modularize the query api (#4443)

* modularized exporters

* modularized API data queries

* optimized queries

* modularized API data reduction methods

* modularized api queries

* added new directories in makefiles

* added median db query

* moved all RRDR_GROUPING related to query.h

* added stddev query

* operational median and stddev

* working simple exponential smoothing

* too complex to do it right

* fixed ses

* fixed ses

* rewrote query engine

* fix double-exponential-smoothing

* cleanup

* fixed bug identified by @vlvkobal at rrdset_first_slot()

* enable freeipmi on systems with libipmimonitoring; #4440

1 files changed, 73 insertions, 0 deletions

diff --git a/web/api/queries/stddev/stddev.c b/web/api/queries/stddev/stddev.c
new file mode 100644
index 0000000000..e88a853740
--- /dev/null
+++ b/web/api/queries/stddev/stddev.c
@@ -0,0 +1,73 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "stddev.h"
+
+
+// ----------------------------------------------------------------------------
+// stddev
+
+struct grouping_stddev {
+    size_t series_size;
+    size_t next_pos;
+
+    LONG_DOUBLE series[];
+};
+
+void *grouping_init_stddev(RRDR *r) {
+    long entries = (r->group > r->group_points) ? r->group : r->group_points;
+    if(entries < 0) entries = 0;
+
+    struct grouping_stddev *g = (struct grouping_stddev *)callocz(1, sizeof(struct grouping_stddev) + entries * sizeof(LONG_DOUBLE));
+    g->series_size = (size_t)entries;
+
+    return g;
+}
+
+// resets when switches dimensions
+// so, clear everything to restart
+void grouping_reset_stddev(RRDR *r) {
+    struct grouping_stddev *g = (struct grouping_stddev *)r->grouping_data;
+    g->next_pos = 0;
+}
+
+void grouping_free_stddev(RRDR *r) {
+    freez(r->grouping_data);
+}
+
+void grouping_add_stddev(RRDR *r, calculated_number value) {
+    struct grouping_stddev *g = (struct grouping_stddev *)r->grouping_data;
+
+    if(unlikely(g->next_pos >= g->series_size)) {
+        error("INTERNAL ERROR: stddev buffer overflow on chart '%s' - next_pos = %zu, series_size = %zu, r->group = %ld, r->group_points = %ld.", r->st->name, g->next_pos, g->series_size, r->group, r->group_points);
+    }
+    else {
+        if(isnormal(value))
+            g->series[g->next_pos++] = (LONG_DOUBLE)value;
+    }
+}
+
+calculated_number grouping_flush_stddev(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) {
+    struct grouping_stddev *g = (struct grouping_stddev *)r->grouping_data;
+
+    calculated_number value;
+
+    if(unlikely(!g->next_pos)) {
+        value = 0.0;
+        *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
+    }
+    else {
+        value = standard_deviation(g->series, g->next_pos);
+
+        if(!isnormal(value)) {
+            value = 0.0;
+            *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY;
+        }
+
+        //log_series_to_stderr(g->series, g->next_pos, value, "stddev");
+    }
+
+    g->next_pos = 0;
+
+    return  value;
+}
+