Consider creating a pg_stat_activity history table. This would allow you to look back at the time of incident and verify if any unusual activity was occurring in the database. Something like:
CREATE TABLE pg_stat_activity_hist AS SELECT now() AS sample_time, a.* FROM pg_stat_activity a WITH NO data;
Then with a cron job or a pg job scheduler insert the pg_stat_activity history at some desired interval (e.g 30s, 1m or 5m):
INSERT INTO pg_stat_activity_hist
SELECT
now(),
a.*
FROM
pg_stat_activity a
WHERE
state IN ('active', 'idle in transaction’);
Then regularly purge any sample_times older than some desired interval (1 day, 1 week, 1 month).
Not a perfect solution because the problem (if a db problem) could occur between your pg_stat_activity samples. We keep this kind of history and it is very helpful when trying to find a post-event root cause.
Craig
On Jan 30, 2023 at 10:47:49 AM, Mok <gurmokh@xxxxxxxxx> wrote:
Hi,We've started to observe instances of one of our databases stalling for a few seconds.We see a spike in wal write locks then nothing for a few seconds. After which we have spike latency as processes waiting to get to the db can do so.There is nothing in the postgres logs that give us any clues to what could be happening, no locks, unusually high/long running transactions, just a pause and resume.Could anyone give me any advice as to what to look for when it comes to checking the underlying disk that the db is on?Thanks,Gurmokh
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