Fix unreachable errors when taking a backup

changelog/21.0/21.0.0/release_notes.md

@@ -3,6 +3,8 @@
 
 ### Table of Contents
 
+- **[Known Issue](#known-issues)**
+  - **[Backup reports itself as successful despite failures](#backup-reports-as-successful)**
 - **[Major Changes](#major-changes)**
     - **[Deprecations and Deletions](#deprecations-and-deletions)**
         - [Deprecated VTTablet Flags](#vttablet-flags)
@@ -26,6 +28,14 @@
     - **[vtctldclient ChangeTabletTags](#vtctldclient-changetablettags)**
     - **[Support for specifying expected primary in reparents](#reparents-expectedprimary)**
 
+## <a id="known-issue"/>Known Issue</a>
+
+### <a id="backup-reports-as-successful"/>Backup reports itself as successful despite failures</a>
+
+In this release, we identified an issue where a backup may succeed even if a file fails to be backed up.
+Leading to a successful backup, even if some errors occurred.
+This only happen with the Builtin Backup Engine, and when all files have already been initiated in the backup process.
+For more details, please refer to the related GitHub Issue https://github.com/vitessio/vitess/issues/17063.
 
 ## <a id="major-changes"/>Major Changes</a>
 

changelog/21.0/21.0.0/summary.md

@@ -2,6 +2,8 @@
 
 ### Table of Contents
 
+- **[Known Issue](#known-issues)**
+    - **[Backup reports itself as successful despite failures](#backup-reports-as-successful)**
 - **[Major Changes](#major-changes)**
     - **[Deprecations and Deletions](#deprecations-and-deletions)**
         - [Deprecated VTTablet Flags](#vttablet-flags)
@@ -24,6 +26,14 @@
     - **[vtctldclient ChangeTabletTags](#vtctldclient-changetablettags)**
     - **[Support for specifying expected primary in reparents](#reparents-expectedprimary)**
 
+## <a id="known-issue"/>Known Issue</a>
+
+### <a id="backup-reports-as-successful"/>Backup reports itself as successful despite failures</a>
+
+In this release, we identified an issue where a backup may succeed even if a file fails to be backed up.
+Leading to a successful backup, even if some errors occurred.
+This only happen with the Builtin Backup Engine, and when all files have already been initiated in the backup process.
+For more details, please refer to the related GitHub Issue https://github.com/vitessio/vitess/issues/17063.
 
