Add dependency on go.uber.org/automaxprocs (#10498)

* add dependency on go.uber.org/automaxprocs

Signed-off-by: Tomas Kohout <tomas.kohout1995@gmail.com>

Co-authored-by: Peter Bourgon <peterbourgon@users.noreply.github.com>
Co-authored-by: Julien Pivotto <roidelapluie@gmail.com>

cmd/prometheus/main.go

@@ -47,6 +47,7 @@ import (
 	toolkit_web "github.com/prometheus/exporter-toolkit/web"
 	toolkit_webflag "github.com/prometheus/exporter-toolkit/web/kingpinflag"
 	"go.uber.org/atomic"
+	"go.uber.org/automaxprocs/maxprocs"
 	kingpin "gopkg.in/alecthomas/kingpin.v2"
 	klog "k8s.io/klog"
 	klogv2 "k8s.io/klog/v2"
@@ -149,6 +150,7 @@ type flagConfig struct {
 	enableExpandExternalLabels bool
 	enableNewSDManager         bool
 	enablePerStepStats         bool
+	enableAutoGOMAXPROCS       bool
 
 	prometheusURL   string
 	corsRegexString string
@@ -186,6 +188,9 @@ func (c *flagConfig) setFeatureListOptions(logger log.Logger) error {
 			case "promql-per-step-stats":
 				c.enablePerStepStats = true
 				level.Info(logger).Log("msg", "Experimental per-step statistics reporting")
+			case "auto-gomaxprocs":
+				c.enableAutoGOMAXPROCS = true
+				level.Info(logger).Log("msg", "Automatically set GOMAXPROCS to match Linux container CPU quota")
 			case "":
 				continue
 			case "promql-at-modifier", "promql-negative-offset":
@@ -382,7 +387,7 @@ func main() {
 	serverOnlyFlag(a, "query.max-samples", "Maximum number of samples a single query can load into memory. Note that queries will fail if they try to load more samples than this into memory, so this also limits the number of samples a query can return.").
 		Default("50000000").IntVar(&cfg.queryMaxSamples)
 
-	a.Flag("enable-feature", "Comma separated feature names to enable. Valid options: agent, exemplar-storage, expand-external-labels, memory-snapshot-on-shutdown, promql-at-modifier, promql-negative-offset, promql-per-step-stats, remote-write-receiver (DEPRECATED), extra-scrape-metrics, new-service-discovery-manager. See https://prometheus.io/docs/prometheus/latest/feature_flags/ for more details.").
+	a.Flag("enable-feature", "Comma separated feature names to enable. Valid options: agent, exemplar-storage, expand-external-labels, memory-snapshot-on-shutdown, promql-at-modifier, promql-negative-offset, promql-per-step-stats, remote-write-receiver (DEPRECATED), extra-scrape-metrics, new-service-discovery-manager, auto-gomaxprocs. See https://prometheus.io/docs/prometheus/latest/feature_flags/ for more details.").
 		Default("").StringsVar(&cfg.featureList)
 
 	promlogflag.AddFlags(a, &cfg.promlogConfig)
@@ -564,6 +569,12 @@ func main() {
 		ruleManager *rules.Manager
 	)
 
+	if cfg.enableAutoGOMAXPROCS {
+		if _, err := maxprocs.Set(); err != nil {
+			level.Warn(logger).Log("msg", "Failed to set GOMAXPROCS automatically", "err", err)
+		}
+	}
+
 	if !agentMode {
 		opts := promql.EngineOpts{
 			Logger:                   log.With(logger, "component", "query engine"),

docs/feature_flags.md

@@ -88,3 +88,12 @@ statistics. Currently this is limited to totalQueryableSamples.
 
 When disabled in either the engine or the query, per-step statistics are not
 computed at all.
+
+## Auto GOMAXPROCS
+
+`--enable-feature=auto-gomaxprocs`
+
+When enabled, GOMAXPROCS variable will be automatically set to match the container CPU limit.
+
+This means that Go runtime will operate as if it had only amount of CPU specified in the container
+CPU limit and not all CPUs on server where it's running.

go.mod

@@ -65,6 +65,7 @@ require (
 	go.opentelemetry.io/otel/sdk v1.4.1
 	go.opentelemetry.io/otel/trace v1.4.1
 	go.uber.org/atomic v1.9.0
+	go.uber.org/automaxprocs v1.4.0
 	go.uber.org/goleak v1.1.12
 	golang.org/x/net v0.0.0-20220225172249-27dd8689420f
 	golang.org/x/oauth2 v0.0.0-20220223155221-ee480838109b

go.sum

@@ -1368,6 +1368,8 @@ go.uber.org/atomic v1.5.0/go.mod h1:sABNBOSYdrvTF6hTgEIbc7YasKWGhgEQZyfxyTvoXHQ=
 go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
 go.uber.org/atomic v1.9.0 h1:ECmE8Bn/WFTYwEW/bpKD3M8VtR/zQVbavAoalC1PYyE=
 go.uber.org/atomic v1.9.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
+go.uber.org/automaxprocs v1.4.0 h1:CpDZl6aOlLhReez+8S3eEotD7Jx0Os++lemPlMULQP0=
+go.uber.org/automaxprocs v1.4.0/go.mod h1:/mTEdr7LvHhs0v7mjdxDreTz1OG5zdZGqgOnhWiR/+Q=
 go.uber.org/goleak v1.1.10/go.mod h1:8a7PlsEVH3e/a/GLqe5IIrQx6GzcnRmZEufDUTk4A7A=
 go.uber.org/goleak v1.1.12 h1:gZAh5/EyT/HQwlpkCy6wTpqfH9H8Lz8zbm3dZh+OyzA=
 go.uber.org/goleak v1.1.12/go.mod h1:cwTWslyiVhfpKIDGSZEM2HlOvcqm+tG4zioyIeLoqMQ=