blob save fsync feature flag (#13652)

Co-authored-by: Kasey Kirkham <kasey@users.noreply.github.com>

beacon-chain/db/filesystem/blob.go

@@ -24,6 +24,7 @@ var (
 	errIndexOutOfBounds    = errors.New("blob index in file name >= MaxBlobsPerBlock")
 	errEmptyBlobWritten    = errors.New("zero bytes written to disk when saving blob sidecar")
 	errSidecarEmptySSZData = errors.New("sidecar marshalled to an empty ssz byte slice")
+	errNoBasePath          = errors.New("BlobStorage base path not specified in init")
 )
 
 const (
@@ -36,14 +37,26 @@ const (
 // BlobStorageOption is a functional option for configuring a BlobStorage.
 type BlobStorageOption func(*BlobStorage) error
 
+// WithBasePath is a required option that sets the base path of blob storage.
+func WithBasePath(base string) BlobStorageOption {
+	return func(b *BlobStorage) error {
+		b.base = base
+		return nil
+	}
+}
+
 // WithBlobRetentionEpochs is an option that changes the number of epochs blobs will be persisted.
 func WithBlobRetentionEpochs(e primitives.Epoch) BlobStorageOption {
 	return func(b *BlobStorage) error {
-		pruner, err := newBlobPruner(b.fs, e)
-		if err != nil {
-			return err
-		}
-		b.pruner = pruner
+		b.retentionEpochs = e
+		return nil
+	}
+}
+
+// WithSaveFsync is an option that causes Save to call fsync before renaming part files for improved durability.
+func WithSaveFsync(fsync bool) BlobStorageOption {
+	return func(b *BlobStorage) error {
+		b.fsync = fsync
 		return nil
 	}
 }
@@ -51,30 +64,36 @@ func WithBlobRetentionEpochs(e primitives.Epoch) BlobStorageOption {
 // NewBlobStorage creates a new instance of the BlobStorage object. Note that the implementation of BlobStorage may
 // attempt to hold a file lock to guarantee exclusive control of the blob storage directory, so this should only be
 // initialized once per beacon node.
-func NewBlobStorage(base string, opts ...BlobStorageOption) (*BlobStorage, error) {
-	base = path.Clean(base)
-	if err := file.MkdirAll(base); err != nil {
-		return nil, fmt.Errorf("failed to create blob storage at %s: %w", base, err)
-	}
-	fs := afero.NewBasePathFs(afero.NewOsFs(), base)
-	b := &BlobStorage{
-		fs: fs,
-	}
+func NewBlobStorage(opts ...BlobStorageOption) (*BlobStorage, error) {
+	b := &BlobStorage{}
 	for _, o := range opts {
 		if err := o(b); err != nil {
-			return nil, fmt.Errorf("failed to create blob storage at %s: %w", base, err)
+			return nil, errors.Wrap(err, "failed to create blob storage")
 		}
 	}
-	if b.pruner == nil {
-		log.Warn("Initializing blob filesystem storage with pruning disabled")
+	if b.base == "" {
+		return nil, errNoBasePath
 	}
+	b.base = path.Clean(b.base)
+	if err := file.MkdirAll(b.base); err != nil {
+		return nil, errors.Wrapf(err, "failed to create blob storage at %s", b.base)
+	}
+	b.fs = afero.NewBasePathFs(afero.NewOsFs(), b.base)
+	pruner, err := newBlobPruner(b.fs, b.retentionEpochs)
+	if err != nil {
+		return nil, err
+	}
+	b.pruner = pruner
 	return b, nil
 }
 
 // BlobStorage is the concrete implementation of the filesystem backend for saving and retrieving BlobSidecars.
 type BlobStorage struct {
-	fs     afero.Fs
-	pruner *blobPruner
+	base            string
+	retentionEpochs primitives.Epoch
+	fsync           bool
+	fs              afero.Fs
+	pruner          *blobPruner
 }
 
 // WarmCache runs the prune routine with an expiration of slot of 0, so nothing will be pruned, but the pruner's cache
@@ -151,8 +170,13 @@ func (bs *BlobStorage) Save(sidecar blocks.VerifiedROBlob) error {
 		}
 		return errors.Wrap(err, "failed to write to partial file")
 	}
-	err = partialFile.Close()
-	if err != nil {
+	if bs.fsync {
+		if err := partialFile.Sync(); err != nil {
+			return err
+		}
+	}
+
+	if err := partialFile.Close(); err != nil {
 		return err
 	}
 

beacon-chain/db/filesystem/blob_test.go

@@ -108,7 +108,7 @@ func TestBlobStorage_SaveBlobData(t *testing.T) {
 		// to be empty. This test ensures that several routines can safely save the same blob at the
 		// same time. This isn't ideal behavior from the caller, but should be handled safely anyway.
 		// See https://github.com/prysmaticlabs/prysm/pull/13648
-		b, err := NewBlobStorage(t.TempDir())
+		b, err := NewBlobStorage(WithBasePath(t.TempDir()))
 		require.NoError(t, err)
 		blob := testSidecars[0]
 
