Understand Mutixact Offset LWLock database contention
Description
Today on 7th of September we had experienced an severity2 incident related to PostgreSQL statement timeouts.
Production incident
One symptom (or a cause) was elevated number of multixact_offset LWLocks sampled from pg_stat_activity during that time:
We also saw a reduced transactions rate and growing txid xmin age.
Proposal
Understand the mechanism behind multixact offset locking leading to the database contention.
Edited by Grzegorz Bizon