feat(metarepos): add metric for count of commit result history

This patch defines metrics for count of commif result hostory.

Author: hungryjang

internal/metarepos/metadata_repository_metrics.go

@@ -11,6 +11,7 @@ type metricsBag struct {
 	requests metric.Int64UpDownCounter
 	records  sync.Map
 	counts   sync.Map
+	gauges   sync.Map
 }
 
 func newMetricsBag(mt metric.Meter) *metricsBag {
@@ -44,8 +45,21 @@ func (mb *metricsBag) Counts(name string) metric.Int64Counter {
 		if err != nil {
 			panic(err)
 		}
-		f, _ = mb.records.LoadOrStore(name, r)
+		f, _ = mb.counts.LoadOrStore(name, r)
 	}
 
 	return f.(metric.Int64Counter)
 }
+
+func (mb *metricsBag) Gauges(name string) metric.Int64Gauge {
+	f, ok := mb.gauges.Load(name)
+	if !ok {
+		r, err := mb.mt.Int64Gauge(name)
+		if err != nil {
+			panic(err)
+		}
+		f, _ = mb.gauges.LoadOrStore(name, r)
+	}
+
+	return f.(metric.Int64Gauge)
+}

internal/metarepos/raft_metadata_repository.go

@@ -965,6 +965,9 @@ func (mr *RaftMetadataRepository) applyCommit(r *mrpb.Commit, appliedIndex uint6
 			mr.storage.TrimLogStreamCommitHistory(trimVer) //nolint:errcheck,revive // TODO:: Handle an error returned.
 		}
 
+		mr.tmStub.mb.Gauges("mr.commit.history.count").Record(ctx,
+			int64(mr.storage.getLastCommitResultsNoLock().GetVersion())-int64(mr.storage.getFirstCommitResultsNoLock().GetVersion())+1)
+
 		mr.reportCollector.Commit()
 
 		// TODO:: trigger next commit