Delay the monitorStorageVersion goroutine until the server is fully ready

Signed-off-by: Benjamin Wang <benjamin.ahrtr@gmail.com>

Author: ahrtr

server/embed/serve.go

@@ -16,6 +16,7 @@ package embed
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	defaultLog "log"
@@ -100,7 +101,12 @@ func (sctx *serveCtx) serve(
 	gopts ...grpc.ServerOption,
 ) (err error) {
 	logger := defaultLog.New(io.Discard, "etcdhttp", 0)
-	<-s.ReadyNotify()
+
+	select {
+	case <-s.StoppingNotify():
+		return errors.New("server is stopping")
+	case <-s.ReadyNotify():
+	}
 
 	sctx.lg.Info("ready to serve client requests")
 

server/etcdserver/server.go

@@ -2284,6 +2284,21 @@ func (s *EtcdServer) monitorClusterVersions() {
 func (s *EtcdServer) monitorStorageVersion() {
 	lg := s.Logger()
 	monitor := serverversion.NewMonitor(lg, NewServerVersionAdapter(s))
+
+	// The field "storageVersion" in Meta bucket was introduced in 3.6.
+	// It doesn't exist in 3.5 and older versions. We depend on fields
+	// "confState" and "term" to identify 3.5, as the two fields were
+	// introduced in 3.5.
+	// But the field "confState" is only guaranteed to be populated
+	// after the member fully bootstraps itself. So we need to wait
+	// for the etcdserver ready for serve client requests here.
+	select {
+	case <-s.StoppingNotify():
+		return
+	case <-s.ReadyNotify():
+	}
+	lg.Info("monitorStorageVersion: start running")
+
 	for {
 		select {
 		case <-time.After(monitorVersionInterval):