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Diffstat (limited to 'src/backend/replication/logical/logical.c')
| -rw-r--r-- | src/backend/replication/logical/logical.c | 1093 |
1 files changed, 1093 insertions, 0 deletions
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c new file mode 100644 index 0000000..61902be --- /dev/null +++ b/src/backend/replication/logical/logical.c @@ -0,0 +1,1093 @@ +/*------------------------------------------------------------------------- + * logical.c + * PostgreSQL logical decoding coordination + * + * Copyright (c) 2012-2020, PostgreSQL Global Development Group + * + * IDENTIFICATION + * src/backend/replication/logical/logical.c + * + * NOTES + * This file coordinates interaction between the various modules that + * together provide logical decoding, primarily by providing so + * called LogicalDecodingContexts. The goal is to encapsulate most of the + * internal complexity for consumers of logical decoding, so they can + * create and consume a changestream with a low amount of code. Builtin + * consumers are the walsender and SQL SRF interface, but it's possible to + * add further ones without changing core code, e.g. to consume changes in + * a bgworker. + * + * The idea is that a consumer provides three callbacks, one to read WAL, + * one to prepare a data write, and a final one for actually writing since + * their implementation depends on the type of consumer. Check + * logicalfuncs.c for an example implementation of a fairly simple consumer + * and an implementation of a WAL reading callback that's suitable for + * simple consumers. + *------------------------------------------------------------------------- + */ + +#include "postgres.h" + +#include "access/xact.h" +#include "access/xlog_internal.h" +#include "fmgr.h" +#include "miscadmin.h" +#include "replication/decode.h" +#include "replication/logical.h" +#include "replication/origin.h" +#include "replication/reorderbuffer.h" +#include "replication/snapbuild.h" +#include "storage/proc.h" +#include "storage/procarray.h" +#include "utils/memutils.h" + +/* data for errcontext callback */ +typedef struct LogicalErrorCallbackState +{ + LogicalDecodingContext *ctx; + const char *callback_name; + XLogRecPtr report_location; +} LogicalErrorCallbackState; + +/* wrappers around output plugin callbacks */ +static void output_plugin_error_callback(void *arg); +static void startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, + bool is_init); +static void shutdown_cb_wrapper(LogicalDecodingContext *ctx); +static void begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn); +static void commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + XLogRecPtr commit_lsn); +static void change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + Relation relation, ReorderBufferChange *change); +static void truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + int nrelations, Relation relations[], ReorderBufferChange *change); +static void message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + XLogRecPtr message_lsn, bool transactional, + const char *prefix, Size message_size, const char *message); + +static void LoadOutputPlugin(OutputPluginCallbacks *callbacks, char *plugin); + +/* + * Make sure the current settings & environment are capable of doing logical + * decoding. + */ +void +CheckLogicalDecodingRequirements(void) +{ + CheckSlotRequirements(); + + /* + * NB: Adding a new requirement likely means that RestoreSlotFromDisk() + * needs the same check. + */ + + if (wal_level < WAL_LEVEL_LOGICAL) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("logical decoding requires wal_level >= logical"))); + + if (MyDatabaseId == InvalidOid) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("logical decoding requires a database connection"))); + + /* ---- + * TODO: We got to change that someday soon... + * + * There's basically three things missing to allow this: + * 1) We need to be able to correctly and quickly identify the timeline a + * LSN belongs to + * 2) We need to force hot_standby_feedback to be enabled at all times so + * the primary cannot remove