nats-io/nats-server · error

Snapshot with last index 0 is invalid, cleaning up

Error message

Snapshot with last index 0 is invalid, cleaning up

What it means

The loaded snapshot has lastIndex == 0, produced by a bug in v2.9.12 that allowed empty snapshots. Such a snapshot carries no usable state, so it is cleaned up and the node proceeds without it (WAL/leader catchup re-establishes state).

Source

Thrown at server/raft.go:2062

	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
	}

	var le = binary.LittleEndian
	lps := le.Uint32(buf[16:])
	snap := &snapshot{
		lastTerm:  le.Uint64(buf[0:]),
		lastIndex: le.Uint64(buf[8:]),
		peerstate: buf[20 : 20+lps],
		data:      buf[20+lps : hoff],
	}

	// We had a bug in 2.9.12 that would allow snapshots on last index of 0.
	// Detect that and continue anyway, nothing else we can do about it.
	if snap.lastIndex == 0 {
		n.warn("Snapshot with last index 0 is invalid, cleaning up")
		os.Remove(n.snapfile)
		n.snapfile = _EMPTY_
		return nil, errNoSnapAvailable
	}

	return snap, nil
}

// Leader returns if we are the leader for our group.
// We use an atomic here now vs acquiring the read lock.
func (n *raft) Leader() bool {
	if n == nil {
		return false
	}
	return n.leaderState.Load()
}

// LeaderSince returns how long we have been leader for,

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Upgrade from 2.9.12 to a fixed release
2. No data recovery needed: index-0 snapshots hold nothing of value
3. The node re-snapshots normally on next snapshot cycle

When it happens

Trigger: Thrown at server/raft.go:2062 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/aa6b4dbd38b4a043. Report an issue: GitHub.