etcdutl: Fix snapshot restore memory alloc issue

When running the snapshot command, allow receiving an initial memory map
allocation for the database, avoiding future memory allocation issues.

Backports commit: be28833 / PR: #17277

Co-authored-by: Fatih USTA <fatihusta86@gmail.com>
Signed-off-by: Ivan Valdes <ivan@vald.es>

etcdctl/ctlv3/command/snapshot_command.go

@@ -42,6 +42,7 @@ var (
 	skipHashCheck       bool
 	markCompacted       bool
 	revisionBump        uint64
+	initialMmapSize     uint64
 )
 
 // NewSnapshotCommand returns the cobra command for "snapshot".
@@ -93,6 +94,7 @@ func NewSnapshotRestoreCommand() *cobra.Command {
 	cmd.Flags().BoolVar(&skipHashCheck, "skip-hash-check", false, "Ignore snapshot integrity hash value (required if copied from data directory)")
 	cmd.Flags().Uint64Var(&revisionBump, "bump-revision", 0, "How much to increase the latest revision after restore")
 	cmd.Flags().BoolVar(&markCompacted, "mark-compacted", false, "Mark the latest revision after restore as the point of scheduled compaction (required if --bump-revision > 0, disallowed otherwise)")
+	cmd.Flags().Uint64Var(&initialMmapSize, "initial-memory-map-size", initialMmapSize, "Initial memory map size of the database in bytes. It uses the default value if not defined or defined to 0")
 
 	return cmd
 }
@@ -131,7 +133,7 @@ func snapshotStatusCommandFunc(cmd *cobra.Command, args []string) {
 func snapshotRestoreCommandFunc(cmd *cobra.Command, args []string) {
 	fmt.Fprintf(os.Stderr, "Deprecated: Use `etcdutl snapshot restore` instead.\n\n")
 	etcdutl.SnapshotRestoreCommandFunc(restoreCluster, restoreClusterToken, restoreDataDir, restoreWalDir,
-		restorePeerURLs, restoreName, skipHashCheck, revisionBump, markCompacted, args)
+		restorePeerURLs, restoreName, skipHashCheck, initialMmapSize, revisionBump, markCompacted, args)
 }
 
 func initialClusterFromName(name string) string {

etcdutl/etcdutl/snapshot_command.go

@@ -21,6 +21,7 @@ import (
 	"go.etcd.io/etcd/etcdutl/v3/snapshot"
 	"go.etcd.io/etcd/pkg/v3/cobrautl"
 	"go.etcd.io/etcd/server/v3/datadir"
+	"go.etcd.io/etcd/server/v3/mvcc/backend"
 
 	"github.com/spf13/cobra"
 )
@@ -38,6 +39,7 @@ var (
 	restorePeerURLs     string
 	restoreName         string
 	skipHashCheck       bool
+	initialMmapSize     = backend.InitialMmapSize
 	markCompacted       bool
 	revisionBump        uint64
 )
@@ -93,6 +95,7 @@ func NewSnapshotRestoreCommand() *cobra.Command {
 	cmd.Flags().StringVar(&restorePeerURLs, "initial-advertise-peer-urls", defaultInitialAdvertisePeerURLs, "List of this member's peer URLs to advertise to the rest of the cluster")
 	cmd.Flags().StringVar(&restoreName, "name", defaultName, "Human-readable name for this member")
 	cmd.Flags().BoolVar(&skipHashCheck, "skip-hash-check", false, "Ignore snapshot integrity hash value (required if copied from data directory)")
+	cmd.Flags().Uint64Var(&initialMmapSize, "initial-memory-map-size", initialMmapSize, "Initial memory map size of the database in bytes. It uses the default value if not defined or defined to 0")
 	cmd.Flags().Uint64Var(&revisionBump, "bump-revision", 0, "How much to increase the latest revision after restore")
 	cmd.Flags().BoolVar(&markCompacted, "mark-compacted", false, "Mark the latest revision after restore as the point of scheduled compaction (required if --bump-revision > 0, disallowed otherwise)")
 
@@ -119,7 +122,7 @@ func SnapshotStatusCommandFunc(cmd *cobra.Command, args []string) {
 
 func snapshotRestoreCommandFunc(_ *cobra.Command, args []string) {
 	SnapshotRestoreCommandFunc(restoreCluster, restoreClusterToken, restoreDataDir, restoreWalDir,
-		restorePeerURLs, restoreName, skipHashCheck, revisionBump, markCompacted, args)
+		restorePeerURLs, restoreName, skipHashCheck, initialMmapSize, revisionBump, markCompacted, args)
 }
 
 func SnapshotRestoreCommandFunc(restoreCluster string,
@@ -129,6 +132,7 @@ func SnapshotRestoreCommandFunc(restoreCluster string,
 	restorePeerURLs string,
 	restoreName string,
 	skipHashCheck bool,
+	initialMmapSize uint64,
 	revisionBump uint64,
 	markCompacted bool,
 	args []string) {
@@ -164,6 +168,7 @@ func SnapshotRestoreCommandFunc(restoreCluster string,
 		InitialCluster:      restoreCluster,
 		InitialClusterToken: restoreClusterToken,
 		SkipHashCheck:       skipHashCheck,
+		InitialMmapSize:     initialMmapSize,
 		RevisionBump:        revisionBump,
 		MarkCompacted:       markCompacted,
 	}); err != nil {

etcdutl/snapshot/v3_snapshot.go

@@ -83,7 +83,8 @@ type v3Manager struct {
 	snapDir   string
 	cl        *membership.RaftCluster
 
