Don't abort restore if master is unreachable

go.mod

@@ -21,6 +21,7 @@ require (
 	github.com/golang/mock v1.3.1
 	github.com/golang/protobuf v1.3.2
 	github.com/golang/snappy v0.0.0-20170215233205-553a64147049
+	github.com/google/btree v1.0.0 // indirect
 	github.com/gorilla/websocket v0.0.0-20160912153041-2d1e4548da23
 	github.com/grpc-ecosystem/go-grpc-middleware v1.1.0
 	github.com/grpc-ecosystem/go-grpc-prometheus v1.2.0

go/vt/mysqlctl/builtinbackupengine.go

@@ -367,6 +367,9 @@ func (be *BuiltinBackupEngine) ExecuteBackup(ctx context.Context, params BackupP
 		}
 		if !replicationPosition.Equal(masterPos) {
 			for {
+				if err := ctx.Err(); err != nil {
+					return usable, err
+				}
 				status, err := mysqld.SlaveStatus()
 				if err != nil {
 					return usable, err
@@ -375,6 +378,7 @@ func (be *BuiltinBackupEngine) ExecuteBackup(ctx context.Context, params BackupP
 				if !newPos.Equal(replicationPosition) {
 					break
 				}
+				time.Sleep(1 * time.Second)
 			}
 		}
 	}

go/vt/vttablet/tabletmanager/restore.go

@@ -232,7 +232,12 @@ func (agent *ActionAgent) startReplication(ctx context.Context, pos mysql.Positi
 	defer remoteCancel()
 	posStr, err := tmc.MasterPosition(remoteCtx, ti.Tablet)
 	if err != nil {
-		return vterrors.Wrap(err, "can't get master replication position")
+		// It is possible that though MasterAlias is set, the master tablet is unreachable
+		// Log a warning and let tablet restore in that case
+		// If we had instead considered this fatal, all tablets would crash-loop
+		// until a master appears, which would make it impossible to elect a master.
+		log.Warningf("Can't get master replication position after restore: %v", err)
+		return nil
 	}
 	masterPos, err := mysql.DecodePosition(posStr)
 	if err != nil {
@@ -241,6 +246,9 @@ func (agent *ActionAgent) startReplication(ctx context.Context, pos mysql.Positi
 
 	if !pos.Equal(masterPos) {
 		for {
+			if err := ctx.Err(); err != nil {
+				return err
+			}
 			status, err := agent.MysqlDaemon.SlaveStatus()
 			if err != nil {
 				return vterrors.Wrap(err, "can't get slave status")
@@ -249,6 +257,7 @@ func (agent *ActionAgent) startReplication(ctx context.Context, pos mysql.Positi
 			if !newPos.Equal(pos) {
 				break
 			}
+			time.Sleep(1 * time.Second)
 		}
 	}
 

go/vt/wrangler/testlib/backup_test.go

@@ -108,7 +108,7 @@ func TestBackupRestore(t *testing.T) {
 		},
 	}
 
-	// start master so that slave can fetch master position from it
+	// start master so that replica can fetch master position from it
 	master.StartActionLoop(t, wr)
 	defer master.StopActionLoop(t)
 
