfile, bool waitforarchive, TimeLineID *stoptli_p)
+{
+ bool backup_started_in_recovery = false;
+ XLogRecPtr startpoint;
+ XLogRecPtr stoppoint;
+ TimeLineID stoptli;
+ pg_time_t stamp_time;
+ char strfbuf[128];
+ char histfilepath[MAXPGPATH];
+ char startxlogfilename[MAXFNAMELEN];
+ char stopxlogfilename[MAXFNAMELEN];
+ char lastxlogfilename[MAXFNAMELEN];
+ char histfilename[MAXFNAMELEN];
+ char backupfrom[20];
+ XLogSegNo _logSegNo;
+ FILE *fp;
+ char ch;
+ int seconds_before_warning;
+ int waits = 0;
+ bool reported_waiting = false;
+ char *remaining;
+ char *ptr;
+ uint32 hi,
+ lo;
+
+ backup_started_in_recovery = RecoveryInProgress();
+
+ /*
+ * During recovery, we don't need to check WAL level. Because, if WAL
+ * level is not sufficient, it's impossible to get here during recovery.
+ */
+ if (!backup_started_in_recovery && !XLogIsNeeded())
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("WAL level not sufficient for making an online backup"),
+ errhint("wal_level must be set to \"replica\" or \"logical\" at server start.")));
+
+ /*
+ * OK to update backup counters, forcePageWrites, and session-level lock.
+ *
+ * Note that CHECK_FOR_INTERRUPTS() must not occur while updating them.
+ * Otherwise they can be updated inconsistently, and which might cause
+ * do_pg_abort_backup() to fail.
+ */
+ WALInsertLockAcquireExclusive();
+
+ /*
+ * It is expected that each do_pg_backup_start() call is matched by
+ * exactly one do_pg_backup_stop() call.
+ */
+ Assert(XLogCtl->Insert.runningBackups > 0);
+ XLogCtl->Insert.runningBackups--;
+
+ if (XLogCtl->Insert.runningBackups == 0)
+ {
+ XLogCtl->Insert.forcePageWrites = false;
+ }
+
+ /*
+ * Clean up session-level lock.
+ *
+ * You might think that WALInsertLockRelease() can be called before
+ * cleaning up session-level lock because session-level lock doesn't need
+ * to be protected with WAL insertion lock. But since
+ * CHECK_FOR_INTERRUPTS() can occur in it, session-level lock must be
+ * cleaned up before it.
+ */
+ sessionBackupState = SESSION_BACKUP_NONE;
+
+ WALInsertLockRelease();
+
+ /*
+ * Read and parse the START WAL LOCATION line (this code is pretty crude,
+ * but we are not expecting any variability in the file format).
+ */
+ if (sscanf(labelfile, "START WAL LOCATION: %X/%X (file %24s)%c",
+ &hi, &lo, startxlogfilename,
+ &ch) != 4 || ch != '\n')
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE)));
+ startpoint = ((uint64) hi) << 32 | lo;
+ remaining = strchr(labelfile, '\n') + 1; /* %n is not portable enough */
+
+ /*
+ * Parse the BACKUP FROM line. If we are taking an online backup from the
+ * standby, we confirm that the standby has not been promoted during the
+ * backup.
+ */
+ ptr = strstr(remaining, "BACKUP FROM:");
+ if (!ptr || sscanf(ptr, "BACKUP FROM: %19s\n", backupfrom) != 1)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("invalid data in file \"%s\"", BACKUP_LABEL_FILE)));
+ if (strcmp(backupfrom, "standby") == 0 && !backup_started_in_recovery)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("the standby was promoted during online backup"),
+ errhint("This means that the backup being taken is corrupt "
+ "and should not be used. "
+ "Try taking another online backup.")));
+
+ /*
+ * During recovery, we don't write an end-of-backup record. We assume that
+ * pg_control was backed up last and its minimum recovery point can be
+ * available as the backup end location. Since we don't have an
+ * end-of-backup record, we use the pg_control value to check whether
+ * we've reached the end of backup when starting recovery from this
+ * backup. We have no way of checking if pg_control wasn't backed up last
+ * however.
