What causes "error while writing data to the snapshot file: %s" in hyperledger/fabric?

Check free disk space on the snapshot output path

error while writing data to the snapshot file: %s

Error message

error while writing data to the snapshot file: %s

What it means

EncodeBytes writes a uvarint length prefix followed by the raw bytes to the snapshot file's multiWriter (file + buffered hash writer). This error means the Write call on the data bytes failed after the length prefix may already have been written, so the snapshot stream is potentially truncated. The wrapped OS error gives the concrete cause (disk full, bad fd, etc.).

Source

Thrown at common/ledger/snapshot/file.go:85

// EncodeProtoMessage encodes and appends a proto message to the data stream
func (c *FileWriter) EncodeProtoMessage(m proto.Message) error {
	if m == nil || !m.ProtoReflect().IsValid() {
		return errors.Errorf("error marshalling proto message to write to the snapshot file: %s: proto: Marshal called with nil", c.file.Name())
	}
	b, err := proto.Marshal(m)
	if err != nil {
		return errors.Wrapf(err, "error marshalling proto message to write to the snapshot file: %s", c.file.Name())
	}
	return c.EncodeBytes(b)
}

// EncodeBytes encodes and appends bytes to the data stream
func (c *FileWriter) EncodeBytes(b []byte) error {
	if err := c.EncodeUVarint(uint64(len(b))); err != nil {
		return err
	}
	if _, err := c.multiWriter.Write(b); err != nil {
		return errors.Wrapf(err, "error while writing data to the snapshot file: %s", c.file.Name())
	}
	return nil
}

// EncodeUVarint encodes and appends a number to the data stream
func (c *FileWriter) EncodeUVarint(u uint64) error {
	n := binary.PutUvarint(c.varintReusableBuf, u)
	if _, err := c.multiWriter.Write(c.varintReusableBuf[:n]); err != nil {
		return errors.Wrapf(err, "error while writing data to the snapshot file: %s", c.file.Name())
	}
	return nil
}

// Done closes the snapshot file and returns the final hash of the data stream
func (c *FileWriter) Done() ([]byte, error) {
	if err := c.bufWriter.Flush(); err != nil {
		return nil, errors.Wrapf(err, "error while flushing to the snapshot file: %s ", c.file.Name())
	}

View on GitHub (pinned to 2736b63f8f)

Solutions

Check free disk space on the snapshot output path
Inspect the wrapped inner error for the OS-level cause
Retry the snapshot export after resolving the storage issue

Defensive patterns

Strategy: try-catch

Validate before calling

if st, err := os.Stat(outDir); err != nil || !st.IsDir() { return errors.New("invalid snapshot dir") }
if us := getFreeSpace(outDir); us < minRequired { return errors.New("insufficient disk space") }

Try / catch

if err := w.EncodeBytes(data); err != nil {
    var pe *fs.PathError
    if errors.As(err, &pe) { log.Errorf("snapshot write failed: %v", pe) }
    w.Close() // abandon snapshot
    return err
}

Prevention

Check free disk space before starting an export
Write snapshots to local, not network, storage
Always defer Close() on error paths to avoid partial files

When it happens

Trigger: c.multiWriter.Write(b) returns an error while encoding bytes appended via EncodeString, EncodeProtoMessage, or ExportConfigHistory.

Common situations: Disk quota exceeded or filesystem full on the snapshot output directory; snapshot file deleted/rotated mid-write; running out of file descriptors or hitting an I/O error on a network-backed volume.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/8d89f309d9e35798. Report an issue: GitHub.