| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Jeff Davis <pgsql(at)j-davis(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Ibrar Ahmed <ibrar(dot)ahmad(at)gmail(dot)com>, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, fabriziomello(at)gmail(dot)com, tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>, Rahila Syed <rahila(dot)syed(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Melanie Plageman <melanieplageman(at)gmail(dot)com> |
| Subject: | Re: Minimal logical decoding on standbys |
| Date: | 2023-04-05 00:43:44 |
| Message-ID: | 20230405004344.fzaniqscgrb33rzb@awork3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2023-04-04 17:33:25 -0700, Jeff Davis wrote:
> On Tue, 2023-04-04 at 14:55 -0400, Robert Haas wrote:
> > That's presumably OK, in the
> > sense that they'll go back to sleep and eventually wake up again, but
> > it means they might end up chronically behind sending out WAL to
> > cascading standbys.
>
> Without 0004, cascading logical walsenders would have worse wakeup
> behavior than logical walsenders on the primary. Assuming the fix is
> small in scope and otherwise acceptable, I think it belongs as a part
> of this overall series.
FWIW, personally, I wouldn't feel ok with committing 0003 without 0004. And
IMO they ought to be committed the other way round. The stalls you *can* get,
depending on the speed of WAL apply and OS scheduling, can be long.
This is actually why a predecessor version of the feature had a bunch of
sleeps and retries in the tests, just to avoid those stalls. Obviously that's
not a good path...
Greetings,
Andres Freund
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