add flag to enable and set the mutex profile fraction (cortexproject#1969)

* add flag to enable and set the mutex profile fraction

Signed-off-by: Jacob Lisi <jacob.t.lisi@gmail.com>

* update flag name and update changelog

Signed-off-by: Jacob Lisi <jacob.t.lisi@gmail.com>

Author: jtlisi

CHANGELOG.md

@@ -14,6 +14,7 @@
 * [CHANGE] Ingesters now write only normalised tokens to the ring, although they can still read denormalised tokens used by other ingesters. `-ingester.normalise-tokens` is now deprecated, and ignored. If you want to switch back to using denormalised tokens, you need to downgrade to Cortex 0.4.0. Previous versions don't handle claiming tokens from normalised ingesters correctly. #1809
 * [CHANGE] Overrides mechanism has been renamed to "runtime config", and is now separate from limits. Runtime config is simply a file that is reloaded by Cortex every couple of seconds. Limits and now also multi KV use this mechanism.<br />New arguments were introduced: `-runtime-config.file` (defaults to empty) and `-runtime-config.reload-period` (defaults to 10 seconds), which replace previously used `-limits.per-user-override-config` and `-limits.per-user-override-period` options. Old options are still used if `-runtime-config.file` is not specified. This change is also reflected in YAML configuration, where old `limits.per_tenant_override_config` and `limits.per_tenant_override_period` fields are replaced with `runtime_config.file` and `runtime_config.period` respectively. #1749
 * [FEATURE] The distributor can now drop labels from samples (similar to the removal of the replica label for HA ingestion) per user via the `distributor.drop-label` flag. #1726
+* [FEATURE] Added flag `debug.mutex-profile-fraction` to enable mutex profiling #1969
 * [FEATURE] Added `global` ingestion rate limiter strategy. Deprecated `-distributor.limiter-reload-period` flag. #1766
 * [FEATURE] Added support for Microsoft Azure blob storage to be used for storing chunk data. #1913
 * [FEATURE] Added readiness probe endpoint`/ready` to queriers. #1934

cmd/cortex/main.go

@@ -27,14 +27,20 @@ func init() {
 
 func main() {
 	var (
-		cfg             cortex.Config
-		configFile      = ""
-		eventSampleRate int
-		ballastBytes    int
+		cfg                  cortex.Config
+		configFile           = ""
+		eventSampleRate      int
+		ballastBytes         int
+		mutexProfileFraction int
 	)
 	flag.StringVar(&configFile, "config.file", "", "Configuration file to load.")
 	flag.IntVar(&eventSampleRate, "event.sample-rate", 0, "How often to sample observability events (0 = never).")
 	flag.IntVar(&ballastBytes, "mem-ballast-size-bytes", 0, "Size of memory ballast to allocate.")
+	flag.IntVar(&mutexProfileFraction, "debug.mutex-profile-fraction", 0, "Fraction at which mutex profile vents will be reported, 0 to disable")
+
+	if mutexProfileFraction > 0 {
+		runtime.SetMutexProfileFraction(mutexProfileFraction)
+	}
 
 	flagext.RegisterFlags(&cfg)
 	flag.Parse()