Conditional PUTs require a lock primitive that excludes competing gateway
processes sharing a backend filesystem. A successful flock call does not prove
that property: some clustered filesystem configurations accept flock but scope
it to one node, silently leaving cross-gateway check-and-publish races open.
Add an object-lock mode that lets operators select flock or fcntl for
filesystems where that primitive is cluster-coherent, local for the existing
per-process behavior, or none to reject conditional writes with NotImplemented.
Keep the legacy disable flag as an alias for local.
Shared lock modes now verify the selected primitive on the root lock filesystem
during startup and fail closed if it cannot be used. Runtime lock failures no
longer silently downgrade to process-local exclusion. The startup check cannot
establish cross-node coherence, so that remains an explicit operator
requirement.
ScoutFS defaults to none since posix locks are not cluster consistent, but
allow setting local for single node deployments.
Fixes#2351
Fail closed on unexpected advisory-lock errors instead of silently reducing
cross-process exclusion to a local mutex. Make local publish-slot waits honor
request cancellation. Move version snapshots under the publish lock so
concurrent versioned PUTs preserve publication order. Add regression coverage
for canceled lock waiters.
Also add an option to disable flock files and only rely on in process locking.
Replace the hardcoded 0644 defaultFilePerm with a NewFilePerm option on
the posix and scoutfs backends, exposed as the --file-perms flag and
VGW_FILE_PERMS env var alongside the existing dir-perms option.
The mode passed to open() is masked by the process umask, so the
O_TMPFILE path now chmods explicitly to match the CreateTemp fallback
path and give new objects the configured mode regardless of umask.
Ben McClelland
Kyd CaoandBen McClelland