fix(master): Set the cluster's stop channel to nil upon receiving the signal to prevent it from running again

Signed-off-by: leonrayang <chl696@sina.com>

master/cluster.go

@@ -108,6 +108,7 @@ type Cluster struct {
 	MasterSecretKey []byte
 	retainLogs      uint64
 	stopc           chan bool
+	stopFlag        int32
 	wg              sync.WaitGroup
 
 	ClusterVolSubItem

master/server.go

@@ -23,6 +23,7 @@ import (
 	"regexp"
 	"strconv"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/cubefs/cubefs/proto"
@@ -190,6 +191,10 @@ func (m *Server) Start(cfg *config.Config) (err error) {
 // Shutdown closes the server
 func (m *Server) Shutdown() {
 	var err error
+	if !atomic.CompareAndSwapInt32(&m.cluster.stopFlag, 0, 1) {
+		log.LogWarnf("action[Shutdown] cluster already stopped!")
+		return
+	}
 	if m.cluster.stopc != nil {
 		close(m.cluster.stopc)
 		m.cluster.wg.Wait()