server: add creating raft cluster when become leader.

server/cluster.go

@@ -139,25 +139,32 @@ func (s *Server) getRaftCluster() (*raftCluster, error) {
 		return s.cluster, nil
 	}
 
-	// Find in etcd
+	return nil, nil
+}
+
+func (s *Server) createRaftCluster() error {
+	if s.cluster.IsRunning() {
+		return nil
+	}
+
 	value, err := getValue(s.client, s.getClusterRootPath())
 	if err != nil {
-		return nil, errors.Trace(err)
+		return errors.Trace(err)
 	}
 	if value == nil {
-		return nil, nil
+		return nil
 	}
 
 	clusterMeta := metapb.Cluster{}
 	if err = proto.Unmarshal(value, &clusterMeta); err != nil {
-		return nil, errors.Trace(err)
+		return errors.Trace(err)
 	}
 
 	if err = s.cluster.Start(clusterMeta); err != nil {
-		return nil, errors.Trace(err)
+		return errors.Trace(err)
 	}
 
-	return s.cluster, nil
+	return nil
 }
 
 func encodeRegionSearchKey(endKey []byte) string {

server/cluster_test.go

@@ -336,12 +336,12 @@ func (s *testClusterCacheSuite) TestCache(c *C) {
 
 	cluster, err = s.svr.getRaftCluster()
 	c.Assert(err, IsNil)
+	c.Assert(cluster, IsNil)
 
-	allStores, err := cluster.GetAllStores()
+	allStores, err := s.svr.cluster.GetAllStores()
 	c.Assert(err, IsNil)
 	c.Assert(allStores, HasLen, 2)
 	for _, store := range allStores {
-		_, ok := stores[store.GetId()]
-		c.Assert(ok, IsTrue)
+		c.Assert(stores, HasKey, store.GetId())
 	}
 }

server/conn.go

@@ -61,7 +61,6 @@ func (c *conn) run() {
 			log.Errorf("handle request %s err %v", request, errors.ErrorStack(err))
 			response = NewError(err)
 		}
-
 		if response == nil {
 			// we don't need to response, maybe error?
 			// if error, we will return an error response later.

server/leader.go

@@ -138,7 +138,13 @@ func (s *Server) campaignLeader() error {
 	s.enableLeader(true)
 	defer s.enableLeader(false)
 
-	// keeps the leader
+	// Try to create raft cluster.
+	err = s.createRaftCluster()
+	if err != nil {
+		return errors.Trace(err)
+	}
+
+	// Make the leader keepalived.
 	ch, err := lessor.KeepAlive(s.client.Ctx(), clientv3.LeaseID(leaseResp.ID))
 	if err != nil {
 		return errors.Trace(err)