Attributes

Key-value metadata that can be set for any inode, versioned separately from file content.

Understanding attributes

Attributes record arbitrary key/value metadata on a file or folder. They are applied to the underlying inode (so a rename or a move does not impact attributes).

{
  "inode_id": "ino_42",
  "path": "/reports/q3.csv",
  "inode_kind": "file",
  "revision_no": 3,
  // … content_ref, size_bytes, head_seq and other hidden fields
  "attributes_revision_no": 7,
  "attributes": {
    "owner": "finance",
    "status": "final"
  }
}

Setting attributes

Attributes can be set using the commit operation update_attributes (see Transactions).

Reading attributes

statincludes attributes by default, andlistomits them by default (because a page can contain 1,000 entries). Useinclude_attributes=true` if needed.

See Stat a path and List path entries.

CLI

Attributes can be set and removed using the annotate command in the CLI.

loonfs annotate /reports/q3.csv --set owner=finance --set status=final
loonfs annotate /reports/q3.csv --remove status

Attribute revisions vs. content revisions

An inode records a revision history for attributes incremented by attributes_revision_no (not to be confused with the revision_no for content). Writing attributes does not produce a file revision, and updating content does not affect attribute revisions.

Limits

Attribute keys and values are strings, and limits are measured in units of UTF-8 bytes.

Constraint	Maximum
Attribute key length	128 UTF-8 bytes
Attribute value length	4,096 UTF-8 bytes
Total entries on one inode	100
Total size of attributes on one inode	65,536 UTF-8 bytes