4 files changed, 121 insertions, 0 deletions
diff --git a/web/api/queries/max/Makefile.am b/web/api/queries/max/Makefile.am
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+++ b/web/api/queries/max/Makefile.am
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+# SPDX-License-Identifier: GPL-3.0-or-later
+
+AUTOMAKE_OPTIONS = subdir-objects
+MAINTAINERCLEANFILES = $(srcdir)/Makefile.in
+
+dist_noinst_DATA = \
+    README.md \
+    $(NULL)
diff --git a/web/api/queries/max/README.md b/web/api/queries/max/README.md
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+++ b/web/api/queries/max/README.md
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+<!--
+title: "Max"
+custom_edit_url: https://github.com/netdata/netdata/edit/master/web/api/queries/max/README.md
+-->
+
+# Max
+
+This module finds the max value in the time-frame given.
+
+## how to use
+
+Use it in alarms like this:
+
+```
+ alarm: my_alarm
+    on: my_chart
+lookup: max -1m unaligned of my_dimension
+  warn: $this > 1000
+```
+
+`max` does not change the units. For example, if the chart units is `requests/sec`, the result
+will be again expressed in the same units. 
+
+It can also be used in APIs and badges as `&group=max` in the URL.
+
+## Examples
+
+Examining last 1 minute `successful` web server responses:
+
+-   ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=min&after=-60&label=min)
+-   ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=average&after=-60&label=average)
+-   ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=max&after=-60&label=max&value_color=orange)
+
+## References
+
+-   <https://en.wikipedia.org/wiki/Sample_maximum_and_minimum>.
+
+[![analytics](https://www.google-analytics.com/collect?v=1&aip=1&t=pageview&_s=1&ds=github&dr=https%3A%2F%2Fgithub.com%2Fnetdata%2Fnetdata&dl=https%3A%2F%2Fmy-netdata.io%2Fgithub%2Fweb%2Fapi%2Fqueries%2Fmax%2FREADME&_u=MAC~&cid=5792dfd7-8dc4-476b-af31-da2fdb9f93d2&tid=UA-64295674-3)](<>)
diff --git a/web/api/queries/max/max.c b/web/api/queries/max/max.c
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+++ b/web/api/queries/max/max.c
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+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "max.h"
+
+// ----------------------------------------------------------------------------
+// max
+
+struct grouping_max {
+    calculated_number max;
+    size_t count;
+};
+
+void *grouping_create_max(RRDR *r) {
+    (void)r;
+    return callocz(1, sizeof(struct grouping_max));
+}
+
+// resets when switches dimensions
+// so, clear everything to restart
+void grouping_reset_max(RRDR *r) {
+    struct grouping_max *g = (struct grouping_max *)r->internal.grouping_data;
+    g->max = 0;
+    g->count = 0;
+}
+
+void grouping_free_max(RRDR *r) {
+    freez(r->internal.grouping_data);
+    r->internal.grouping_data = NULL;
+}
+
+void grouping_add_max(RRDR *r, calculated_number value) {
+    if(!isnan(value)) {
+        struct grouping_max *g = (struct grouping_max *)r->internal.grouping_data;
+
+        if(!g->count || calculated_number_fabs(value) > calculated_number_fabs(g->max)) {
+            g->max = value;
+            g->count++;
+        }
+    }
+}
+
+calculated_number grouping_flush_max(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) {
+    struct grouping_max *g = (struct grouping_max *)r->internal.grouping_data;
+
+    calculated_number value;
+
+    if(unlikely(!g->count)) {
+        value = 0.0;
+        *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
+    }
+    else {
+        value = g->max;
+    }
+
+    g->max = 0.0;
+    g->count = 0;
+
+    return value;
+}
+
diff --git a/web/api/queries/max/max.h b/web/api/queries/max/max.h
new file mode 100644
index 0000000..d839fe3
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+++ b/web/api/queries/max/max.h
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+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_API_QUERY_MAX_H
+#define NETDATA_API_QUERY_MAX_H
+
+#include "../query.h"
+#include "../rrdr.h"
+
+extern void *grouping_create_max(RRDR *r);
+extern void grouping_reset_max(RRDR *r);
+extern void grouping_free_max(RRDR *r);
+extern void grouping_add_max(RRDR *r, calculated_number value);
+extern calculated_number grouping_flush_max(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr);
+
+#endif //NETDATA_API_QUERY_MAX_H