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lib/storage: improve performance for /api/v1/labels and /api/v1/label/.../values endpoints when match[] filter matches small number of time series

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Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2978
This commit is contained in:
Aliaksandr Valialkin 2022-08-16 13:32:30 +03:00
parent e0e7c14788
commit f830edc0bc
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2 changed files with 83 additions and 6 deletions
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1
docs/CHANGELOG.md
View file

@ -29,6 +29,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
* FEATURE: [vmalert](https://docs.victoriametrics.com/vmalert.html): add `toTime()` template function in the same way as Prometheus 2.38 [does](https://github.com/prometheus/prometheus/pull/10993). See [these docs](https://prometheus.io/docs/prometheus/latest/configuration/template_reference/#numbers).
* BUGFIX: prevent from excess CPU usage when the storage enters [read-only mode](https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html#readonly-mode).
* BUGFIX: improve performance for requests to [/api/v1/labels](https://docs.victoriametrics.com/url-examples.html#apiv1labels) and [/api/v1/label/.../values](https://docs.victoriametrics.com/url-examples.html#apiv1labelvalues) when the filter in the `match[]` query arg matches small number of time series. The performance for this case has been reduced in [v1.78.0](https://docs.victoriametrics.com/CHANGELOG.html#v1780). See [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2978) and [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1533) issues.
## [v1.80.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.80.0)

88
lib/storage/index_db.go
View file

@ -850,9 +850,13 @@ func (is *indexSearch) searchLabelNamesWithFiltersOnDate(qt *querytracer.Tracer,
if err != nil {
return err
}
if filter != nil && filter.Len() == 0 {
qt.Printf("found zero label names for filter=%s", tfss)
return nil
if filter != nil && filter.Len() <= 100e3 {
// It is faster to obtain label names by metricIDs from the filter
// instead of scanning the inverted index for the matching filters.
// This hould help https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2978
metricIDs := filter.AppendTo(nil)
qt.Printf("sort %d metricIDs", len(metricIDs))
return is.getLabelNamesForMetricIDs(qt, metricIDs, lns, maxLabelNames)
}
var prevLabelName []byte
ts := &is.ts
@ -912,6 +916,41 @@ func (is *indexSearch) searchLabelNamesWithFiltersOnDate(qt *querytracer.Tracer,
return nil
}
func (is *indexSearch) getLabelNamesForMetricIDs(qt *querytracer.Tracer, metricIDs []uint64, lns map[string]struct{}, maxLabelNames int) error {
lns["__name__"] = struct{}{}
var mn MetricName
foundLabelNames := 0
var buf []byte
for _, metricID := range metricIDs {
var err error
buf, err = is.searchMetricNameWithCache(buf[:0], metricID)
if err != nil {
if err == io.EOF {
// It is likely the metricID->metricName entry didn't propagate to inverted index yet.
// Skip this metricID for now.
continue
}
return fmt.Errorf("cannot find metricName by metricID %d: %w", metricID, err)
}
if err := mn.Unmarshal(buf); err != nil {
return fmt.Errorf("cannot unmarshal metricName %q: %w", buf, err)
}
for _, tag := range mn.Tags {
_, ok := lns[string(tag.Key)]
if !ok {
foundLabelNames++
lns[string(tag.Key)] = struct{}{}
if len(lns) >= maxLabelNames {
qt.Printf("hit the limit on the number of unique label names: %d", maxLabelNames)
return nil
}
}
}
}
qt.Printf("get %d distinct label names from %d metricIDs", foundLabelNames, len(metricIDs))
return nil
}
// SearchLabelValuesWithFiltersOnTimeRange returns label values for the given labelName, tfss and tr.
func (db *indexDB) SearchLabelValuesWithFiltersOnTimeRange(qt *querytracer.Tracer, labelName string, tfss []*TagFilters, tr TimeRange,
maxLabelValues, maxMetrics int, deadline uint64) ([]string, error) {
@ -1007,9 +1046,13 @@ func (is *indexSearch) searchLabelValuesWithFiltersOnDate(qt *querytracer.Tracer
if err != nil {
return err
}
if filter != nil && filter.Len() == 0 {
qt.Printf("found zero label values for filter=%s", tfss)
return nil
if filter != nil && filter.Len() < 100e3 {
// It is faster to obtain label names by metricIDs from the filter
// instead of scanning the inverted index for the matching filters.
// This hould help https://github.com/VictoriaMetrics/VictoriaMetrics/issues/2978
metricIDs := filter.AppendTo(nil)
qt.Printf("sort %d metricIDs", len(metricIDs))
return is.getLabelValuesForMetricIDs(qt, lvs, labelName, metricIDs, maxLabelValues)
}
if labelName == "__name__" {
// __name__ label is encoded as empty string in indexdb.
@ -1068,6 +1111,39 @@ func (is *indexSearch) searchLabelValuesWithFiltersOnDate(qt *querytracer.Tracer
return nil
}
func (is *indexSearch) getLabelValuesForMetricIDs(qt *querytracer.Tracer, lvs map[string]struct{}, labelName string, metricIDs []uint64, maxLabelValues int) error {
var mn MetricName
foundLabelValues := 0
var buf []byte
for _, metricID := range metricIDs {
var err error
buf, err = is.searchMetricNameWithCache(buf[:0], metricID)
if err != nil {
if err == io.EOF {
// It is likely the metricID->metricName entry didn't propagate to inverted index yet.
// Skip this metricID for now.
continue
}
return fmt.Errorf("cannot find metricName by metricID %d: %w", metricID, err)
}
if err := mn.Unmarshal(buf); err != nil {
return fmt.Errorf("cannot unmarshal metricName %q: %w", buf, err)
}
tagValue := mn.GetTagValue(labelName)
_, ok := lvs[string(tagValue)]
if !ok {
foundLabelValues++
lvs[string(tagValue)] = struct{}{}
if len(lvs) >= maxLabelValues {
qt.Printf("hit the limit on the number of unique label values for label %q: %d", labelName, maxLabelValues)
return nil
}
}
}
qt.Printf("get %d distinct values for label %q from %d metricIDs", foundLabelValues, labelName, len(metricIDs))
return nil
}
// SearchTagValueSuffixes returns all the tag value suffixes for the given tagKey and tagValuePrefix on the given tr.
//
// This allows implementing https://graphite-api.readthedocs.io/en/latest/api.html#metrics-find or similar APIs.