+ *
+ * We don't force a switch to new WAL file but it is still possible to
+ * wait for all the required files to be archived if waitforarchive is
+ * true. This is okay if we use the backup to start a standby and fetch
+ * the missing WAL using streaming replication. But in the case of an
+ * archive recovery, a user should set waitforarchive to true and wait for
+ * them to be archived to ensure that all the required files are
+ * available.
+ *
+ * We return the current minimum recovery point as the backup end
+ * location. Note that it can be greater than the exact backup end
+ * location if the minimum recovery point is updated after the backup of
+ * pg_control. This is harmless for current uses.
+ *
+ * XXX currently a backup history file is for informational and debug
+ * purposes only. It's not essential for an online backup. Furthermore,
+ * even if it's created, it will not be archived during recovery because
+ * an archiver is not invoked. So it doesn't seem worthwhile to write a
+ * backup history file during recovery.
+ */
+ if (backup_started_in_recovery)
+ {
+ XLogRecPtr recptr;
+
+ /*
+ * Check to see if all WAL replayed during online backup contain
+ * full-page writes.
+ */
+ SpinLockAcquire(&XLogCtl->info_lck);
+ recptr = XLogCtl->lastFpwDisableRecPtr;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ if (startpoint <= recptr)
+ ereport(ERROR,
+ (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+ errmsg("WAL generated with full_page_writes=off was replayed "
+ "during online backup"),
+ errhint("This means that the backup being taken on the standby "
+ "is corrupt and should not be used. "
+ "Enable full_page_writes and run CHECKPOINT on the primary, "
+ "and then try an online backup again.")));
+
+
+ LWLockAcquire(ControlFileLock, LW_SHARED);
+ stoppoint = ControlFile->minRecoveryPoint;
+ stoptli = ControlFile->minRecoveryPointTLI;
+ LWLockRelease(ControlFileLock);
+ }
+ else
+ {
+ /*
+ * Write the backup-end xlog record
+ */
+ XLogBeginInsert();
+ XLogRegisterData((char *) (&startpoint), sizeof(startpoint));
+ stoppoint = XLogInsert(RM_XLOG_ID, XLOG_BACKUP_END);
+
+ /*
+ * Given that we're not in recovery, InsertTimeLineID is set and can't
+ * change, so we can read it without a lock.
+ */
+ stoptli = XLogCtl->InsertTimeLineID;
+
+ /*
+ * Force a switch to a new xlog segment file, so that the backup is
+ * valid as soon as archiver moves out the current segment file.
+ */
+ RequestXLogSwitch(false);
+
+ XLByteToPrevSeg(stoppoint, _logSegNo, wal_segment_size);
+ XLogFileName(stopxlogfilename, stoptli, _logSegNo, wal_segment_size);
+
+ /* Use the log timezone here, not the session timezone */
+ stamp_time = (pg_time_t) time(NULL);
+ pg_strftime(strfbuf, sizeof(strfbuf),
+ "%Y-%m-%d %H:%M:%S %Z",
+ pg_localtime(&stamp_time, log_timezone));
+
+ /*
+ * Write the backup history file
+ */
+ XLByteToSeg(startpoint, _logSegNo, wal_segment_size);
+ BackupHistoryFilePath(histfilepath, stoptli, _logSegNo,
+ startpoint, wal_segment_size);
+ fp = AllocateFile(histfilepath, "w");
+ if (!fp)
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not create file \"%s\": %m",
+ histfilepath)));
+ fprintf(fp, "START WAL LOCATION: %X/%X (file %s)\n",
+ LSN_FORMAT_ARGS(startpoint), startxlogfilename);
+ fprintf(fp, "STOP WAL LOCATION: %X/%X (file %s)\n",
+ LSN_FORMAT_ARGS(stoppoint), stopxlogfilename);
+
+ /*
+ * Transfer remaining lines including label and start timeline to
+ * history file.
