Enable native histogram for Cortex req duration metric (#6056)

* always enable native histogram for cortex_request_duration_seconds metric

Signed-off-by: Ben Ye <[email protected]>

* update changelog

Signed-off-by: Ben Ye <[email protected]>

---------

Signed-off-by: Ben Ye <[email protected]>

Author: yeya24

Diff for: CHANGELOG.md

@@ -3,6 +3,7 @@
 ## master / unreleased
 * [CHANGE] Upgrade Dockerfile Node version from 14x to 18x. #5906
 * [CHANGE] Ingester: Remove `-querier.query-store-for-labels-enabled` flag. Querying long-term store for labels is always enabled. #5984
+* [CHANGE] Server: Instrument `cortex_request_duration_seconds` metric with native histogram. If `native-histograms` feature is enabled in monitoring Prometheus then the metric name needs to be updated in your dashboards. #6056
 * [FEATURE] Ingester: Experimental: Enable native histogram ingestion via `-blocks-storage.tsdb.enable-native-histograms` flag. #5986
 * [ENHANCEMENT] rulers: Add support to persist tokens in rulers. #5987
 * [ENHANCEMENT] Query Frontend/Querier: Added store gateway postings touched count and touched size in Querier stats and log in Query Frontend. #5892

Diff for: pkg/cortex/cortex.go

@@ -129,6 +129,7 @@ type Config struct {
 func (c *Config) RegisterFlags(f *flag.FlagSet) {
 	c.Server.MetricsNamespace = "cortex"
 	c.Server.ExcludeRequestInLog = true
+	c.Server.MetricsNativeHistogramFactor = 1.1
 
 	// Set the default module list to 'all'
 	c.Target = []string{All}