 ## <a id="major-changes"/>Major Changes</a>
 

go/vt/mysqlctl/backup_blackbox_race_test.go

@@ -0,0 +1,152 @@
+//go:build !race
+
+/*
+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 mysqlctl_test is the blackbox tests for package mysqlctl.
+package mysqlctl_test
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"vitess.io/vitess/go/mysql"
+	"vitess.io/vitess/go/mysql/fakesqldb"
+	"vitess.io/vitess/go/test/utils"
+	"vitess.io/vitess/go/vt/logutil"
+	"vitess.io/vitess/go/vt/mysqlctl"
+	"vitess.io/vitess/go/vt/mysqlctl/backupstats"
+	"vitess.io/vitess/go/vt/mysqlctl/filebackupstorage"
+	"vitess.io/vitess/go/vt/proto/topodata"
+	"vitess.io/vitess/go/vt/proto/vttime"
+	"vitess.io/vitess/go/vt/topo"
+	"vitess.io/vitess/go/vt/topo/memorytopo"
+)
+
+// This test triggers a certain code path that only happens when a backup file fails to be backed up,
+// only and only if, all the other backup files have either started or finished. When we reach
+// this scenario, files no longer try to acquire the semaphore and thus the backup cannot fail
+// because of context deadline when acquiring it. At this point, the only place where the backup
+// can fail, is if the return of be.backupFiles fails, and we record the error correctly.
+// This test specifically test this scenario and arose because of issue https://github.com/vitessio/vitess/issues/17063
+// The test does:
+//  1. Create the backup and data directory
+//  2. Create a keyspace and shard
+//  3. Already create the last backup file that would be created
+//  4. Remove all permissions on this file
+//  5. Execute the restore
+//  6. The restore must fail due to an error on file number 3 ("cannot add file: 3")
+//
+// This test is extracted into its own file that won't be run if we do 'go test -race' as this test
+// exposes an old race condition that will be fixed after https://github.com/vitessio/vitess/pull/17062
+// Link to the race condition issue: https://github.com/vitessio/vitess/issues/17065
+func TestExecuteBackupWithFailureOnLastFile(t *testing.T) {
+	ctx := utils.LeakCheckContext(t)
+
+	// Set up local backup directory
+	id := fmt.Sprintf("%d", time.Now().UnixNano())
+	backupRoot := fmt.Sprintf("testdata/builtinbackup_test_%s", id)
+	filebackupstorage.FileBackupStorageRoot = backupRoot
+	require.NoError(t, createBackupDir(backupRoot, "innodb", "log", "datadir"))
+	dataDir := path.Join(backupRoot, "datadir")
+	// Add some files under data directory to force backup to execute semaphore acquire inside
+	// backupFiles() method (https://github.com/vitessio/vitess/blob/main/go/vt/mysqlctl/builtinbackupengine.go#L483).
+	require.NoError(t, createBackupDir(dataDir, "test1"))
+	require.NoError(t, createBackupDir(dataDir, "test2"))
+	require.NoError(t, createBackupFiles(path.Join(dataDir, "test1"), 2, "ibd"))
+	require.NoError(t, createBackupFiles(path.Join(dataDir, "test2"), 2, "ibd"))
+	defer os.RemoveAll(backupRoot)
+
+	needIt, err := needInnoDBRedoLogSubdir()
+	require.NoError(t, err)
+	if needIt {
+		fpath := path.Join("log", mysql.DynamicRedoLogSubdir)
+		if err := createBackupDir(backupRoot, fpath); err != nil {
+			require.Failf(t, err.Error(), "failed to create directory: %s", fpath)
+		}
+	}
+
+	// Set up topo
+	keyspace, shard := "mykeyspace", "-"
+	ts := memorytopo.NewServer(ctx, "cell1")
+	defer ts.Close()
+
+	require.NoError(t, ts.CreateKeyspace(ctx, keyspace, &topodata.Keyspace{}))
+	require.NoError(t, ts.CreateShard(ctx, keyspace, shard))
+
+	tablet := topo.NewTablet(100, "cell1", "mykeyspace-00-80-0100")
+	tablet.Keyspace = keyspace
+	tablet.Shard = shard
+
+	require.NoError(t, ts.CreateTablet(ctx, tablet))
+
+	_, err = ts.UpdateShardFields(ctx, keyspace, shard, func(si *topo.ShardInfo) error {
+		si.PrimaryAlias = &topodata.TabletAlias{Uid: 100, Cell: "cell1"}
+
+		now := time.Now()
+		si.PrimaryTermStartTime = &vttime.Time{Seconds: int64(now.Second()), Nanoseconds: int32(now.Nanosecond())}
+
+		return nil
+	})
+
+	require.NoError(t, err)
+
+	be := &mysqlctl.BuiltinBackupEngine{}
+	bh := filebackupstorage.NewBackupHandle(nil, "", "", false)
+	// Spin up a fake daemon to be used in backups. It needs to be allowed to receive:
+	// "STOP REPLICA", "START REPLICA", in that order.
+	fakedb := fakesqldb.New(t)
+	defer fakedb.Close()
+	mysqld := mysqlctl.NewFakeMysqlDaemon(fakedb)
+	defer mysqld.Close()
+	mysqld.ExpectedExecuteSuperQueryList = []string{"STOP REPLICA", "START REPLICA"}
+
+	// With this setup, 4 backup files will be created (0, 1, 2, 3). For the last file (3), we create
+	// it in advance and remove all permission on the file so that the backup be.ExecuteBackup will not
+	// be able to override the file and thus will fail. Triggering the error mechanism after calling be.backupFile.
+	lastBackupFile := path.Join(backupRoot, "3")
+	f, err := os.Create(lastBackupFile)
+	require.NoError(t, err)
+	_, err = f.Write(make([]byte, 1024))
+	require.NoError(t, err)
+	require.NoError(t, f.Chmod(0444))
+	require.NoError(t, f.Close())
+
+	backupResult, err := be.ExecuteBackup(ctx, mysqlctl.BackupParams{
+		Logger: logutil.NewConsoleLogger(),
+		Mysqld: mysqld,
+		Cnf: &mysqlctl.Mycnf{
+			InnodbDataHomeDir:     path.Join(backupRoot, "innodb"),
+			InnodbLogGroupHomeDir: path.Join(backupRoot, "log"),
+			DataDir:               path.Join(backupRoot, "datadir"),
+		},
+		Stats:                backupstats.NewFakeStats(),
+		Concurrency:          4,
+		HookExtraEnv:         map[string]string{},
+		TopoServer:           ts,
+		Keyspace:             keyspace,
+		Shard:                shard,
+		MysqlShutdownTimeout: mysqlShutdownTimeout,
+	}, bh)
+
+	require.ErrorContains(t, err, "cannot add file: 3")
+	require.Equal(t, mysqlctl.BackupUnusable, backupResult)
+}

go/vt/mysqlctl/builtinbackupengine.go

@@ -643,9 +643,8 @@ func (be *BuiltinBackupEngine) backupFiles(
 
 			// Backup the individual file.
 			name := fmt.Sprintf("%v", i)
-			err := be.backupFile(ctxCancel, params, bh, fe, name)
-			if err != nil {
-				bh.RecordError(acqErr)
+			if err := be.backupFile(ctxCancel, params, bh, fe, name); err != nil {
+				bh.RecordError(err)
 				cancel()
 			}
 		}(i)