AlistGo/alist · error

invalid json

Error message

invalid json

What it means

unmarshalMetadata performs a cheap sanity pre-check before json.Unmarshal: the data must be at least 2 bytes and start with '{' and end with '}'. Failing this returns 'invalid json', meaning the metadata content is not a JSON object at all — truncated, empty, or garbage.

Source

Thrown at drivers/chunker/util.go:223

		Size:     &size,
		ChunkNum: &nChunks,
		MD5:      md5Value,
		SHA1:     sha1Value,
		XactID:   xactID,
	}
	data, err := json.Marshal(&meta)
	if err == nil && len(data) >= maxMetadataSizeWrite {
		return nil, errors.New("metadata can't be this big")
	}
	return data, err
}

func unmarshalMetadata(data []byte) (*chunkMetadata, error) {
	if len(data) > maxMetadataSizeWrite {
		return nil, errors.New("metadata is too large")
	}
	if data == nil || len(data) < 2 || data[0] != '{' || data[len(data)-1] != '}' {
		return nil, errors.New("invalid json")
	}
	var meta metadataJSON
	if err := json.Unmarshal(data, &meta); err != nil {
		return nil, err
	}
	if meta.Version == nil || meta.Size == nil || meta.ChunkNum == nil {
		return nil, errors.New("missing required field")
	}
	if *meta.Version < 1 {
		return nil, errors.New("wrong version")
	}
	if *meta.Size < 0 {
		return nil, errors.New("negative file size")
	}
	if *meta.ChunkNum < 1 || *meta.ChunkNum > maxSafeChunkNumber {
		return nil, errors.New("wrong number of chunks")
	}
	if meta.MD5 != "" {

View on GitHub (pinned to 843d9dc814)

Solutions

1. Inspect the actual metadata file content on the remote storage to see what it really contains
2. Delete the corrupted chunk set (metadata + chunk files) and re-upload the original file
3. If an error page was stored, fix the underlying storage driver/auth issue first, then re-upload

if len(data) < 2 || data[0] != '{' || data[len(data)-1] != '}' {
    return fmt.Errorf("metadata at %s is not a JSON object; got %q", path, truncate(data, 80))
}

meta, err := readMeta(ctx, p)
if err != nil && strings.Contains(err.Error(), "invalid json") {
    log.Printf("corrupt metadata for %s, first bytes: %q", p, head(data))
    // schedule re-upload of the file instead of retrying reads
}

When it happens

Trigger: A metadata companion file that is empty, a single byte, or whose first/last bytes are not braces — e.g. an HTML error page saved as the metadata file by a misbehaving remote, a truncated upload, or a plaintext marker written by another program. Raised whenever the chunker reads metadata for a chunked file.

Common situations: Remote storage returning an error page instead of file content; interrupted metadata writes; third-party tools creating similarly-named files that the chunker mistakes for metadata.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• metadata is too large
• negative file size
• metadata can't be this big
• missing required field
• wrong version

AI-assisted analysis of AlistGo/alist@843d9dc814 (2026-08-15). Data as JSON: /api/errors/2637eb6aadd60931. Report an issue: GitHub.