mirror of
https://github.com/neondatabase/neon.git
synced 2026-01-05 20:42:54 +00:00
8a8b83df27
## Problem Right now if there are too many running xacts to be restored from CLOG at replica startup, then replica is not trying to restore them and wait for non-overflown running-xacs WAL record from primary. But if primary is not active, then replica will not start at all. Too many running xacts can be caused by transactions with large number of subtractions. But right now it can be also cause by two reasons: - Lack of shutdown checkpoint which updates `oldestRunningXid` (because of immediate shutdown) - nextXid alignment on 1024 boundary (which cause loosing ~1k XIDs on each restart) Both problems are somehow addressed now. But we have existed customers with "sparse" CLOG and lack of checkpoints. To be able to start RO replicas for such customers I suggest to add GUC which allows replica to start even in case of subxacts overflow. ## Summary of changes Add `neon.running_xacts_overflow_policy` with the following values: - ignore: restore from CLOG last N XIDs and accept connections - skip: do not restore any XIDs from CXLOGbut still accept connections - wait: wait non-overflown running xacts record from primary node ## Checklist before requesting a review - [ ] I have performed a self-review of my code. - [ ] If it is a core feature, I have added thorough tests. - [ ] Do we need to implement analytics? if so did you add the relevant metrics to the dashboard? - [ ] If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section. ## Checklist before merging - [ ] Do not forget to reformat commit message to not include the above checklist --------- Co-authored-by: Konstantin Knizhnik <knizhnik@neon.tech>