weaviate/weaviate · error

unexpected error, node size mismatch

Error message

unexpected error, node size mismatch

What it means

Before appending a replace-type node to the write-ahead log, the commit logger verifies that the serialized node buffer length equals the value range written into the key index (ki.ValueEnd-ki.ValueStart). A mismatch means the serializer wrote a different number of bytes than it recorded in the index, i.e. an internal serialization invariant was violated. The entry is rejected instead of writing a WAL record that later parsing could not decode.

Source

Thrown at adapters/repos/db/lsmkv/commitlogger.go:349

	cl.n.Add(int64(1 + 1 + 4 + len(nodeBytes) + checksumSize))

	return nil
}

func (cl *commitLogger) put(node segmentReplaceNode) error {
	if cl.paused {
		return nil
	}

	cl.bufNode.Reset()

	ki, err := node.KeyIndexAndWriteTo(cl.bufNode)
	if err != nil {
		return err
	}
	if len(cl.bufNode.Bytes()) != ki.ValueEnd-ki.ValueStart {
		return fmt.Errorf("unexpected error, node size mismatch")
	}

	return cl.writeEntry(CommitTypeReplace, cl.bufNode.Bytes())
}

func (cl *commitLogger) append(node segmentCollectionNode) error {
	if cl.paused {
		return nil
	}

	cl.bufNode.Reset()

	ki, err := node.KeyIndexAndWriteTo(cl.bufNode)
	if err != nil {
		return err
	}
	if len(cl.bufNode.Bytes()) != ki.ValueEnd-ki.ValueStart {
		return fmt.Errorf("unexpected error, node size mismatch")

View on GitHub (pinned to 75aa4b6d11)

Solutions

1. Retry the operation; if transient it indicates a race — check for concurrent writes to the same bucket
2. Upgrade to the latest Weaviate version, as this guards against serializer bugs fixed upstream
3. Capture the WAL file and report a bug with the object/key involved
4. Verify the bucket's WAL files are not corrupted (truncated WAL can desync buffered state)

err := bucket.Put(ctx, []byte(key), value)
if err != nil {
    if strings.Contains(err.Error(), "node size mismatch") {
        // serialization invariant violated: do not spin; escalate
        return fmt.Errorf("wal serializer invariant violated, please report: %w", err)
    }
    return err
}

When it happens

Trigger: Calling commitlogger.Put with a segmentReplaceNode whose KeyIndexAndWriteTo serializes bytes inconsistent with its reported value range — a bug in the node serializer or a bufNode reused with stale contents.

Common situations: Encountered during development of lsmkv changes or on corrupted in-memory node state; practically never caused by user configuration.

Related errors

• primary index size mismatch: expected %d bytes, wrote %d
• write secondary index %d: %w
• flushing WAL %q: %w
• unsupported commit version %d
• unsupported commit version %d

AI-assisted analysis of weaviate/weaviate@75aa4b6d11 (2026-09-04). Data as JSON: /api/errors/980ae7d5a05a6981. Report an issue: GitHub.