@@ -210,3 +210,167 @@ func TestBackupRestore(t *testing.T) {
 	}
 
 }
+
+func TestRestoreUnreachableMaster(t *testing.T) {
+	// Initialize our environment
+	ctx := context.Background()
+	db := fakesqldb.New(t)
+	defer db.Close()
+	ts := memorytopo.NewServer("cell1")
+	wr := wrangler.New(logutil.NewConsoleLogger(), ts, tmclient.NewTabletManagerClient())
+	vp := NewVtctlPipe(t, ts)
+	defer vp.Close()
+
+	// Set up mock query results.
+	db.AddQuery("CREATE DATABASE IF NOT EXISTS _vt", &sqltypes.Result{})
+	db.AddQuery("BEGIN", &sqltypes.Result{})
+	db.AddQuery("COMMIT", &sqltypes.Result{})
+	db.AddQueryPattern(`SET @@session\.sql_log_bin = .*`, &sqltypes.Result{})
+	db.AddQueryPattern(`CREATE TABLE IF NOT EXISTS _vt\.shard_metadata .*`, &sqltypes.Result{})
+	db.AddQueryPattern(`CREATE TABLE IF NOT EXISTS _vt\.local_metadata .*`, &sqltypes.Result{})
+	db.AddQueryPattern(`ALTER TABLE _vt\.local_metadata .*`, &sqltypes.Result{})
+	db.AddQueryPattern(`ALTER TABLE _vt\.shard_metadata .*`, &sqltypes.Result{})
+	db.AddQueryPattern(`UPDATE _vt\.local_metadata SET db_name=.*`, &sqltypes.Result{})
+	db.AddQueryPattern(`UPDATE _vt\.shard_metadata SET db_name=.*`, &sqltypes.Result{})
+	db.AddQueryPattern(`INSERT INTO _vt\.local_metadata .*`, &sqltypes.Result{})
+
+	// Initialize our temp dirs
+	root, err := ioutil.TempDir("", "backuptest")
+	if err != nil {
+		t.Fatalf("os.TempDir failed: %v", err)
+	}
+	defer os.RemoveAll(root)
+
+	// Initialize BackupStorage
+	fbsRoot := path.Join(root, "fbs")
+	*filebackupstorage.FileBackupStorageRoot = fbsRoot
+	*backupstorage.BackupStorageImplementation = "file"
+
+	// Initialize the fake mysql root directories
+	sourceInnodbDataDir := path.Join(root, "source_innodb_data")
+	sourceInnodbLogDir := path.Join(root, "source_innodb_log")
+	sourceDataDir := path.Join(root, "source_data")
+	sourceDataDbDir := path.Join(sourceDataDir, "vt_db")
+	for _, s := range []string{sourceInnodbDataDir, sourceInnodbLogDir, sourceDataDbDir} {
+		if err := os.MkdirAll(s, os.ModePerm); err != nil {
+			t.Fatalf("failed to create directory %v: %v", s, err)
+		}
+	}
+	if err := ioutil.WriteFile(path.Join(sourceInnodbDataDir, "innodb_data_1"), []byte("innodb data 1 contents"), os.ModePerm); err != nil {
+		t.Fatalf("failed to write file innodb_data_1: %v", err)
+	}
+	if err := ioutil.WriteFile(path.Join(sourceInnodbLogDir, "innodb_log_1"), []byte("innodb log 1 contents"), os.ModePerm); err != nil {
+		t.Fatalf("failed to write file innodb_log_1: %v", err)
+	}
+	if err := ioutil.WriteFile(path.Join(sourceDataDbDir, "db.opt"), []byte("db opt file"), os.ModePerm); err != nil {
+		t.Fatalf("failed to write file db.opt: %v", err)
+	}
+
+	// create a master tablet, set its master position
+	master := NewFakeTablet(t, wr, "cell1", 0, topodatapb.TabletType_MASTER, db)
+	master.FakeMysqlDaemon.ReadOnly = false
+	master.FakeMysqlDaemon.Replicating = false
+	master.FakeMysqlDaemon.CurrentMasterPosition = mysql.Position{
+		GTIDSet: mysql.MariadbGTIDSet{
+			mysql.MariadbGTID{
+				Domain:   2,
+				Server:   123,
+				Sequence: 457,
+			},
+		},
+	}
+
+	// start master so that replica can fetch master position from it
+	master.StartActionLoop(t, wr)
+
