Enable active series metrics in the ingester by default

CHANGELOG.md

@@ -7,6 +7,7 @@
   - `-alertmanager.receivers-firewall.block.cidr-networks` renamed to `-alertmanager.receivers-firewall-block-cidr-networks`
   - `-alertmanager.receivers-firewall.block.private-addresses` renamed to `-alertmanager.receivers-firewall-block-private-addresses`
 * [CHANGE] Change default value of `-server.grpc.keepalive.min-time-between-pings` to `10s` and `-server.grpc.keepalive.ping-without-stream-allowed` to `true`. #4168
+* [CHANGE] Ingester: Change default value of `-ingester.active-series-metrics-enabled` to `true`. This incurs a small increase in memory usage, between 1.2% and 1.6% as measured on ingesters with 1.3M active series. #4257
 * [FEATURE] Querier: Added new `-querier.max-fetched-series-per-query` flag. When Cortex is running with blocks storage, the max series per query limit is enforced in the querier and applies to unique series received from ingesters and store-gateway (long-term storage). #4179
 * [FEATURE] Querier/Ruler: Added new `-querier.max-fetched-chunk-bytes-per-query` flag. When Cortex is running with blocks storage, the max chunk bytes limit is enforced in the querier and ruler and limits the size of all aggregated chunks returned from ingesters and storage as bytes for a query. #4216
 * [FEATURE] Alertmanager: Added rate-limits to notifiers. Rate limits used by all integrations can be configured using `-alertmanager.notification-rate-limit`, while per-integration rate limits can be specified via `-alertmanager.notification-rate-limit-per-integration` parameter. Both shared and per-integration limits can be overwritten using overrides mechanism. These limits are applied on individual (per-tenant) alertmanagers. Rate-limited notifications are failed notifications. It is possible to monitor rate-limited notifications via new `cortex_alertmanager_notification_rate_limited_total` metric. #4135 #4163

docs/configuration/config-file-reference.md

@@ -776,7 +776,7 @@ lifecycler:
 
 # Enable tracking of active series and export them as metrics.
 # CLI flag: -ingester.active-series-metrics-enabled
-[active_series_metrics_enabled: <boolean> | default = false]
+[active_series_metrics_enabled: <boolean> | default = true]
 
 # How often to update active series metrics.
 # CLI flag: -ingester.active-series-metrics-update-period

pkg/ingester/ingester.go

@@ -122,7 +122,7 @@ func (cfg *Config) RegisterFlags(f *flag.FlagSet) {
 	f.DurationVar(&cfg.MetadataRetainPeriod, "ingester.metadata-retain-period", 10*time.Minute, "Period at which metadata we have not seen will remain in memory before being deleted.")
 
 	f.DurationVar(&cfg.RateUpdatePeriod, "ingester.rate-update-period", 15*time.Second, "Period with which to update the per-user ingestion rates.")
-	f.BoolVar(&cfg.ActiveSeriesMetricsEnabled, "ingester.active-series-metrics-enabled", false, "Enable tracking of active series and export them as metrics.")
+	f.BoolVar(&cfg.ActiveSeriesMetricsEnabled, "ingester.active-series-metrics-enabled", true, "Enable tracking of active series and export them as metrics.")
 	f.DurationVar(&cfg.ActiveSeriesMetricsUpdatePeriod, "ingester.active-series-metrics-update-period", 1*time.Minute, "How often to update active series metrics.")
 	f.DurationVar(&cfg.ActiveSeriesMetricsIdleTimeout, "ingester.active-series-metrics-idle-timeout", 10*time.Minute, "After what time a series is considered to be inactive.")
 	f.BoolVar(&cfg.StreamChunksWhenUsingBlocks, "ingester.stream-chunks-when-using-blocks", false, "Stream chunks when using blocks. This is experimental feature and not yet tested. Once ready, it will be made default and this config option removed.")