server: use the same initcluster to restart joined member

pkg/integration_test/join_test.go

@@ -15,6 +15,7 @@ package integration
 
 import (
 	"context"
+	"os"
 	"time"
 
 	. "github.com/pingcap/check"
@@ -44,6 +45,8 @@ func (s *integrationTestSuite) TestSimpleJoin(c *C) {
 	c.Assert(err, IsNil)
 	err = pd2.Run(context.TODO())
 	c.Assert(err, IsNil)
+	_, err = os.Stat(pd2.GetConfig().DataDir + "/join")
+	c.Assert(os.IsNotExist(err), IsFalse)
 	members, err = etcdutil.ListEtcdMembers(client)
 	c.Assert(err, IsNil)
 	c.Assert(members.Members, HasLen, 2)
@@ -57,6 +60,8 @@ func (s *integrationTestSuite) TestSimpleJoin(c *C) {
 	c.Assert(err, IsNil)
 	err = pd3.Run(context.TODO())
 	c.Assert(err, IsNil)
+	_, err = os.Stat(pd3.GetConfig().DataDir + "/join")
+	c.Assert(os.IsNotExist(err), IsFalse)
 	members, err = etcdutil.ListEtcdMembers(client)
 	c.Assert(err, IsNil)
 	c.Assert(members.Members, HasLen, 3)

server/join.go

@@ -15,6 +15,7 @@ package server
 
 import (
 	"fmt"
+	"io/ioutil"
 	"os"
 	"path"
 	"strings"
@@ -26,6 +27,15 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
+const (
+	// privateFileMode grants owner to read/write a file.
+	privateFileMode = 0600
+	// privateDirMode grants owner to make/remove files inside the directory.
+	privateDirMode = 0700
+
+	retryTimes = 100
+)
+
 // PrepareJoinCluster sends MemberAdd command to PD cluster,
 // and returns the initial configuration of the PD cluster.
 //
@@ -73,8 +83,20 @@ func PrepareJoinCluster(cfg *Config) error {
 		return errors.New("join self is forbidden")
 	}
 
-	// Cases with data directory.
+	filePath := cfg.DataDir + "/join"
+	// Read the persist join config
+	if _, err := os.Stat(filePath); !os.IsNotExist(err) {
+		s, err := ioutil.ReadFile(filePath)
+		if err != nil {
+			log.Fatal("read the join config meet error: ", err)
+		}
+		cfg.InitialCluster = strings.TrimSpace(string(s))
+		cfg.InitialClusterState = embed.ClusterStateFlagExisting
+		return nil
+	}
+
 	initialCluster := ""
+	// Cases with data directory.
 	if isDataExist(path.Join(cfg.DataDir, "member")) {
 		cfg.InitialCluster = initialCluster
 		cfg.InitialClusterState = embed.ClusterStateFlagExisting
@@ -138,7 +160,20 @@ func PrepareJoinCluster(cfg *Config) error {
 	initialCluster = strings.Join(pds, ",")
 	cfg.InitialCluster = initialCluster
 	cfg.InitialClusterState = embed.ClusterStateFlagExisting
-	return nil
+	err = os.Mkdir(cfg.DataDir, privateDirMode)
+	if err != nil && !os.IsExist(err) {
+		return err
+	}
+
+	for i := 0; i < retryTimes; i++ {
+		err = ioutil.WriteFile(filePath, []byte(cfg.InitialCluster), privateFileMode)
+		if err != nil {
+			log.Errorf("persist join config failed: %s", err)
+			continue
+		}
+		break
+	}
+	return err
 }
 
 func isDataExist(d string) bool {