server: use raftSparseStatus in replica metrics

`Replica.Metrics()` calls `raftStatusRLocked()`, periodically across all
replicas, which is moderately expensive due to deep copies of fields we
don't care about. This patch instead uses `raftSparseStatusRLocked()`
which omits these fields.

Epic: none
Release note: None

pkg/kv/kvserver/replica_metrics.go

@@ -84,7 +84,7 @@ func (r *Replica) Metrics(
 		livenessMap:           livenessMap,
 		clusterNodes:          clusterNodes,
 		desc:                  r.mu.state.Desc,
-		raftStatus:            r.raftStatusRLocked(),
+		raftStatus:            r.raftSparseStatusRLocked(),
 		leaseStatus:           r.leaseStatusAtRLocked(ctx, now),
 		storeID:               r.store.StoreID(),
 		quiescent:             r.mu.quiescent,
@@ -110,7 +110,7 @@ type calcReplicaMetricsInput struct {
 	livenessMap           livenesspb.IsLiveMap
 	clusterNodes          int
 	desc                  *roachpb.RangeDescriptor
-	raftStatus            *raft.Status
+	raftStatus            *raftSparseStatus
 	leaseStatus           kvserverpb.LeaseStatus
 	storeID               roachpb.StoreID
 	quiescent             bool
@@ -138,7 +138,7 @@ func calcReplicaMetrics(d calcReplicaMetricsInput) ReplicaMetrics {
 
 	// The raft leader computes the number of raft entries that replicas are
 	// behind.
-	leader := isRaftLeader(d.raftStatus)
+	leader := d.raftStatus != nil && d.raftStatus.RaftState == raft.StateLeader
 	var leaderBehindCount, leaderPausedFollowerCount int64
 	if leader {
 		leaderBehindCount = calcBehindCount(d.raftStatus, d.desc, d.livenessMap)
@@ -263,7 +263,7 @@ func calcLiveReplicas(repls []roachpb.ReplicaDescriptor, livenessMap livenesspb.
 // calcBehindCount returns a total count of log entries that follower replicas
 // are behind. This can only be computed on the raft leader.
 func calcBehindCount(
-	raftStatus *raft.Status, desc *roachpb.RangeDescriptor, livenessMap livenesspb.IsLiveMap,
+	raftStatus *raftSparseStatus, desc *roachpb.RangeDescriptor, livenessMap livenesspb.IsLiveMap,
 ) int64 {
 	var behindCount int64
 	for _, rd := range desc.Replicas().Descriptors() {

pkg/kv/kvserver/replica_raft.go

@@ -1707,10 +1707,6 @@ func (r *Replica) hasOutstandingSnapshotInFlightToStore(storeID roachpb.StoreID)
 	return r.getSnapshotLogTruncationConstraints(storeID) > 0
 }
 
-func isRaftLeader(raftStatus *raft.Status) bool {
-	return raftStatus != nil && raftStatus.SoftState.RaftState == raft.StateLeader
-}
-
 // HasRaftLeader returns true if the raft group has a raft leader currently.
 func HasRaftLeader(raftStatus *raft.Status) bool {
 	return raftStatus != nil && raftStatus.SoftState.Lead != 0

pkg/kv/kvserver/replica_test.go

@@ -9010,8 +9010,8 @@ func TestReplicaMetrics(t *testing.T) {
 		}
 		return m
 	}
-	status := func(lead uint64, progress map[uint64]tracker.Progress) *raft.Status {
-		status := &raft.Status{
+	status := func(lead uint64, progress map[uint64]tracker.Progress) *raftSparseStatus {
+		status := &raftSparseStatus{
 			Progress: progress,
 		}
 		// The commit index is set so that a progress.Match value of 1 is behind
@@ -9055,7 +9055,7 @@ func TestReplicaMetrics(t *testing.T) {
 		replicas    int32
 		storeID     roachpb.StoreID
 		desc        roachpb.RangeDescriptor
-		raftStatus  *raft.Status
+		raftStatus  *raftSparseStatus
 		liveness    livenesspb.IsLiveMap
 		raftLogSize int64
 		expected    ReplicaMetrics