memberlist metrics

[pstibrany]

What this PR does:

This PR fixes registration of memberlist_client_kv_store_count metric (this broke in #22) and also disables expiration of internal memberlist-library metrics.

This PR also removes MetricsRegisterer field from memberlist.KVConfig struct in favor of registrerer passed to memberlist.NewKV function.

Which issue(s) this PR fixes:

Fixes #305

Checklist

• Tests updated
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[pracucci]

LGTM. I checked if in Mimir we passed a different registerer (e.g. maybe with different const labels, or so...) between NewKV() and KVConfig.MetricsRegisterer but looks like we don't. I suggest you to do a quick check to Loki and Tempo too before merging tho.

[pstibrany]

LGTM. I checked if in Mimir we passed a different registerer (e.g. maybe with different const labels, or so...) between NewKV() and KVConfig.MetricsRegisterer but looks like we don't. I suggest you to do a quick check to Loki and Tempo too before merging tho.

Loki uses the same reg for both: NewKVInitService and MetricsRegisterer.

[pstibrany]

LGTM. I checked if in Mimir we passed a different registerer (e.g. maybe with different const labels, or so...) between NewKV() and KVConfig.MetricsRegisterer but looks like we don't. I suggest you to do a quick check to Loki and Tempo too before merging tho.

Same is true in Tempo: NewKVInitService and MetricsRegisterer both use the same reg (prometheus.DefaultRegisterer).