rows we need. + * 3) support dropping replication slots referring to a database, in + * dbase_redo. There can't be any active ones due to HS recovery + * conflicts, so that should be relatively easy. + * ---- + */ + if (RecoveryInProgress()) + ereport(ERROR, + (errcode(ERRCODE_FEATURE_NOT_SUPPORTED), + errmsg("logical decoding cannot be used while in recovery"))); +} + +/* + * Helper function for CreateInitDecodingContext() and + * CreateDecodingContext() performing common tasks. + */ +static LogicalDecodingContext * +StartupDecodingContext(List *output_plugin_options, + XLogRecPtr start_lsn, + TransactionId xmin_horizon, + bool need_full_snapshot, + bool fast_forward, + XLogReaderRoutine *xl_routine, + LogicalOutputPluginWriterPrepareWrite prepare_write, + LogicalOutputPluginWriterWrite do_write, + LogicalOutputPluginWriterUpdateProgress update_progress) +{ + ReplicationSlot *slot; + MemoryContext context, + old_context; + LogicalDecodingContext *ctx; + + /* shorter lines... */ + slot = MyReplicationSlot; + + context = AllocSetContextCreate(CurrentMemoryContext, + "Logical decoding context", + ALLOCSET_DEFAULT_SIZES); + old_context = MemoryContextSwitchTo(context); + ctx = palloc0(sizeof(LogicalDecodingContext)); + + ctx->context = context; + + /* + * (re-)load output plugins, so we detect a bad (removed) output plugin + * now. + */ + if (!fast_forward) + LoadOutputPlugin(&ctx->callbacks, NameStr(slot->data.plugin)); + + /* + * Now that the slot's xmin has been set, we can announce ourselves as a + * logical decoding backend which doesn't need to be checked individually + * when computing the xmin horizon because the xmin is enforced via + * replication slots. + * + * We can only do so if we're outside of a transaction (i.e. the case when + * streaming changes via walsender), otherwise an already setup + * snapshot/xid would end up being ignored. That's not a particularly + * bothersome restriction since the SQL interface can't be used for + * streaming anyway. + */ + if (!IsTransactionOrTransactionBlock()) + { + LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); + MyPgXact->vacuumFlags |= PROC_IN_LOGICAL_DECODING; + LWLockRelease(ProcArrayLock); + } + + ctx->slot = slot; + + ctx->reader = XLogReaderAllocate(wal_segment_size, NULL, xl_routine, ctx); + if (!ctx->reader) + ereport(ERROR, + (errcode(ERRCODE_OUT_OF_MEMORY), + errmsg("out of memory"))); + + ctx->reorder = ReorderBufferAllocate(); + ctx->snapshot_builder = + AllocateSnapshotBuilder(ctx->reorder, xmin_horizon, start_lsn, + need_full_snapshot); + + ctx->reorder->private_data = ctx; + + /* wrap output plugin callbacks, so we can add error context information */ + ctx->reorder->begin = begin_cb_wrapper; + ctx->reorder->apply_change = change_cb_wrapper; + ctx->reorder->apply_truncate = truncate_cb_wrapper; + ctx->reorder->commit = commit_cb_wrapper; + ctx->reorder->message = message_cb_wrapper; + + ctx->out = makeStringInfo(); + ctx->prepare_write = prepare_write; + ctx->write = do_write; + ctx->update_progress = update_progress; + + ctx->output_plugin_options = output_plugin_options; + + ctx->fast_forward = fast_forward; + + MemoryContextSwitchTo(old_context); + + return ctx; +} + +/* + * Create a new decoding context, for a new logical slot. + * + * plugin -- contains the name of the output plugin + * output_plugin_options -- contains options passed to the output plugin + * need_full_snapshot -- if true, must obtain a snapshot able to read all + * tables; if false, one that can read only catalogs is acceptable. + * restart_lsn -- if given as invalid, it's this routine's responsibility to + * mark WAL as reserved by setting a convenient restart_lsn for the slot. + * Otherwise, we set for decoding to start from the given LSN without + * marking WAL reserved beforehand. In that scenario, it's up to the + * caller to guarantee that WAL remains available. + * xl_routine -- XLogReaderRoutine for underlying XLogReader + * prepare_write, do_write, update_progress -- + * callbacks that perform the use-case dependent, actual, work. + * + * Needs to be called while in a memory context that's at least as long