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Zhengchao An
88fa3877c1
Only replication-target writes took the bucket transaction lock. Every other
config write (policy, tagging, lifecycle, versioning, ...) went straight to
the process-local metadata-system guard, which serializes nothing across
nodes.
Each config write is a read-modify-write of one whole BucketMetadata blob:
load the blob, replace one field, save the blob back. The namespace locks
inside read_config/save_config are taken and released separately, so they do
not span that cycle. Two nodes updating different config files of the same
bucket therefore both load the same blob, each set their own field, and the
later save drops the other's -- with both clients already told 2xx. This is
not last-writer-wins on one document; an orthogonal config silently vanishes.
Route update(), delete() and update_config_with() through
acquire_config_write_guards(), which takes the cluster-wide transaction lock
first and the metadata-system write guard second. That order is load-bearing:
taking the process-local guard first would park every local reader and writer
of every bucket behind a lock whose holder may be another node, turning
remote contention into a local stall.
The lock is per bucket rather than per config file, since a per-file key
would let exactly the offending pair run concurrently. Rename the helper to
acquire_bucket_metadata_transaction_lock to match, but deliberately keep the
lock resource string as "bucket-targets/{bucket}/transaction.lock": the key
is what nodes agree on, so renaming it would leave a mixed-version cluster
with two disjoint keys and stop old and new nodes from excluding each other
on the very writes that are serialized today.
update_config_with() already narrowed its staleness window to a single load
and save, but its exclusion was explicitly process-local; it is now
cluster-wide, so its doc comment no longer disclaims cross-node races.
Also make update_and_parse load through self.api instead of the ambient store
handle, so the read and the write of one read-modify-write cannot resolve to
different instances.
The new tests drive two BucketMetadataSys instances over one ECStore -- the
in-process stand-in for two nodes, since they share no RwLock and can only be
serialized by the namespace lock. Verified the lost-update test has teeth by
removing the lock and confirming it fails on round 0, with the tagging config
clobbered to empty by the concurrent policy write.