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

Check disk space and the wrapped OS error from Flush

error while flushing to the snapshot file: %s

Error message

error while flushing to the snapshot file: %s

What it means

Done finalizes the snapshot: it flushes the buffered writer, then syncs and closes the file, returning the running hash. This error means the bufio flush to the snapshot file failed, so buffered data never reached the file and the snapshot is incomplete. Note the trailing space in the message string is part of the format.

Source

Thrown at common/ledger/snapshot/file.go:102

	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())
	}
	if err := c.file.Sync(); err != nil {
		return nil, err
	}
	if err := c.file.Close(); err != nil {
		return nil, errors.Wrapf(err, "error while closing the snapshot file: %s ", c.file.Name())
	}
	return c.hasher.Sum(nil), nil
}

// Close closes the underlying file, if not already done. A consumer can invoke this function if the consumer
// encountered some error and simply wants to abandon the snapshot file creation (typically, intended to be used in a defer statement)
func (c *FileWriter) Close() error {
	if c == nil {
		return nil
	}
	return errors.Wrapf(c.file.Close(), "error while closing the snapshot file: %s", c.file.Name())
}

View on GitHub (pinned to 2736b63f8f)

Solutions

Check disk space and the wrapped OS error from Flush
Re-run the snapshot export to produce a complete file
Ensure Done() is called exactly once and Close() is only used on the error path

Defensive patterns

Strategy: try-catch

Validate before calling

// before Done: ensure buffered data fits and disk has headroom
if free, _ := diskFree(snapshotDir); free < estimatedSize { return errors.New("not enough space to finalize snapshot") }

Try / catch

hash, err := w.Done()
if err != nil {
    w.Close() // best-effort cleanup
    return fmt.Errorf("snapshot finalization failed: %w", err)
}

Prevention

Call Done exactly once; use Close only for abandon paths
Reserve disk headroom larger than the largest expected buffer flush
Log the wrapped inner error from Flush for storage diagnosis

When it happens

Trigger: c.bufWriter.Flush() returns an error when Done is called (from exportUniqueTxIDs, ExportConfigHistory, or nested Done calls).

Common situations: Filesystem became full only at flush time (buffered writes deferred the failure), file handle invalidated, or an underlying disk I/O error surfacing at flush.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/eb231c76fea61e14. Report an issue: GitHub.