+ */
+ fprintf(fp, "%s", remaining);
+ fprintf(fp, "STOP TIME: %s\n", strfbuf);
+ fprintf(fp, "STOP TIMELINE: %u\n", stoptli);
+ if (fflush(fp) || ferror(fp) || FreeFile(fp))
+ ereport(ERROR,
+ (errcode_for_file_access(),
+ errmsg("could not write file \"%s\": %m",
+ histfilepath)));
+
+ /*
+ * Clean out any no-longer-needed history files. As a side effect,
+ * this will post a .ready file for the newly created history file,
+ * notifying the archiver that history file may be archived
+ * immediately.
+ */
+ CleanupBackupHistory();
+ }
+
+ /*
+ * If archiving is enabled, wait for all the required WAL files to be
+ * archived before returning. If archiving isn't enabled, the required WAL
+ * needs to be transported via streaming replication (hopefully with
+ * wal_keep_size set high enough), or some more exotic mechanism like
+ * polling and copying files from pg_wal with script. We have no knowledge
+ * of those mechanisms, so it's up to the user to ensure that he gets all
+ * the required WAL.
+ *
+ * We wait until both the last WAL file filled during backup and the
+ * history file have been archived, and assume that the alphabetic sorting
+ * property of the WAL files ensures any earlier WAL files are safely
+ * archived as well.
+ *
+ * We wait forever, since archive_command is supposed to work and we
+ * assume the admin wanted his backup to work completely. If you don't
+ * wish to wait, then either waitforarchive should be passed in as false,
+ * or you can set statement_timeout. Also, some notices are issued to
+ * clue in anyone who might be doing this interactively.
+ */
+
+ if (waitforarchive &&
+ ((!backup_started_in_recovery && XLogArchivingActive()) ||
+ (backup_started_in_recovery && XLogArchivingAlways())))
+ {
+ XLByteToPrevSeg(stoppoint, _logSegNo, wal_segment_size);
+ XLogFileName(lastxlogfilename, stoptli, _logSegNo, wal_segment_size);
+
+ XLByteToSeg(startpoint, _logSegNo, wal_segment_size);
+ BackupHistoryFileName(histfilename, stoptli, _logSegNo,
+ startpoint, wal_segment_size);
+
+ seconds_before_warning = 60;
+ waits = 0;
+
+ while (XLogArchiveIsBusy(lastxlogfilename) ||
+ XLogArchiveIsBusy(histfilename))
+ {
+ CHECK_FOR_INTERRUPTS();
+
+ if (!reported_waiting && waits > 5)
+ {
+ ereport(NOTICE,
+ (errmsg("base backup done, waiting for required WAL segments to be archived")));
+ reported_waiting = true;
+ }
+
+ (void) WaitLatch(MyLatch,
+ WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+ 1000L,
+ WAIT_EVENT_BACKUP_WAIT_WAL_ARCHIVE);
+ ResetLatch(MyLatch);
+
+ if (++waits >= seconds_before_warning)
+ {
+ seconds_before_warning *= 2; /* This wraps in >10 years... */
+ ereport(WARNING,
+ (errmsg("still waiting for all required WAL segments to be archived (%d seconds elapsed)",
+ waits),
+ errhint("Check that your archive_command is executing properly. "
+ "You can safely cancel this backup, "
+ "but the database backup will not be usable without all the WAL segments.")));
+ }
+ }
+
+ ereport(NOTICE,
+ (errmsg("all required WAL segments have been archived")));
+ }
+ else if (waitforarchive)
+ ereport(NOTICE,
+ (errmsg("WAL archiving is not enabled; you must ensure that all required WAL segments are copied through other means to complete the backup")));
+
+ /*
+ * We're done. As a convenience, return the ending WAL location.
+ */
+ if (stoptli_p)
+ *stoptli_p = stoptli;
+ return stoppoint;
+}
+
+
+/*
+ * do_pg_abort_backup: abort a running backup
+ *
+ * This does just the most basic steps of do_pg_backup_stop(), by taking the
+ * system out of backup mode, thus making it a lot more safe to call from
+ * an error handler.
+ *
+ * The caller can pass 'arg' as 'true' or 'false' to control whether a warning
+ * is emitted.
