raft: remove quorum() dependency from readOnly

This now delegates the quorum computation to r.prs, which will allow
it to generalize in a straightforward way when etcd-io/etcd#7625 is
addressed.

raft/progress.go

@@ -320,6 +320,10 @@ func (p *prs) quorum() int {
 	return len(p.nodes)/2 + 1
 }
 
+func (p *prs) hasQuorum(m map[uint64]struct{}) bool {
+	return len(m) >= p.quorum()
+}
+
 // committed returns the largest log index known to be committed based on what
 // the voting members of the group have acknowledged.
 func (p *prs) committed() uint64 {

raft/raft.go

@@ -1000,6 +1000,8 @@ func stepLeader(r *raft, m pb.Message) error {
 			switch r.readOnly.option {
 			case ReadOnlySafe:
 				r.readOnly.addRequest(r.raftLog.committed, m)
+				// The local node automatically acks the request.
+				r.readOnly.recvAck(r.id, m.Entries[0].Data)
 				r.bcastHeartbeatWithCtx(m.Entries[0].Data)
 			case ReadOnlyLeaseBased:
 				ri := r.raftLog.committed
@@ -1097,8 +1099,7 @@ func stepLeader(r *raft, m pb.Message) error {
 			return nil
 		}
 
-		ackCount := r.readOnly.recvAck(m)
-		if ackCount < r.prs.quorum() {
+		if !r.prs.hasQuorum(r.readOnly.recvAck(m.From, m.Context)) {
 			return nil
 		}
 

raft/read_only.go

@@ -50,26 +50,25 @@ func newReadOnly(option ReadOnlyOption) *readOnly {
 // the read only request.
 // `m` is the original read only request message from the local or remote node.
 func (ro *readOnly) addRequest(index uint64, m pb.Message) {
-	ctx := string(m.Entries[0].Data)
-	if _, ok := ro.pendingReadIndex[ctx]; ok {
+	s := string(m.Entries[0].Data)
+	if _, ok := ro.pendingReadIndex[s]; ok {
 		return
 	}
-	ro.pendingReadIndex[ctx] = &readIndexStatus{index: index, req: m, acks: make(map[uint64]struct{})}
-	ro.readIndexQueue = append(ro.readIndexQueue, ctx)
+	ro.pendingReadIndex[s] = &readIndexStatus{index: index, req: m, acks: make(map[uint64]struct{})}
+	ro.readIndexQueue = append(ro.readIndexQueue, s)
 }
 
 // recvAck notifies the readonly struct that the raft state machine received
 // an acknowledgment of the heartbeat that attached with the read only request
 // context.
-func (ro *readOnly) recvAck(m pb.Message) int {
-	rs, ok := ro.pendingReadIndex[string(m.Context)]
+func (ro *readOnly) recvAck(id uint64, context []byte) map[uint64]struct{} {
+	rs, ok := ro.pendingReadIndex[string(context)]
 	if !ok {
-		return 0
+		return nil
 	}
 
-	rs.acks[m.From] = struct{}{}
-	// add one to include an ack from local node
-	return len(rs.acks) + 1
+	rs.acks[id] = struct{}{}
+	return rs.acks
 }
 
 // advance advances the read only request queue kept by the readonly struct.