mysqlctl: open backup files with fadvise(2) and FADV_SEQUENTIAL (#16441)

Signed-off-by: Matt Robenolt <[email protected]>

go/vt/mysqlctl/builtinbackupengine.go

@@ -92,8 +92,7 @@ var (
 // it implements the BackupEngine interface and contains all the logic
 // required to implement a backup/restore by copying files from and to
 // the correct location / storage bucket
-type BuiltinBackupEngine struct {
-}
+type BuiltinBackupEngine struct{}
 
 // builtinBackupManifest represents the backup. It lists all the files, the
 // Position that the backup was taken at, the compression engine used, etc.
@@ -186,15 +185,15 @@ func (fe *FileEntry) fullPath(cnf *Mycnf) (string, error) {
 	return path.Join(fe.ParentPath, root, fe.Name), nil
 }
 
-// open attempts t oopen the file
+// open attempts to open the file
 func (fe *FileEntry) open(cnf *Mycnf, readOnly bool) (*os.File, error) {
 	name, err := fe.fullPath(cnf)
 	if err != nil {
 		return nil, vterrors.Wrapf(err, "cannot evaluate full name for %v", fe.Name)
 	}
 	var fd *os.File
 	if readOnly {
-		if fd, err = os.Open(name); err != nil {
+		if fd, err = openForSequential(name); err != nil {
 			return nil, vterrors.Wrapf(err, "cannot open source file %v", name)
 		}
 	} else {
@@ -393,7 +392,6 @@ func (be *BuiltinBackupEngine) executeIncrementalBackup(ctx context.Context, par
 // executeFullBackup returns a BackupResult that indicates the usability of the backup,
 // and an overall error.
 func (be *BuiltinBackupEngine) executeFullBackup(ctx context.Context, params BackupParams, bh backupstorage.BackupHandle) (BackupResult, error) {
-
 	if params.IncrementalFromPos != "" {
 		return be.executeIncrementalBackup(ctx, params, bh)
 	}
@@ -968,7 +966,6 @@ func (be *BuiltinBackupEngine) executeRestoreIncrementalBackup(ctx context.Conte
 // we return the position from which replication should start
 // otherwise an error is returned
 func (be *BuiltinBackupEngine) ExecuteRestore(ctx context.Context, params RestoreParams, bh backupstorage.BackupHandle) (*BackupManifest, error) {
-
 	var bm builtinBackupManifest
 	if err := getBackupManifestInto(ctx, bh, &bm); err != nil {
 		return nil, err
@@ -1108,7 +1105,7 @@ func (be *BuiltinBackupEngine) restoreFile(ctx context.Context, params RestorePa
 	// Create the uncompresser if needed.
 	if !bm.SkipCompress {
 		var decompressor io.ReadCloser
-		var deCompressionEngine = bm.CompressionEngine
+		deCompressionEngine := bm.CompressionEngine
 
 		if deCompressionEngine == "" {
 			// for backward compatibility

go/vt/mysqlctl/builtinbackupengine_linux.go

@@ -0,0 +1,44 @@
+/*
+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
+li*/
+
+package mysqlctl
+
+import (
+	"os"
+
+	"golang.org/x/sys/unix"
+)
+
+// openForSequential opens a file and hints to the kernel that this file
+// is intended to be read sequentially, setting the FADV_SEQUENTIAL flag.
+// See: https://linux.die.net/man/2/fadvise
+func openForSequential(name string) (*os.File, error) {
+	f, err := os.Open(name)
+	if err != nil {
+		return nil, err
+	}
+	// XXX: beyond this path, if we error, we need to close
+	// our File since we're not returning it anymore.
+	fstat, err := f.Stat()
+	if err != nil {
+		f.Close()
+		return nil, err
+	}
+	if err := unix.Fadvise(int(f.Fd()), 0, fstat.Size(), unix.FADV_SEQUENTIAL); err != nil {
+		f.Close()
+		return nil, err
+	}
+	return f, nil
+}

go/vt/mysqlctl/builtinbackupengine_stub.go

@@ -0,0 +1,24 @@
+//go:build !linux
+
+/*
+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
+li*/
+
+package mysqlctl
+
+import "os"
+
+func openForSequential(name string) (*os.File, error) {
+	return os.Open(name)
+}