lib/streamaggr: skip empty aggregators (#6307)

Prevent excessive resource usage when stream aggregation config file
contains no matchers by prevent pushing data into Aggregators object.
Before this change a lot of extra work was invoked without reason.

Signed-off-by: hagen1778 <roman@victoriametrics.com>

(cherry picked from commit 7ce052b32d)
Signed-off-by: hagen1778 <roman@victoriametrics.com>

app/vmagent/remotewrite/remotewrite.go

@@ -494,7 +494,7 @@ func tryPush(at *auth.Token, wr *prompbmarshal.WriteRequest, forceDropSamplesOnF
 		}
 		sortLabelsIfNeeded(tssBlock)
 		tssBlock = limitSeriesCardinality(tssBlock)
-		if sas != nil {
+		if sas.IsEnabled() {
 			matchIdxs := matchIdxsPool.Get()
 			matchIdxs.B = sas.Push(tssBlock, matchIdxs.B)
 			if !*streamAggrGlobalKeepInput {
@@ -901,7 +901,7 @@ func (rwctx *remoteWriteCtx) TryPush(tss []prompbmarshal.TimeSeries, forceDropSa
 
 	// Apply stream aggregation or deduplication if they are configured
 	sas := rwctx.sas.Load()
-	if sas != nil {
+	if sas.IsEnabled() {
 		matchIdxs := matchIdxsPool.Get()
 		matchIdxs.B = sas.Push(tss, matchIdxs.B)
 		if !rwctx.streamAggrKeepInput {

docs/CHANGELOG.md

@@ -53,6 +53,7 @@ See also [LTS releases](https://docs.victoriametrics.com/lts-releases/).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent/): prevent potential panic during [stream aggregation](https://docs.victoriametrics.com/stream-aggregation.html) if more than one `--remoteWrite.streamAggr.dedupInterval` is configured. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6205).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent/): skip empty data blocks before sending to the remote write destination. Thanks to @viperstars for [the pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/6241).
 * BUGFIX: [stream aggregation](https://docs.victoriametrics.com/stream-aggregation/): set correct suffix `<output>_prometheus` for aggregation outputs [increase_prometheus](https://docs.victoriametrics.com/stream-aggregation/#increase_prometheus) and [total_prometheus](https://docs.victoriametrics.com/stream-aggregation/#total_prometheus). Before, outputs `total` and `total_prometheus` or `increase` and `increase_prometheus` had the same suffix.
+* BUGFIX: [stream aggregation](https://docs.victoriametrics.com/stream-aggregation/): prevent from excessive resource usage when stream aggregation config file is empty. 
 * BUGFIX: properly estimate the needed memory for query execution if it has the format [`aggr_func`](https://docs.victoriametrics.com/metricsql/#aggregate-functions)([`rollup_func[d]`](https://docs.victoriametrics.com/metricsql/#rollup-functions) (for example, `sum(rate(request_duration_seconds_bucket[5m]))`). This should allow performing aggregations over bigger number of time series when VictoriaMetrics runs in environments with small amounts of available memory. The issue has been introduced in [this commit](https://github.com/VictoriaMetrics/VictoriaMetrics/commit/5138eaeea0791caa34bcfab410e0ca9cd253cd8f) in [v1.83.0](https://docs.victoriametrics.com/changelog_2022/#v1830).
 * BUGFIX: [Single-node VictoriaMetrics](https://docs.victoriametrics.com/) and `vmstorage` in [VictoriaMetrics cluster](https://docs.victoriametrics.com/cluster-victoriametrics/): correctly apply `-inmemoryDataFlushInterval` when it's set to minimum supported value 1s.
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth/): properly release memory used for metrics during config reload. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6247).

lib/streamaggr/streamaggr.go

@@ -294,6 +294,17 @@ func newAggregatorsFromData(data []byte, pushFunc PushFunc, opts *Options) (*Agg
 	}, nil
 }
 
+// IsEnabled returns true if Aggregators has at least one configured aggregator
+func (a *Aggregators) IsEnabled() bool {
+	if a == nil {
+		return false
+	}
+	if len(a.as) == 0 {
+		return false
+	}
+	return true
+}
+
 // MustStop stops a.
 func (a *Aggregators) MustStop() {
 	if a == nil {