On Tue, Jun 25, 2024 at 05:01:55PM +0200, Anthonin Bonnefoy wrote: > During backend initialisation, pgStat DSA is attached using > dsa_attach_in_place with a NULL segment. The NULL segment means that > there's no callback to release the DSA when the process exits. > pgstat_detach_shmem only calls dsa_detach which, as mentioned in the > function's comment, doesn't include releasing and doesn't decrement the > reference count of pgStat DSA. > > Thus, every time a backend is created, pgStat DSA's refcnt is incremented > but never decremented when the backend shutdown. It will eventually > overflow and reach 0, triggering the "could not attach to dynamic shared > area" error on all newly created backends. When this state is reached, the > only way to recover is to restart the db to reset the counter.
Very good catch! It looks like you have seen that in the field, then. Sad face. > This patch fixes this issue by releasing pgStat DSA with > dsa_release_in_place during pgStat shutdown to correctly decrement the > refcnt. Sounds logic to me to do that in the pgstat shutdown callback, ordered with the dsa_detach calls in a single location rather than registering a different callback to do the same job. Will fix and backpatch, thanks for the report! -- Michael
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