@@ -268,6 +268,8 @@ func BenchmarkPruning(b *testing.B) {
 }
 
 func TestNewBlobStorage(t *testing.T) {
-	_, err := NewBlobStorage(path.Join(t.TempDir(), "good"))
+	_, err := NewBlobStorage()
+	require.ErrorIs(t, err, errNoBasePath)
+	_, err = NewBlobStorage(WithBasePath(path.Join(t.TempDir(), "good")))
 	require.NoError(t, err)
 }

beacon-chain/node/node.go

@@ -118,6 +118,7 @@ type BeaconNode struct {
 	BackfillOpts            []backfill.ServiceOption
 	initialSyncComplete     chan struct{}
 	BlobStorage             *filesystem.BlobStorage
+	BlobStorageOptions      []filesystem.BlobStorageOption
 	blobRetentionEpochs     primitives.Epoch
 	verifyInitWaiter        *verification.InitializerWaiter
 	syncChecker             *initialsync.SyncChecker
@@ -209,6 +210,16 @@ func New(cliCtx *cli.Context, cancel context.CancelFunc, opts ...Option) (*Beaco
 		return nil, err
 	}
 
+	// Allow tests to set it as an opt.
+	if beacon.BlobStorage == nil {
+		beacon.BlobStorageOptions = append(beacon.BlobStorageOptions, filesystem.WithSaveFsync(features.Get().BlobSaveFsync))
+		blobs, err := filesystem.NewBlobStorage(beacon.BlobStorageOptions...)
+		if err != nil {
+			return nil, err
+		}
+		beacon.BlobStorage = blobs
+	}
+
 	log.Debugln("Starting DB")
 	if err := beacon.startDB(cliCtx, depositAddress); err != nil {
 		return nil, err

beacon-chain/node/options.go

@@ -43,6 +43,15 @@ func WithBlobStorage(bs *filesystem.BlobStorage) Option {
 	}
 }
 
+// WithBlobStorageOptions appends 1 or more filesystem.BlobStorageOption on the beacon node,
+// to be used when initializing blob storage.
+func WithBlobStorageOptions(opt ...filesystem.BlobStorageOption) Option {
+	return func(bn *BeaconNode) error {
+		bn.BlobStorageOptions = append(bn.BlobStorageOptions, opt...)
+		return nil
+	}
+}
+
 // WithBlobRetentionEpochs sets the blobRetentionEpochs value, used in kv store initialization.
 func WithBlobRetentionEpochs(e primitives.Epoch) Option {
 	return func(bn *BeaconNode) error {

cmd/beacon-chain/storage/options.go

@@ -35,11 +35,10 @@ func BeaconNodeOptions(c *cli.Context) ([]node.Option, error) {
 	if err != nil {
 		return nil, err
 	}
-	bs, err := filesystem.NewBlobStorage(blobStoragePath(c), filesystem.WithBlobRetentionEpochs(e))
-	if err != nil {
-		return nil, err
-	}
-	return []node.Option{node.WithBlobStorage(bs), node.WithBlobRetentionEpochs(e)}, nil
+	opts := []node.Option{node.WithBlobStorageOptions(
+		filesystem.WithBlobRetentionEpochs(e), filesystem.WithBasePath(blobStoragePath(c)),
+	)}
+	return opts, nil
 }
 
 func blobStoragePath(c *cli.Context) string {

config/features/config.go

@@ -69,7 +69,8 @@ type Flags struct {
 	EnableEIP4881                bool // EnableEIP4881 specifies whether to use the deposit tree from EIP4881
 
 	PrepareAllPayloads bool // PrepareAllPayloads informs the engine to prepare a block on every slot.
-
+	// BlobSaveFsync requires blob saving to block on fsync to ensure blobs are durably persisted before passing DA.
+	BlobSaveFsync bool
 	// KeystoreImportDebounceInterval specifies the time duration the validator waits to reload new keys if they have
 	// changed on disk. This feature is for advanced use cases only.
 	KeystoreImportDebounceInterval time.Duration
@@ -245,6 +246,11 @@ func ConfigureBeaconChain(ctx *cli.Context) error {
 		logEnabled(EnableLightClient)
 		cfg.EnableLightClient = true
 	}
+	if ctx.IsSet(BlobSaveFsync.Name) {
+		logEnabled(BlobSaveFsync)
+		cfg.BlobSaveFsync = true
+	}
+
 	cfg.AggregateIntervals = [3]time.Duration{aggregateFirstInterval.Value, aggregateSecondInterval.Value, aggregateThirdInterval.Value}
 	Init(cfg)
 	return nil

config/features/flags.go

@@ -149,12 +149,16 @@ var (
 		Name:  "disable-resource-manager",
 		Usage: "Disables running the libp2p resource manager.",
 	}
-
 	// DisableRegistrationCache a flag for disabling the validator registration cache and use db instead.
 	DisableRegistrationCache = &cli.BoolFlag{
 		Name:  "disable-registration-cache",
 		Usage: "Temporary flag for disabling the validator registration cache instead of using the DB. Note: registrations do not clear on restart while using the DB.",
 	}
+	// BlobSaveFsync enforces durable filesystem writes for use cases where blob availability is critical.
+	BlobSaveFsync = &cli.BoolFlag{
+		Name:  "blob-save-fsync",
+		Usage: "Forces new blob files to be fysnc'd before continuing, ensuring durable blob writes.",
+	}
 )
 
 // devModeFlags holds list of flags that are set when development mode is on.
@@ -209,6 +213,7 @@ var BeaconChainFlags = append(deprecatedBeaconFlags, append(deprecatedFlags, []c
 	disableResourceManager,
 	DisableRegistrationCache,
 	EnableLightClient,
+	BlobSaveFsync,
 }...)...)
 
 // E2EBeaconChainFlags contains a list of the beacon chain feature flags to be tested in E2E.