diff options
Diffstat (limited to 'web/api/queries/percentile')
| -rw-r--r-- | web/api/queries/percentile/Makefile.am | 8 | ||||
| -rw-r--r-- | web/api/queries/percentile/README.md | 58 | ||||
| -rw-r--r-- | web/api/queries/percentile/percentile.c | 169 | ||||
| -rw-r--r-- | web/api/queries/percentile/percentile.h | 23 |
4 files changed, 258 insertions, 0 deletions
diff --git a/web/api/queries/percentile/Makefile.am b/web/api/queries/percentile/Makefile.am new file mode 100644 index 000000000..161784b8f --- /dev/null +++ b/web/api/queries/percentile/Makefile.am @@ -0,0 +1,8 @@ +# 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/percentile/README.md b/web/api/queries/percentile/README.md new file mode 100644 index 000000000..70afc7420 --- /dev/null +++ b/web/api/queries/percentile/README.md @@ -0,0 +1,58 @@ +<!-- +title: "Percentile" +description: "Use percentile in API queries and health entities to find the 'percentile' value from a sample, eliminating any unwanted spikes in the returned metrics." +custom_edit_url: https://github.com/netdata/netdata/edit/master/web/api/queries/percentile/README.md +--> + +# Percentile + +The percentile is the average value of a series using only the smaller N percentile of the values. +(a population or a probability distribution). + +Netdata applies linear interpolation on the last point, if the percentile requested does not give a round number of +points. + +The following percentile aliases are defined: + +- `percentile25` +- `percentile50` +- `percentile75` +- `percentile80` +- `percentile90` +- `percentile95` +- `percentile97` +- `percentile98` +- `percentile99` + +The default `percentile` is an alias for `percentile95`. +Any percentile may be requested using the `group_options` query parameter. + +## how to use + +Use it in alarms like this: + +``` + alarm: my_alarm + on: my_chart +lookup: percentile95 -1m unaligned of my_dimension + warn: $this > 1000 +``` + +`percentile` 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=percentile` in the URL and the additional parameter `group_options` +may be used to request any percentile (e.g. `&group=percentile&group_options=96`). + +## Examples + +Examining last 1 minute `successful` web server responses: + +-  +-  +-  +-  + +## References + +- <https://en.wikipedia.org/wiki/Percentile>. diff --git a/web/api/queries/percentile/percentile.c b/web/api/queries/percentile/percentile.c new file mode 100644 index 000000000..88f8600dd --- /dev/null +++ b/web/api/queries/percentile/percentile.c @@ -0,0 +1,169 @@ +// SPDX-License-Identifier: GPL-3.0-or-later + +#include "percentile.h" + +// ---------------------------------------------------------------------------- +// median + +struct grouping_percentile { + size_t series_size; + size_t next_pos; + NETDATA_DOUBLE percent; + + NETDATA_DOUBLE *series; +}; + +static void grouping_create_percentile_internal(RRDR *r, const char *options, NETDATA_DOUBLE def) { + long entries = r->group; + if(entries < 10) entries = 10; + + struct grouping_percentile *g = (struct grouping_percentile *)onewayalloc_callocz(r->internal.owa, 1, sizeof(struct grouping_percentile)); + g->series = onewayalloc_mallocz(r->internal.owa, entries * sizeof(NETDATA_DOUBLE)); + g->series_size = (size_t)entries; + + g->percent = def; + if(options && *options) { + g->percent = str2ndd(options, NULL); + if(!netdata_double_isnumber(g->percent)) g->percent = 0.0; + if(g->percent < 0.0) g->percent = 0.0; + if(g->percent > 100.0) g->percent = 100.0; + } + + g->percent = g->percent / 100.0; + r->internal.grouping_data = g; +} + +void grouping_create_percentile25(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 25.0); +} +void grouping_create_percentile50(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 50.0); +} +void grouping_create_percentile75(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 75.0); +} +void grouping_create_percentile80(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 80.0); +} +void grouping_create_percentile90(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 90.0); +} +void grouping_create_percentile95(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 95.0); +} +void grouping_create_percentile97(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 97.0); +} +void grouping_create_percentile98(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 98.0); +} +void grouping_create_percentile99(RRDR *r, const char *options) { + grouping_create_percentile_internal(r, options, 99.0); +} + +// resets when switches dimensions +// so, clear everything to restart +void grouping_reset_percentile(RRDR *r) { + struct grouping_percentile *g = (struct grouping_percentile *)r->internal.grouping_data; + g->next_pos = 0; +} + +void grouping_free_percentile(RRDR *r) { + struct grouping_percentile *g = (struct grouping_percentile *)r->internal.grouping_data; + if(g) onewayalloc_freez(r->internal.owa, g->series); + + onewayalloc_freez(r->internal.owa, r->internal.grouping_data); + r->internal.grouping_data = NULL; +} + +void grouping_add_percentile(RRDR *r, NETDATA_DOUBLE value) { + struct grouping_percentile *g = (struct grouping_percentile *)r->internal.grouping_data; + + if(unlikely(g->next_pos >= g->series_size)) { + g->series = onewayalloc_doublesize( r->internal.owa, g->series, g->series_size * sizeof(NETDATA_DOUBLE)); + g->series_size *= 2; + } + + g->series[g->next_pos++] = value; +} + +NETDATA_DOUBLE grouping_flush_percentile(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr) { + struct grouping_percentile *g = (struct grouping_percentile *)r->internal.grouping_data; + + NETDATA_DOUBLE value; + size_t available_slots = g->next_pos; + + if(unlikely(!available_slots)) { + value = 0.0; + *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; + } + else if(available_slots == 1) { + value = g->series[0]; + } + else { + sort_series(g->series, available_slots); + + NETDATA_DOUBLE min = g->series[0]; + NETDATA_DOUBLE max = g->series[available_slots - 1]; + + if (min != max) { + size_t slots_to_use = (size_t)((NETDATA_DOUBLE)available_slots * g->percent); + if(!slots_to_use) slots_to_use = 1; + + NETDATA_DOUBLE percent_to_use = (NETDATA_DOUBLE)slots_to_use / (NETDATA_DOUBLE)available_slots; + NETDATA_DOUBLE percent_delta = g->percent - percent_to_use; + + NETDATA_DOUBLE percent_interpolation_slot = 0.0; + NETDATA_DOUBLE percent_last_slot = 0.0; + if(percent_delta > 0.0) { + NETDATA_DOUBLE percent_to_use_plus_1_slot = (NETDATA_DOUBLE)(slots_to_use + 1) / (NETDATA_DOUBLE)available_slots; + NETDATA_DOUBLE percent_1slot = percent_to_use_plus_1_slot - percent_to_use; + + percent_interpolation_slot = percent_delta / percent_1slot; + percent_last_slot = 1 - percent_interpolation_slot; + } + + int start_slot, stop_slot, step, last_slot, interpolation_slot; + if(min >= 0.0 && max >= 0.0) { + start_slot = 0; + stop_slot = start_slot + (int)slots_to_use; + last_slot = stop_slot - 1; + interpolation_slot = stop_slot; + step = 1; + } + else { + start_slot = (int)available_slots - 1; + stop_slot = start_slot - (int)slots_to_use; + last_slot = stop_slot + 1; + interpolation_slot = stop_slot; + step = -1; + } + + value = 0.0; + for(int slot = start_slot; slot != stop_slot ; slot += step) + value += g->series[slot]; + + size_t counted = slots_to_use; + if(percent_interpolation_slot > 0.0 && interpolation_slot >= 0 && interpolation_slot < (int)available_slots) { + value += g->series[interpolation_slot] * percent_interpolation_slot; + value += g->series[last_slot] * percent_last_slot; + counted++; + } + + value = value / (NETDATA_DOUBLE)counted; + } + else + value = min; + } + + if(unlikely(!netdata_double_isnumber(value))) { + value = 0.0; + *rrdr_value_options_ptr |= RRDR_VALUE_EMPTY; + } + + //log_series_to_stderr(g->series, g->next_pos, value, "percentile"); + + g->next_pos = 0; + + return value; +} diff --git a/web/api/queries/percentile/percentile.h b/web/api/queries/percentile/percentile.h new file mode 100644 index 000000000..709717ebd --- /dev/null +++ b/web/api/queries/percentile/percentile.h @@ -0,0 +1,23 @@ +// SPDX-License-Identifier: GPL-3.0-or-later + +#ifndef NETDATA_API_QUERIES_PERCENTILE_H +#define NETDATA_API_QUERIES_PERCENTILE_H + +#include "../query.h" +#include "../rrdr.h" + +extern void grouping_create_percentile25(RRDR *r, const char *options); +extern void grouping_create_percentile50(RRDR *r, const char *options); +extern void grouping_create_percentile75(RRDR *r, const char *options); +extern void grouping_create_percentile80(RRDR *r, const char *options); +extern void grouping_create_percentile90(RRDR *r, const char *options); +extern void grouping_create_percentile95(RRDR *r, const char *options); +extern void grouping_create_percentile97(RRDR *r, const char *options); +extern void grouping_create_percentile98(RRDR *r, const char *options); +extern void grouping_create_percentile99(RRDR *r, const char *options ); +extern void grouping_reset_percentile(RRDR *r); +extern void grouping_free_percentile(RRDR *r); +extern void grouping_add_percentile(RRDR *r, NETDATA_DOUBLE value); +extern NETDATA_DOUBLE grouping_flush_percentile(RRDR *r, RRDR_VALUE_FLAGS *rrdr_value_options_ptr); + +#endif //NETDATA_API_QUERIES_PERCENTILE_H |