Re: Possible causes of high_replay lag, given replication settings?
| От | Greg Sabino Mullane |
|---|---|
| Тема | Re: Possible causes of high_replay lag, given replication settings? |
| Дата | |
| Msg-id | CAKAnmm+jtytmNAYDjBkiQvCHQVwtskUzvp3J_=5mUsFvaOkRVA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Possible causes of high_replay lag, given replication settings? (Jon Zeppieri <zeppieri@gmail.com>) |
| Ответы |
Re: Possible causes of high_replay lag, given replication settings?
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| Список | pgsql-general |
On Fri, Jul 25, 2025 at 9:57 AM Jon Zeppieri <zeppieri@gmail.com> wrote:
Thanks for the response, Nick. I'm curious why the situation you describe wouldn't also lead to the write_lag and flush_lag also being
high. If the problem is simply keeping up with the primary, wouldn't you expect all three lag times to be elevated?
No - write and flush are pretty quick and simple, it's just putting the WAL onto the local disk. Replay involves a lot more work as we have to parse the WAL and apply the changes, which means doing a lot of I/O across many files. Still, *hours* to me indicates more than just a lot of extra traffic. Check that recovery_min_apply_delay is still 0, then log onto the replica and see what's going on with regards to open transactions and locks.
Cheers,
Greg
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