[release-21.0] Fix panic in vttablet when closing topo server twice (#…

…17094) (#17122)

Co-authored-by: vitess-bot[bot] <108069721+vitess-bot[bot]@users.noreply.github.com>

go/cmd/vttablet/cli/cli.go

@@ -143,7 +143,6 @@ func run(cmd *cobra.Command, args []string) error {
 
 	qsc, err := createTabletServer(ctx, env, config, ts, tabletAlias, srvTopoCounts)
 	if err != nil {
-		ts.Close()
 		return err
 	}
 
@@ -172,7 +171,6 @@ func run(cmd *cobra.Command, args []string) error {
 		VDiffEngine:         vdiff.NewEngine(ts, tablet, env.CollationEnv(), env.Parser()),
 	}
 	if err := tm.Start(tablet, config); err != nil {
-		ts.Close()
 		return fmt.Errorf("failed to parse --tablet-path or initialize DB credentials: %w", err)
 	}
 	servenv.OnClose(func() {

go/cmd/vttablet/cli/cli_test.go

@@ -0,0 +1,58 @@
+/*
+Copyright 2024 The Vitess Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package cli
+
+import (
+	"context"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"vitess.io/vitess/go/vt/topo"
+	"vitess.io/vitess/go/vt/topo/memorytopo"
+)
+
+// TestRunFailsToStartTabletManager tests the code path in 'run' where we fail to start the TabletManager
+// this is done by starting vttablet without a cnf file but requesting it to restore from backup.
+// When starting, the TabletManager checks if it needs to restore, in tm.handleRestore but this step will
+// fail if we do not provide a cnf file and if the flag --restore_from_backup is provided.
+func TestRunFailsToStartTabletManager(t *testing.T) {
+	ts, factory := memorytopo.NewServerAndFactory(context.Background(), "cell")
+	topo.RegisterFactory("test", factory)
+
+	args := append([]string{}, os.Args...)
+	t.Cleanup(func() {
+		ts.Close()
+		tabletPath = ""
+		os.Args = append([]string{}, args...)
+	})
+
+	os.Args = []string{"vttablet",
+		"--topo_implementation", "test", "--topo_global_server_address", "localhost", "--topo_global_root", "cell",
+		"--db_host", "localhost", "--db_port", "3306",
+		"--tablet-path", "cell-1", "--init_keyspace", "ks", "--init_shard", "0", "--init_tablet_type", "replica",
+		"--restore_from_backup",
+	}
+
+	// Creating and canceling the context so that pending tasks in tm_init gets canceled before we close the topo server
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	err := Main.ExecuteContext(ctx)
+	require.ErrorContains(t, err, "you cannot enable --restore_from_backup without a my.cnf file")
+}

go/vt/topo/server.go

@@ -343,8 +343,10 @@ func GetAliasByCell(ctx context.Context, ts *Server, cell string) string {
 // Close will close all connections to underlying topo Server.
 // It will nil all member variables, so any further access will panic.
 func (ts *Server) Close() {
-	ts.globalCell.Close()
-	if ts.globalReadOnlyCell != ts.globalCell {
+	if ts.globalCell != nil {
+		ts.globalCell.Close()
+	}
+	if ts.globalReadOnlyCell != nil && ts.globalReadOnlyCell != ts.globalCell {
 		ts.globalReadOnlyCell.Close()
 	}
 	ts.globalCell = nil