| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Sergei Kornilov <sk(at)zsrv(dot)org> |
| Cc: | "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Michael Banck <michael(dot)banck(at)credativ(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Robert Haas <robertmhaas(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Online enabling of checksums |
| Date: | 2018-08-01 18:06:40 |
| Message-ID: | 20180801180640.w2tux7te3dje5qdf@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2018-08-01 21:03:22 +0300, Sergei Kornilov wrote:
> > They fail over to a secondary to do maintenance on a primary.
> But this is not problem even in current patch state. We can restart replica before failover and it works. I tested this behavior during my review.
> We can:
> - call pg_enable_data_checksums() on master
> - wait change data_checksums to inprogress on replica
That's *precisely* the problem. What if your replicas are delayed
(e.g. recovery_min_apply_delay)? How would you schedule that restart
properly? What if you later need to do PITR?
> - restart replica - we can restart replica before promote, right?
> - promote this replica
> - checksum helper is launched now and working on this promoted cluster
This doesn't test the consequences of the restart being skipped, nor
does it review on a code level the correctness.
Greetings,
Andres Freund
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