feat(peer_server): stop service when removed

It doesn't modify the exit logic, but makes external code know
when removal happens and be able to determine what it should do.

etcd/etcd.go

@@ -201,6 +201,14 @@ func (e *Etcd) Run() {
 		// the cluster could be out of work as long as the two nodes cannot transfer messages.
 		e.PeerServer.Start(e.Config.Snapshot, e.Config.Discovery, e.Config.Peers)
 
+		go func() {
+			select {
+			case <-e.PeerServer.StopNotify():
+			case <-e.PeerServer.RemoveNotify():
+				log.Fatal("peer server is removed")
+			}
+		}()
+
 		log.Infof("peer server [name %s, listen on %s, advertised url %s]", e.PeerServer.Config.Name, e.Config.Peer.BindAddr, e.PeerServer.Config.URL)
 		e.peerListener = server.NewListener(psConfig.Scheme, e.Config.Peer.BindAddr, peerTLSConfig)
 

server/peer_server.go

@@ -62,6 +62,8 @@ type PeerServer struct {
 	store          store.Store
 	snapConf       *snapshotConf
 
+	stopNotify           chan bool
+	removeNotify         chan bool
 	closeChan            chan bool
 	routineGroup         sync.WaitGroup
 	timeoutThresholdChan chan interface{}
@@ -261,6 +263,8 @@ func (s *PeerServer) Start(snapshot bool, discoverURL string, peers []string) er
 
 	s.findCluster(discoverURL, peers)
 
+	s.stopNotify = make(chan bool)
+	s.removeNotify = make(chan bool)
 	s.closeChan = make(chan bool)
 
 	s.startRoutine(s.monitorSync)
@@ -279,13 +283,33 @@ func (s *PeerServer) Start(snapshot bool, discoverURL string, peers []string) er
 func (s *PeerServer) Stop() {
 	s.Lock()
 	defer s.Unlock()
-
-	if s.closeChan != nil {
-		close(s.closeChan)
-	}
+	close(s.closeChan)
+	// TODO(yichengq): it should also call async stop for raft server,
+	// but this functionality has not been implemented.
 	s.raftServer.Stop()
 	s.routineGroup.Wait()
-	s.closeChan = nil
+	close(s.stopNotify)
+}
+
+func (s *PeerServer) asyncRemove() {
+	s.Lock()
+	close(s.closeChan)
+	// TODO(yichengq): it should also call async stop for raft server,
+	// but this functionality has not been implemented.
+	go func() {
+		defer s.Unlock()
+		s.raftServer.Stop()
+		s.routineGroup.Wait()
+		close(s.removeNotify)
+	}()
+}
+
+func (s *PeerServer) StopNotify() <-chan bool {
+	return s.stopNotify
+}
+
+func (s *PeerServer) RemoveNotify() <-chan bool {
+	return s.removeNotify
 }
 
 func (s *PeerServer) HTTPHandler() http.Handler {

server/remove_command.go

@@ -2,7 +2,6 @@ package server
 
 import (
 	"encoding/binary"
-	"os"
 
 	"github.com/coreos/etcd/log"
 	"github.com/coreos/etcd/third_party/github.com/goraft/raft"
@@ -65,7 +64,7 @@ func applyRemove(c *RemoveCommand, context raft.Context) (uint64, error) {
 		// command and need to be removed
 		if context.CommitIndex() > ps.joinIndex && ps.joinIndex != 0 {
 			log.Debugf("server [%s] is removed", context.Server().Name())
-			os.Exit(0)
+			ps.asyncRemove()
 		} else {
 			// else ignore remove
 			log.Debugf("ignore previous remove command.")