-	skipHashCheck bool
+	skipHashCheck   bool
+	initialMmapSize uint64
 }
 
 // hasChecksum returns "true" if the file size "n"
@@ -197,6 +198,9 @@ type RestoreConfig struct {
 	// (required if copied from data directory).
 	SkipHashCheck bool
 
+	// InitialMmapSize is the database initial memory map size.
+	InitialMmapSize uint64
+
 	// RevisionBump is the amount to increase the latest revision after restore,
 	// to allow administrators to trick clients into thinking that revision never decreased.
 	// If 0, revision bumping is skipped.
@@ -256,13 +260,15 @@ func (s *v3Manager) Restore(cfg RestoreConfig) error {
 	s.walDir = walDir
 	s.snapDir = filepath.Join(dataDir, "member", "snap")
 	s.skipHashCheck = cfg.SkipHashCheck
+	s.initialMmapSize = cfg.InitialMmapSize
 
 	s.lg.Info(
 		"restoring snapshot",
 		zap.String("path", s.srcDbPath),
 		zap.String("wal-dir", s.walDir),
 		zap.String("data-dir", dataDir),
 		zap.String("snap-dir", s.snapDir),
+		zap.Uint64("initial-memory-map-size", s.initialMmapSize),
 	)
 
 	if err = s.saveDB(); err != nil {
@@ -290,6 +296,7 @@ func (s *v3Manager) Restore(cfg RestoreConfig) error {
 		zap.String("wal-dir", s.walDir),
 		zap.String("data-dir", dataDir),
 		zap.String("snap-dir", s.snapDir),
+		zap.Uint64("initial-memory-map-size", s.initialMmapSize),
 	)
 
 	return verify.VerifyIfEnabled(verify.Config{
@@ -310,7 +317,7 @@ func (s *v3Manager) saveDB() error {
 		return err
 	}
 
-	be := backend.NewDefaultBackend(s.outDbPath())
+	be := backend.NewDefaultBackend(s.outDbPath(), backend.WithMmapSize(s.initialMmapSize))
 	defer be.Close()
 
 	err = membership.TrimMembershipFromBackend(s.lg, be)
@@ -324,7 +331,7 @@ func (s *v3Manager) saveDB() error {
 // modifyLatestRevision can increase the latest revision by the given amount and sets the scheduled compaction
 // to that revision so that the server will consider this revision compacted.
 func (s *v3Manager) modifyLatestRevision(bumpAmount uint64) error {
-	be := backend.NewDefaultBackend(s.outDbPath())
+	be := backend.NewDefaultBackend(s.outDbPath(), backend.WithMmapSize(s.initialMmapSize))
 	defer func() {
 		be.ForceCommit()
 		be.Close()
@@ -467,7 +474,7 @@ func (s *v3Manager) saveWALAndSnap() (*raftpb.HardState, error) {
 	// add members again to persist them to the store we create.
 	st := v2store.New(etcdserver.StoreClusterPrefix, etcdserver.StoreKeysPrefix)
 	s.cl.SetStore(st)
-	be := backend.NewDefaultBackend(s.outDbPath())
+	be := backend.NewDefaultBackend(s.outDbPath(), backend.WithMmapSize(s.initialMmapSize))
 	defer be.Close()
 	s.cl.SetBackend(be)
 	for _, m := range s.cl.Members() {

server/mvcc/backend/backend.go

@@ -36,10 +36,10 @@ var (
 
 	defragLimit = 10000
 
-	// initialMmapSize is the initial size of the mmapped region. Setting this larger than
+	// InitialMmapSize is the initial size of the mmapped region. Setting this larger than
 	// the potential max db size can prevent writer from blocking reader.
 	// This only works for linux.
-	initialMmapSize = uint64(10 * 1024 * 1024 * 1024)
+	InitialMmapSize = uint64(10 * 1024 * 1024 * 1024)
 
 	// minSnapshotWarningTimeout is the minimum threshold to trigger a long running snapshot warning.
 	minSnapshotWarningTimeout = 30 * time.Second
@@ -157,7 +157,7 @@ func DefaultBackendConfig() BackendConfig {
 	return BackendConfig{
 		BatchInterval: defaultBatchInterval,
 		BatchLimit:    defaultBatchLimit,
-		MmapSize:      initialMmapSize,
+		MmapSize:      InitialMmapSize,
 	}
 }