nats-io/nats-server · error

Error truncating WAL: %v

Error message

Error truncating WAL: %v

What it means

wal.Truncate(index) failed while the node was truncating its WAL to a given term/index (e.g. after a snapshot install or conflict resolution). The error is recorded via setWriteErrLocked, which typically disables the store since the WAL is now in an unknown state; pterm/pindex are intentionally not updated.

Source

Thrown at server/raft.go:4367

		}
		// Make sure to reset commit and applied if above
		if n.commit > n.pindex {
			n.commit = n.pindex
		}
		if n.processed > n.commit {
			n.processed = n.commit
		}
		if n.applied > n.processed {
			n.applied = n.processed
		}
		// Refresh bytes count after truncate.
		var state StreamState
		n.wal.FastState(&state)
		n.bytes = state.Bytes
	}()

	if err := n.wal.Truncate(index); err != nil {
		n.warn("Error truncating WAL: %v", err)
		n.setWriteErrLocked(err)
		return
	}
	// Set after we know we have truncated properly.
	n.pterm, n.pindex = term, index

	// Invalidate cached entries the WAL no longer has.
	if index == 0 {
		n.resetPendingEntries()
	} else {
		for k, ae := range n.pae {
			if k > index {
				n.paeBytes -= n.entryStoreSize(ae)
				delete(n.pae, k)
			}
		}
	}

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Check disk space, permissions, and filesystem errors on the WAL directory
2. Restart the node so the WAL recovery/replay logic re-establishes consistency
3. If the WAL is unrecoverable, reset the stream/raft state and re-sync from peers

When it happens

Trigger: Thrown at server/raft.go:4367 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/b310899dcdd2250c. Report an issue: GitHub.