+ *
+ * NB: This gets used as a before_shmem_exit handler, hence the odd-looking
+ * signature.
+ */
+void
+do_pg_abort_backup(int code, Datum arg)
+{
+ bool emit_warning = DatumGetBool(arg);
+
+ /*
+ * Quick exit if session does not have a running backup.
+ */
+ if (sessionBackupState != SESSION_BACKUP_RUNNING)
+ return;
+
+ WALInsertLockAcquireExclusive();
+ Assert(XLogCtl->Insert.runningBackups > 0);
+ XLogCtl->Insert.runningBackups--;
+
+ if (XLogCtl->Insert.runningBackups == 0)
+ {
+ XLogCtl->Insert.forcePageWrites = false;
+ }
+
+ sessionBackupState = SESSION_BACKUP_NONE;
+ WALInsertLockRelease();
+
+ if (emit_warning)
+ ereport(WARNING,
+ (errmsg("aborting backup due to backend exiting before pg_backup_stop was called")));
+}
+
+/*
+ * Register a handler that will warn about unterminated backups at end of
+ * session, unless this has already been done.
+ */
+void
+register_persistent_abort_backup_handler(void)
+{
+ static bool already_done = false;
+
+ if (already_done)
+ return;
+ before_shmem_exit(do_pg_abort_backup, DatumGetBool(true));
+ already_done = true;
+}
+
+/*
+ * Get latest WAL insert pointer
+ */
+XLogRecPtr
+GetXLogInsertRecPtr(void)
+{
+ XLogCtlInsert *Insert = &XLogCtl->Insert;
+ uint64 current_bytepos;
+
+ SpinLockAcquire(&Insert->insertpos_lck);
+ current_bytepos = Insert->CurrBytePos;
+ SpinLockRelease(&Insert->insertpos_lck);
+
+ return XLogBytePosToRecPtr(current_bytepos);
+}
+
+/*
+ * Get latest WAL write pointer
+ */
+XLogRecPtr
+GetXLogWriteRecPtr(void)
+{
+ SpinLockAcquire(&XLogCtl->info_lck);
+ LogwrtResult = XLogCtl->LogwrtResult;
+ SpinLockRelease(&XLogCtl->info_lck);
+
+ return LogwrtResult.Write;
+}
+
+/*
+ * Returns the redo pointer of the last checkpoint or restartpoint. This is
+ * the oldest point in WAL that we still need, if we have to restart recovery.
+ */
+void
+GetOldestRestartPoint(XLogRecPtr *oldrecptr, TimeLineID *oldtli)
+{
+ LWLockAcquire(ControlFileLock, LW_SHARED);
+ *oldrecptr = ControlFile->checkPointCopy.redo;
+ *oldtli = ControlFile->checkPointCopy.ThisTimeLineID;
+ LWLockRelease(ControlFileLock);
+}
+
+/* Thin wrapper around ShutdownWalRcv(). */
+void
+XLogShutdownWalRcv(void)
+{
+ ShutdownWalRcv();
+
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ XLogCtl->InstallXLogFileSegmentActive = false;
+ LWLockRelease(ControlFileLock);
+}
+
+/* Enable WAL file recycling and preallocation. */
+void
+SetInstallXLogFileSegmentActive(void)
+{
+ LWLockAcquire(ControlFileLock, LW_EXCLUSIVE);
+ XLogCtl->InstallXLogFileSegmentActive = true;
+ LWLockRelease(ControlFileLock);
+}
+
+bool
+IsInstallXLogFileSegmentActive(void)
+{
+ bool result;
+
+ LWLockAcquire(ControlFileLock, LW_SHARED);
+ result = XLogCtl->InstallXLogFileSegmentActive;
+ LWLockRelease(ControlFileLock);
+
+ return result;
+}
+
+/*
+ * Update the WalWriterSleeping flag.
+ */
+void
+SetWalWriterSleeping(bool sleeping)
+{
+ SpinLockAcquire(&XLogCtl->info_lck);
+ XLogCtl->WalWriterSleeping = sleeping;
+ SpinLockRelease(&XLogCtl->info_lck);
+}