* feat(filer): add lazy directory listing for remote mounts
Directory listings on remote mounts previously only queried the local
filer store. With lazy mounts the listing was empty; with eager mounts
it went stale over time.
Add on-demand directory listing that fetches from remote and caches
results with a 5-minute TTL:
- Add `ListDirectory` to `RemoteStorageClient` interface (delimiter-based,
single-level listing, separate from recursive `Traverse`)
- Implement in S3, GCS, and Azure backends using each platform's
hierarchical listing API
- Add `maybeLazyListFromRemote` to filer: before each directory listing,
check if the directory is under a remote mount with an expired cache,
fetch from remote, persist entries to the local store, then let existing
listing logic run on the populated store
- Use singleflight to deduplicate concurrent requests for the same directory
- Skip local-only entries (no RemoteEntry) to avoid overwriting unsynced uploads
- Errors are logged and swallowed (availability over consistency)
* refactor: extract xattr key to constant xattrRemoteListingSyncedAt
* feat: make listing cache TTL configurable per mount via listing_cache_ttl_seconds
Add listing_cache_ttl_seconds field to RemoteStorageLocation protobuf.
When 0 (default), lazy directory listing is disabled for that mount.
When >0, enables on-demand directory listing with the specified TTL.
Expose as -listingCacheTTL flag on remote.mount command.
* refactor: address review feedback for lazy directory listing
- Add context.Context to ListDirectory interface and all implementations
- Capture startTime before remote call for accurate TTL tracking
- Simplify S3 ListDirectory using ListObjectsV2PagesWithContext
- Make maybeLazyListFromRemote return void (errors always swallowed)
- Remove redundant trailing-slash path manipulation in caller
- Update tests to match new signatures
* When an existing entry has Remote != nil, we should merge remote metadata into it rather than replacing it.
* fix(gcs): wrap ListDirectory iterator error with context
The raw iterator error was returned without bucket/path context,
making it harder to debug. Wrap it consistently with the S3 pattern.
* fix(s3): guard against nil pointer dereference in Traverse and ListDirectory
Some S3-compatible backends may return nil for LastModified, Size, or
ETag fields. Check for nil before dereferencing to prevent panics.
* fix(filer): remove blanket 2-minute timeout from lazy listing context
Individual SDK operations (S3, GCS, Azure) already have per-request
timeouts and retry policies. The blanket timeout could cut off large
directory listings mid-operation even though individual pages were
succeeding.
* fix(filer): preserve trace context in lazy listing with WithoutCancel
Use context.WithoutCancel(ctx) instead of context.Background() so
trace/span values from the incoming request are retained for
distributed tracing, while still decoupling cancellation.
* fix(filer): use Store.FindEntry for internal lookups, add Uid/Gid to files, fix updateDirectoryListingSyncedAt
- Use f.Store.FindEntry instead of f.FindEntry for staleness check and
child lookups to avoid unnecessary lazy-fetch overhead
- Set OS_UID/OS_GID on new file entries for consistency with directories
- In updateDirectoryListingSyncedAt, use Store.UpdateEntry for existing
directories instead of CreateEntry to avoid deleteChunksIfNotNew and
NotifyUpdateEvent side effects
* fix(filer): distinguish not-found from store errors in lazy listing
Previously, any error from Store.FindEntry was treated as "not found,"
which could cause entry recreation/overwrite on transient DB failures.
Now check for filer_pb.ErrNotFound explicitly and skip entries or
bail out on real store errors.
* refactor(filer): use errors.Is for ErrNotFound comparisons
