Mutex, Postgres PDO Driver version 1.2.0 was released.
Full-width advisory lock keys ¶
PgsqlMutex now derives two signed 32-bit PostgreSQL advisory-lock keys from the first eight bytes of the SHA-1 hash of the mutex name, instead of two unsigned 16-bit keys from the first four bytes. The larger 64-bit keyspace reduces accidental contention between unrelated mutex names; hash collisions are still possible.
The public API is unchanged. No persistent database data needs migrating; the change affects session-level advisory locks.
Required coordinated transition ¶
The PostgreSQL keys for existing mutex names change. Old and new mappings do not coordinate: workers on the old mapping and workers on the new mapping can hold different advisory locks for the same mutex name at the same time, so exclusion for the same name is broken while both mappings run.
Before starting any process with the new mapping, stop or drain all old-mapping processes that coordinate through these mutexes and let them finish their protected operations and release their locks. This includes web processes, queue workers, scheduled jobs and other applications sharing the same locks. Do not overlap old and new mappings during a rolling deployment.
When rolling back to the old mapping, apply the same transition in reverse: stop or drain all new-mapping processes first, then start the old ones. Never run old and new mappings together while same-name exclusion is required.