nats-io/nats-server · error

Error reading snapshot: %v

Error message

Error reading snapshot: %v

What it means

A warning logged by raft.loadLastSnapshot() when reading the node's snapshot file fails (os.ReadFile error such as missing, permission-denied, or I/O error). The function returns the error, so the node cannot restore from the last snapshot and must rely on WAL replay or peer catch-up.

Source

Thrown at server/raft.go:2031

	if snap.lastIndex != n.papplied {
		return 0, nil, errors.New("snapshot index mismatch")
	}
	return snap.lastIndex, snap.data, nil
}

// loadLastSnapshot will load and return our last snapshot.
// Lock should be held.
func (n *raft) loadLastSnapshot() (*snapshot, error) {
	if n.snapfile == _EMPTY_ {
		return nil, errNoSnapAvailable
	}

	n.dios.acquire()
	buf, err := os.ReadFile(n.snapfile)
	n.dios.release()

	if err != nil {
		n.warn("Error reading snapshot: %v", err)
		return nil, err
	}
	if len(buf) < minSnapshotLen {
		n.warn("Snapshot corrupt, too short")
		return nil, errSnapshotCorrupt
	}

	// Check to make sure hash is consistent.
	hoff := len(buf) - 8
	lchk := buf[hoff:]
	n.hh.Reset()
	n.hh.Write(buf[:hoff])
	var hb [highwayhash.Size64]byte
	if !bytes.Equal(lchk[:], n.hh.Sum(hb[:0])) {
		n.warn("Snapshot corrupt, checksums did not match")
		return nil, errSnapshotCorrupt
	}

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Check the snapshot file's existence and permissions at the path derived from the wrapped error
2. Verify disk health for the raft storage directory
3. If the snapshot is unrecoverable, resync the node from an intact peer

When it happens

Trigger: Thrown at server/raft.go:2031 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of nats-io/nats-server@3a66a489d2 (2026-09-02). Data as JSON: /api/errors/1e8df19fe41ee233. Report an issue: GitHub.