* filer: add filer.options.disable_remote_storage_deletion for cache-only deletes
Deleting a filer entry under a remote.mount path also deletes the backing
object from the remote store (maybeDeleteFromRemote). Deployments that use a
remote mount as a read-through cache in front of an authoritative,
externally-managed object store cannot allow this: the filer typically holds
read-only credentials, so the remote delete fails and the entire delete
errors out; and even where it would succeed, it destroys data the filer does
not own.
Add filer.options.disable_remote_storage_deletion (default false, so existing
behaviour is unchanged). When enabled, maybeDeleteFromRemote is skipped for
both single-entry and recursive folder deletes: local metadata and cached
chunks are still removed, but the remote object is left intact.
* filer: assert local removal in cache-only recursive delete test
The recursive cache-only delete test only checked that no remote delete
happened; it did not verify the local child and directory entries were
removed. Add FindEntry assertions so a regression that skips local
recursive deletion is caught.
* filer: reload the remote mount mapping when /etc/remote changes
The mapping was only read at startup, so remote.unmount left the mount live
in the filer: the purge that follows the mapping delete then went to the
remote store and wiped every object under the mount.
Rebuild the rules trie and the conf map from scratch on each load, since
ptrie cannot drop a key, and swap them under a lock.
* filer: drop the filer-wide remote deletion switch
With the mapping reloaded on unmount, the purge no longer reaches the remote
store, so there is nothing left for the switch to protect against.
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Co-authored-by: Chris Lu <chris.lu@gmail.com>
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