lived + * as the decoding context because further memory contexts will be created + * inside it. + * + * Returns an initialized decoding context after calling the output plugin's + * startup function. + */ +LogicalDecodingContext * +CreateInitDecodingContext(char *plugin, + List *output_plugin_options, + bool need_full_snapshot, + XLogRecPtr restart_lsn, + XLogReaderRoutine *xl_routine, + LogicalOutputPluginWriterPrepareWrite prepare_write, + LogicalOutputPluginWriterWrite do_write, + LogicalOutputPluginWriterUpdateProgress update_progress) +{ + TransactionId xmin_horizon = InvalidTransactionId; + ReplicationSlot *slot; + LogicalDecodingContext *ctx; + MemoryContext old_context; + + /* shorter lines... */ + slot = MyReplicationSlot; + + /* first some sanity checks that are unlikely to be violated */ + if (slot == NULL) + elog(ERROR, "cannot perform logical decoding without an acquired slot"); + + if (plugin == NULL) + elog(ERROR, "cannot initialize logical decoding without a specified plugin"); + + /* Make sure the passed slot is suitable. These are user facing errors. */ + if (SlotIsPhysical(slot)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot use physical replication slot for logical decoding"))); + + if (slot->data.database != MyDatabaseId) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("replication slot \"%s\" was not created in this database", + NameStr(slot->data.name)))); + + if (IsTransactionState() && + GetTopTransactionIdIfAny() != InvalidTransactionId) + ereport(ERROR, + (errcode(ERRCODE_ACTIVE_SQL_TRANSACTION), + errmsg("cannot create logical replication slot in transaction that has performed writes"))); + + /* register output plugin name with slot */ + SpinLockAcquire(&slot->mutex); + StrNCpy(NameStr(slot->data.plugin), plugin, NAMEDATALEN); + SpinLockRelease(&slot->mutex); + + if (XLogRecPtrIsInvalid(restart_lsn)) + ReplicationSlotReserveWal(); + else + { + SpinLockAcquire(&slot->mutex); + slot->data.restart_lsn = restart_lsn; + SpinLockRelease(&slot->mutex); + } + + /* ---- + * This is a bit tricky: We need to determine a safe xmin horizon to start + * decoding from, to avoid starting from a running xacts record referring + * to xids whose rows have been vacuumed or pruned + * already. GetOldestSafeDecodingTransactionId() returns such a value, but + * without further interlock its return value might immediately be out of + * date. + * + * So we have to acquire the ProcArrayLock to prevent computation of new + * xmin horizons by other backends, get the safe decoding xid, and inform + * the slot machinery about the new limit. Once that's done the + * ProcArrayLock can be released as the slot machinery now is + * protecting against vacuum. + * + * Note that, temporarily, the data, not just the catalog, xmin has to be + * reserved if a data snapshot is to be exported. Otherwise the initial + * data snapshot created here is not guaranteed to be valid. After that + * the data xmin doesn't need to be managed anymore and the global xmin + * should be recomputed. As we are fine with losing the pegged data xmin + * after crash - no chance a snapshot would get exported anymore - we can + * get away with just setting the slot's + * effective_xmin. ReplicationSlotRelease will reset it again. + * + * ---- + */ + LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE); + + xmin_horizon = GetOldestSafeDecodingTransactionId(!need_full_snapshot); + + SpinLockAcquire(&slot->mutex); + slot->effective_catalog_xmin = xmin_horizon; + slot->data.catalog_xmin = xmin_horizon; + if (need_full_snapshot) + slot->effective_xmin = xmin_horizon; + SpinLockRelease(&slot->mutex); + + ReplicationSlotsComputeRequiredXmin(true); + + LWLockRelease(ProcArrayLock); + + ReplicationSlotMarkDirty(); + ReplicationSlotSave(); + + ctx = StartupDecodingContext(NIL, restart_lsn, xmin_horizon, + need_full_snapshot, false, + xl_routine, prepare_write, do_write, + update_progress); + + /* call output plugin initialization callback */ + old_context = MemoryContextSwitchTo(ctx->context); + if (ctx->callbacks.startup_cb != NULL) + startup_cb_wrapper(ctx, &ctx->options, true); + MemoryContextSwitchTo(old_context); + + ctx->reorder->output_rewrites = ctx->options.receive_rewrites; + + return ctx; +} + +/* + * Create a new decoding context, for a logical slot that has previously been + * used already. + * + * start_lsn + * The LSN at which to start decoding. If InvalidXLogRecPtr, restart + * from the slot's confirmed_flush; otherwise, start from the specified + * location (but move it forwards to confirmed_flush if it's older than + * that, see below). + * + * output_plugin_options + * options passed to the output plugin. + * + * fast_forward + * bypass the generation of logical changes. + * + * xl_routine + * XLogReaderRoutine used by underlying xlogreader + * + * prepare_write, do_write, update_progress + * callbacks that have to be filled to perform the use-case dependent, + * actual work. + * + * Needs to be called while in a memory context that's at least as long lived + * as the decoding context because further memory contexts will be created + * inside it. + * + * Returns an initialized decoding context after calling the output plugin's + * startup function. + */ +LogicalDecodingContext * +CreateDecodingContext(XLogRecPtr start_lsn, + List *output_plugin_options, + bool fast_forward, + XLogReaderRoutine *xl_routine, + LogicalOutputPluginWriterPrepareWrite prepare_write, + LogicalOutputPluginWriterWrite do_write, + LogicalOutputPluginWriterUpdateProgress update_progress) +{ + LogicalDecodingContext *ctx; + ReplicationSlot *slot; + MemoryContext old_context; + + /* shorter lines... */ + slot = MyReplicationSlot; + + /* first some sanity checks that are unlikely to be violated */ + if (slot == NULL) + elog(ERROR, "cannot perform logical decoding without an acquired slot"); + + /* make sure the passed slot is suitable, these are user facing errors */ + if (SlotIsPhysical(slot)) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot use physical replication slot for logical decoding"))); + + if (slot->data.database != MyDatabaseId) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("replication slot \"%s\" was not created in this database", + NameStr(slot->data.name)))); + + if (start_lsn == InvalidXLogRecPtr) + { + /* continue from last position */ + start_lsn = slot->data.confirmed_flush; + } + else if (start_lsn < slot->data.confirmed_flush) + { + /* + * It might seem like we should error out in this case, but it's + * pretty common for a client to acknowledge a LSN it doesn't have to + * do anything for, and thus didn't store persistently, because the + * xlog records didn't result in anything relevant for logical + * decoding. Clients have to be able to do that to support synchronous + * replication. + */ + elog(DEBUG1, "cannot stream from %X/%X, minimum is %X/%X, forwarding", + (uint32) (start_lsn >> 32), (uint32) start_lsn, + (uint32) (slot->data.confirmed_flush >> 32), + (uint32) slot->data.confirmed_flush); + + start_lsn = slot->data.confirmed_flush; + } + + ctx = StartupDecodingContext(output_plugin_options, + start_lsn, InvalidTransactionId, false, + fast_forward, xl_routine, prepare_write, + do_write, update_progress); + + /* call output plugin initialization callback */ + old_context = MemoryContextSwitchTo(ctx->context); + if (ctx->callbacks.startup_cb != NULL) + startup_cb_wrapper(ctx, &ctx->options, false); + MemoryContextSwitchTo(old_context); + + ctx->reorder->output_rewrites = ctx->options.receive_rewrites; + + ereport(LOG, + (errmsg("starting logical decoding for slot \"%s\"", + NameStr(slot->data.name)), + errdetail("Streaming transactions committing after %X/%X, reading WAL from %X/%X.", + (uint32) (slot->data.confirmed_flush >> 32), + (uint32) slot->data.confirmed_flush, + (uint32) (slot->data.restart_lsn >> 32), + (uint32) slot->data.restart_lsn))); + + return ctx; +} + +/* + * Returns true if a consistent initial decoding snapshot has been built. + */ +bool +DecodingContextReady(LogicalDecodingContext *ctx) +{ + return SnapBuildCurrentState(ctx->snapshot_builder) == SNAPBUILD_CONSISTENT; +} + +/* + * Read from the decoding slot, until it is ready to start extracting changes. + */ +void +DecodingContextFindStartpoint(LogicalDecodingContext *ctx) +{ + ReplicationSlot *slot = ctx->slot; + + /* Initialize from where to start reading WAL. */ + XLogBeginRead(ctx->reader, slot->data.restart_lsn); + + elog(DEBUG1, "searching for logical decoding starting point, starting at %X/%X", + (uint32) (slot->data.restart_lsn >> 32), + (uint32) slot->data.restart_lsn); + + /* Wait for a consistent starting point */ + for (;;) + { + XLogRecord *record; + char *err = NULL; + + /* the read_page callback waits for new WAL */ + record = XLogReadRecord(ctx->reader, &err); + if (err) + elog(ERROR, "%s", err); + if (!record) + elog(ERROR, "no record found"); /* shouldn't happen */ + + LogicalDecodingProcessRecord(ctx, ctx->reader); + + /* only continue till we found a consistent spot */ + if (DecodingContextReady(ctx)) + break; + + CHECK_FOR_INTERRUPTS(); + } + + SpinLockAcquire(&slot->mutex); + slot->data.confirmed_flush = ctx->reader->EndRecPtr; + SpinLockRelease(&slot->mutex); +} + +/* + * Free a previously allocated decoding context, invoking the shutdown + * callback if necessary. + */ +void +FreeDecodingContext(LogicalDecodingContext *ctx) +{ + if (ctx->callbacks.shutdown_cb != NULL) + shutdown_cb_wrapper(ctx); + + ReorderBufferFree(ctx->reorder); + FreeSnapshotBuilder(ctx->snapshot_builder); + XLogReaderFree(ctx->reader); + MemoryContextDelete(ctx->context); +} + +/* + * Prepare a write using the context's output routine. + */ +void +OutputPluginPrepareWrite(struct LogicalDecodingContext *ctx, bool last_write) +{ + if (!ctx->accept_writes) + elog(ERROR, "writes are only accepted in commit, begin and change callbacks"); + + ctx->prepare_write(ctx, ctx->write_location, ctx->write_xid, last_write); + ctx->prepared_write = true; +} + +/* + * Perform a write using the context's output routine. + */ +void +OutputPluginWrite(struct LogicalDecodingContext *ctx, bool last_write) +{ + if (!ctx->prepared_write) + elog(ERROR, "OutputPluginPrepareWrite needs to be called before OutputPluginWrite"); + + ctx->write(ctx, ctx->write_location, ctx->write_xid, last_write); + ctx->prepared_write = false; +} + +/* + * Update progress tracking (if supported). + */ +void +OutputPluginUpdateProgress(struct LogicalDecodingContext *ctx) +{ + if (!ctx->update_progress) + return; + + ctx->update_progress(ctx, ctx->write_location, ctx->write_xid); +} + +/* + * Load the output plugin, lookup its output plugin init function, and check + * that it provides the required callbacks. + */ +static void +LoadOutputPlugin(OutputPluginCallbacks *callbacks, char *plugin) +{ + LogicalOutputPluginInit plugin_init; + + plugin_init = (LogicalOutputPluginInit) + load_external_function(plugin, "_PG_output_plugin_init", false, NULL); + + if (plugin_init == NULL) + elog(ERROR, "output plugins have to declare the _PG_output_plugin_init symbol"); + + /* ask the output plugin to fill the callback struct */ + plugin_init(callbacks); + + if (callbacks->begin_cb == NULL) + elog(ERROR, "output plugins have to register a begin callback"); + if (callbacks->change_cb == NULL) + elog(ERROR, "output plugins have to register a change callback"); + if (callbacks->commit_cb == NULL) + elog(ERROR, "output plugins have to register a commit callback"); +} + +static void +output_plugin_error_callback(void *arg) +{ + LogicalErrorCallbackState *state = (LogicalErrorCallbackState *) arg; + + /* not all callbacks have an associated LSN */ + if (state->report_location != InvalidXLogRecPtr) + errcontext("slot \"%s\", output plugin \"%s\", in the %s callback, associated LSN %X/%X", + NameStr(state->ctx->slot->data.name), + NameStr(state->ctx->slot->data.plugin), + state->callback_name, + (uint32) (state->report_location >> 32), + (uint32) state->report_location); + else + errcontext("slot \"%s\", output plugin \"%s\", in the %s callback", + NameStr(state->ctx->slot->data.name), + NameStr(state->ctx->slot->data.plugin), + state->callback_name); +} + +static void +startup_cb_wrapper(LogicalDecodingContext *ctx, OutputPluginOptions *opt, bool is_init) +{ + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + Assert(!ctx->fast_forward); + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "startup"; + state.report_location = InvalidXLogRecPtr; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = false; + + /* do the actual work: call callback */ + ctx->callbacks.startup_cb(ctx, opt, is_init); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +static void +shutdown_cb_wrapper(LogicalDecodingContext *ctx) +{ + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + Assert(!ctx->fast_forward); + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "shutdown"; + state.report_location = InvalidXLogRecPtr; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = false; + + /* do the actual work: call callback */ + ctx->callbacks.shutdown_cb(ctx); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + + +/* + * Callbacks for ReorderBuffer which add in some more information and then call + * output_plugin.h plugins. + */ +static void +begin_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + Assert(!ctx->fast_forward); + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "begin"; + state.report_location = txn->first_lsn; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn->xid; + ctx->write_location = txn->first_lsn; + + /* do the actual work: call callback */ + ctx->callbacks.begin_cb(ctx, txn); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +static void +commit_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + XLogRecPtr commit_lsn) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + Assert(!ctx->fast_forward); + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "commit"; + state.report_location = txn->final_lsn; /* beginning of commit record */ + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn->xid; + ctx->write_location = txn->end_lsn; /* points to the end of the record */ + + /* do the actual work: call callback */ + ctx->callbacks.commit_cb(ctx, txn, commit_lsn); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +static void +change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + Relation relation, ReorderBufferChange *change) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + Assert(!ctx->fast_forward); + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "change"; + state.report_location = change->lsn; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn->xid; + + /* + * report this change's lsn so replies from clients can give an up2date + * answer. This won't ever be enough (and shouldn't be!) to confirm + * receipt of this transaction, but it might allow another transaction's + * commit to be confirmed with one message. + */ + ctx->write_location = change->lsn; + + ctx->callbacks.change_cb(ctx, txn, relation, change); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +static void +truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + int nrelations, Relation relations[], ReorderBufferChange *change) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + Assert(!ctx->fast_forward); + + if (!ctx->callbacks.truncate_cb) + return; + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "truncate"; + state.report_location = change->lsn; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn->xid; + + /* + * report this change's lsn so replies from clients can give an up2date + * answer. This won't ever be enough (and shouldn't be!) to confirm + * receipt of this transaction, but it might allow another transaction's + * commit to be confirmed with one message. + */ + ctx->write_location = change->lsn; + + ctx->callbacks.truncate_cb(ctx, txn, nrelations, relations, change); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +bool +filter_by_origin_cb_wrapper(LogicalDecodingContext *ctx, RepOriginId origin_id) +{ + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + bool ret; + + Assert(!ctx->fast_forward); + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "filter_by_origin"; + state.report_location = InvalidXLogRecPtr; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = false; + + /* do the actual work: call callback */ + ret = ctx->callbacks.filter_by_origin_cb(ctx, origin_id); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; + + return ret; +} + +static void +message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn, + XLogRecPtr message_lsn, bool transactional, + const char *prefix, Size message_size, const char *message) +{ + LogicalDecodingContext *ctx = cache->private_data; + LogicalErrorCallbackState state; + ErrorContextCallback errcallback; + + Assert(!ctx->fast_forward); + + if (ctx->callbacks.message_cb == NULL) + return; + + /* Push callback + info on the error context stack */ + state.ctx = ctx; + state.callback_name = "message"; + state.report_location = message_lsn; + errcallback.callback = output_plugin_error_callback; + errcallback.arg = (void *) &state; + errcallback.previous = error_context_stack; + error_context_stack = &errcallback; + + /* set output state */ + ctx->accept_writes = true; + ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId; + ctx->write_location = message_lsn; + + /* do the actual work: call callback */ + ctx->callbacks.message_cb(ctx, txn, message_lsn, transactional, prefix, + message_size, message); + + /* Pop the error context stack */ + error_context_stack = errcallback.previous; +} + +/* + * Set the required catalog xmin horizon for historic snapshots in the current + * replication slot. + * + * Note that in the most cases, we won't be able to immediately use the xmin + * to increase the xmin horizon: we need to wait till the client has confirmed + * receiving current_lsn with LogicalConfirmReceivedLocation(). + */ +void +LogicalIncreaseXminForSlot(XLogRecPtr current_lsn, TransactionId xmin) +{ + bool updated_xmin = false; + ReplicationSlot *slot; + + slot = MyReplicationSlot; + + Assert(slot != NULL); + + SpinLockAcquire(&slot->mutex); + + /* + * don't overwrite if we already have a newer xmin. This can happen if we + * restart decoding in a slot. + */ + if (TransactionIdPrecedesOrEquals(xmin, slot->data.catalog_xmin)) + { + } + + /* + * If the client has already confirmed up to this lsn, we directly can + * mark this as accepted. This can happen if we restart decoding in a + * slot. + */ + else if (current_lsn <= slot->data.confirmed_flush) + { + slot->candidate_catalog_xmin = xmin; + slot->candidate_xmin_lsn = current_lsn; + + /* our candidate can directly be used */ + updated_xmin = true; + } + + /* + * Only increase if the previous values have been applied, otherwise we + * might never end up updating if the receiver acks too slowly. + */ + else if (slot->candidate_xmin_lsn == InvalidXLogRecPtr) + { + slot->candidate_catalog_xmin = xmin; + slot->candidate_xmin_lsn = current_lsn; + } + SpinLockRelease(&slot->mutex); + + /* candidate already valid with the current flush position, apply */ + if (updated_xmin) + LogicalConfirmReceivedLocation(slot->data.confirmed_flush); +} + +/* + * Mark the minimal LSN (restart_lsn) we need to read to replay all + * transactions that have not yet committed at current_lsn. + * + * Just like LogicalIncreaseXminForSlot this only takes effect when the + * client has confirmed to have received current_lsn. + */ +void +LogicalIncreaseRestartDecodingForSlot(XLogRecPtr current_lsn, XLogRecPtr restart_lsn) +{ + bool updated_lsn = false; + ReplicationSlot *slot; + + slot = MyReplicationSlot; + + Assert(slot != NULL); + Assert(restart_lsn != InvalidXLogRecPtr); + Assert(current_lsn != InvalidXLogRecPtr); + + SpinLockAcquire(&slot->mutex); + + /* don't overwrite if have a newer restart lsn */ + if (restart_lsn <= slot->data.restart_lsn) + { + } + + /* + * We might have already flushed far enough to directly accept this lsn, + * in this case there is no need to check for existing candidate LSNs + */ + else if (current_lsn <= slot->data.confirmed_flush) + { + slot->candidate_restart_valid = current_lsn; + slot->candidate_restart_lsn = restart_lsn; + + /* our candidate can directly be used */ + updated_lsn = true; + } + + /* + * Only increase if the previous values have been applied, otherwise we + * might never end up updating if the receiver acks too slowly. A missed + * value here will just cause some extra effort after reconnecting. + */ + if (slot->candidate_restart_valid == InvalidXLogRecPtr) + { + slot->candidate_restart_valid = current_lsn; + slot->candidate_restart_lsn = restart_lsn; + SpinLockRelease(&slot->mutex); + + elog(DEBUG1, "got new restart lsn %X/%X at %X/%X", + (uint32) (restart_lsn >> 32), (uint32) restart_lsn, + (uint32) (current_lsn >> 32), (uint32) current_lsn); + } + else + { + XLogRecPtr candidate_restart_lsn; + XLogRecPtr candidate_restart_valid; + XLogRecPtr confirmed_flush; + + candidate_restart_lsn = slot->candidate_restart_lsn; + candidate_restart_valid = slot->candidate_restart_valid; + confirmed_flush = slot->data.confirmed_flush; + SpinLockRelease(&slot->mutex); + + elog(DEBUG1, "failed to increase restart lsn: proposed %X/%X, after %X/%X, current candidate %X/%X, current after %X/%X, flushed up to %X/%X", + (uint32) (restart_lsn >> 32), (uint32) restart_lsn, + (uint32) (current_lsn >> 32), (uint32) current_lsn, + (uint32) (candidate_restart_lsn >> 32), + (uint32) candidate_restart_lsn, + (uint32) (candidate_restart_valid >> 32), + (uint32) candidate_restart_valid, + (uint32) (confirmed_flush >> 32), + (uint32) confirmed_flush); + } + + /* candidates are already valid with the current flush position, apply */ + if (updated_lsn) + LogicalConfirmReceivedLocation(slot->data.confirmed_flush); +} + +/* + * Handle a consumer's confirmation having received all changes up to lsn. + */ +void +LogicalConfirmReceivedLocation(XLogRecPtr lsn) +{ + Assert(lsn != InvalidXLogRecPtr); + + /* Do an unlocked check for candidate_lsn first. */ + if (MyReplicationSlot->candidate_xmin_lsn != InvalidXLogRecPtr || + MyReplicationSlot->candidate_restart_valid != InvalidXLogRecPtr) + { + bool updated_xmin = false; + bool updated_restart = false; + + SpinLockAcquire(&MyReplicationSlot->mutex); + + MyReplicationSlot->data.confirmed_flush = lsn; + + /* if we're past the location required for bumping xmin, do so */ + if (MyReplicationSlot->candidate_xmin_lsn != InvalidXLogRecPtr && + MyReplicationSlot->candidate_xmin_lsn <= lsn) + { + /* + * We have to write the changed xmin to disk *before* we change + * the in-memory value, otherwise after a crash we wouldn't know + * that some catalog tuples might have been removed already. + * + * Ensure that by first writing to ->xmin and only update + * ->effective_xmin once the new state is synced to disk. After a + * crash ->effective_xmin is set to ->xmin. + */ + if (TransactionIdIsValid(MyReplicationSlot->candidate_catalog_xmin) && + MyReplicationSlot->data.catalog_xmin != MyReplicationSlot->candidate_catalog_xmin) + { + MyReplicationSlot->data.catalog_xmin = MyReplicationSlot->candidate_catalog_xmin; + MyReplicationSlot->candidate_catalog_xmin = InvalidTransactionId; + MyReplicationSlot->candidate_xmin_lsn = InvalidXLogRecPtr; + updated_xmin = true; + } + } + + if (MyReplicationSlot->candidate_restart_valid != InvalidXLogRecPtr && + MyReplicationSlot->candidate_restart_valid <= lsn) + { + Assert(MyReplicationSlot->candidate_restart_lsn != InvalidXLogRecPtr); + + MyReplicationSlot->data.restart_lsn = MyReplicationSlot->candidate_restart_lsn; + MyReplicationSlot->candidate_restart_lsn = InvalidXLogRecPtr; + MyReplicationSlot->candidate_restart_valid = InvalidXLogRecPtr; + updated_restart = true; + } + + SpinLockRelease(&MyReplicationSlot->mutex); + + /* first write new xmin to disk, so we know what's up after a crash */ + if (updated_xmin || updated_restart) + { + ReplicationSlotMarkDirty(); + ReplicationSlotSave(); + elog(DEBUG1, "updated xmin: %u restart: %u", updated_xmin, updated_restart); + } + + /* + * Now the new xmin is safely on disk, we can let the global value + * advance. We do not take ProcArrayLock or similar since we only + * advance xmin here and there's not much harm done by a concurrent + * computation missing that. + */ + if (updated_xmin) + { + SpinLockAcquire(&MyReplicationSlot->mutex); + MyReplicationSlot->effective_catalog_xmin = MyReplicationSlot->data.catalog_xmin; + SpinLockRelease(&MyReplicationSlot->mutex); + + ReplicationSlotsComputeRequiredXmin(false); + ReplicationSlotsComputeRequiredLSN(); + } + } + else + { + SpinLockAcquire(&MyReplicationSlot->mutex); + MyReplicationSlot->data.confirmed_flush = lsn; + SpinLockRelease(&MyReplicationSlot->mutex); + } +} |