+	// create a single tablet, set it up so we can do backups
+	// set its position same as that of master so that backup doesn't wait for catchup
+	sourceTablet := NewFakeTablet(t, wr, "cell1", 1, topodatapb.TabletType_REPLICA, db)
+	sourceTablet.FakeMysqlDaemon.ReadOnly = true
+	sourceTablet.FakeMysqlDaemon.Replicating = true
+	sourceTablet.FakeMysqlDaemon.CurrentMasterPosition = mysql.Position{
+		GTIDSet: mysql.MariadbGTIDSet{
+			mysql.MariadbGTID{
+				Domain:   2,
+				Server:   123,
+				Sequence: 457,
+			},
+		},
+	}
+	sourceTablet.FakeMysqlDaemon.ExpectedExecuteSuperQueryList = []string{
+		"STOP SLAVE",
+		"START SLAVE",
+	}
+	sourceTablet.StartActionLoop(t, wr)
+	defer sourceTablet.StopActionLoop(t)
+
+	sourceTablet.Agent.Cnf = &mysqlctl.Mycnf{
+		DataDir:               sourceDataDir,
+		InnodbDataHomeDir:     sourceInnodbDataDir,
+		InnodbLogGroupHomeDir: sourceInnodbLogDir,
+	}
+
+	// run the backup
+	if err := vp.Run([]string{"Backup", topoproto.TabletAliasString(sourceTablet.Tablet.Alias)}); err != nil {
+		t.Fatalf("Backup failed: %v", err)
+	}
+
+	// create a destination tablet, set it up so we can do restores
+	destTablet := NewFakeTablet(t, wr, "cell1", 2, topodatapb.TabletType_REPLICA, db)
+	destTablet.FakeMysqlDaemon.ReadOnly = true
+	destTablet.FakeMysqlDaemon.Replicating = true
+	destTablet.FakeMysqlDaemon.CurrentMasterPosition = mysql.Position{
+		GTIDSet: mysql.MariadbGTIDSet{
+			mysql.MariadbGTID{
+				Domain:   2,
+				Server:   123,
+				Sequence: 457,
+			},
+		},
+	}
+	destTablet.FakeMysqlDaemon.ExpectedExecuteSuperQueryList = []string{
+		"STOP SLAVE",
+		"RESET SLAVE ALL",
+		"FAKE SET SLAVE POSITION",
+		"FAKE SET MASTER",
+		"START SLAVE",
+	}
+	destTablet.FakeMysqlDaemon.FetchSuperQueryMap = map[string]*sqltypes.Result{
+		"SHOW DATABASES": {},
+	}
+	destTablet.FakeMysqlDaemon.SetSlavePositionPos = sourceTablet.FakeMysqlDaemon.CurrentMasterPosition
+	destTablet.FakeMysqlDaemon.SetMasterInput = topoproto.MysqlAddr(master.Tablet)
+
+	destTablet.StartActionLoop(t, wr)
+	defer destTablet.StopActionLoop(t)
+
+	destTablet.Agent.Cnf = &mysqlctl.Mycnf{
+		DataDir:               sourceDataDir,
+		InnodbDataHomeDir:     sourceInnodbDataDir,
+		InnodbLogGroupHomeDir: sourceInnodbLogDir,
+		BinLogPath:            path.Join(root, "bin-logs/filename_prefix"),
+		RelayLogPath:          path.Join(root, "relay-logs/filename_prefix"),
+		RelayLogIndexPath:     path.Join(root, "relay-log.index"),
+		RelayLogInfoPath:      path.Join(root, "relay-log.info"),
+	}
+
+	// stop master so that it is unreachable
+	master.StopActionLoop(t)
+
+	// Restore should still succeed
+	if err := destTablet.Agent.RestoreData(ctx, logutil.NewConsoleLogger(), 0 /* waitForBackupInterval */, false /* deleteBeforeRestore */); err != nil {
+		t.Fatalf("RestoreData failed: %v", err)
+	}
+
+	// verify the full status
+	if err := destTablet.FakeMysqlDaemon.CheckSuperQueryList(); err != nil {
+		t.Errorf("destTablet.FakeMysqlDaemon.CheckSuperQueryList failed: %v", err)
+	}
+	if !destTablet.FakeMysqlDaemon.Replicating {
+		t.Errorf("destTablet.FakeMysqlDaemon.Replicating not set")
+	}
+	if !destTablet.FakeMysqlDaemon.Running {
+		t.Errorf("destTablet.FakeMysqlDaemon.Running not set")
+	}
+
+}