Re: Time delayed LR (WAS Re: logical replication restrictions)

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>
Cc: Euler Taveira <euler(at)eulerto(dot)com>, "osumi(dot)takamichi(at)fujitsu(dot)com" <osumi(dot)takamichi(at)fujitsu(dot)com>, Melih Mutlu <m(dot)melihmutlu(at)gmail(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Marcos Pegoraro <marcos(at)f10(dot)com(dot)br>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Peter Smith <smithpb2250(at)gmail(dot)com>
Subject: Re: Time delayed LR (WAS Re: logical replication restrictions)
Date: 2022-11-14 10:15:23
Message-ID: CAA4eK1KHAAX+bhFV1G1vYTRtiLsFZKTVNELJYt7uC3jdzPooFw@mail.gmail.com
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On Wed, Nov 9, 2022 at 12:11 PM Kyotaro Horiguchi
<horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> At Wed, 10 Aug 2022 17:33:00 -0300, "Euler Taveira" <euler(at)eulerto(dot)com> wrote in
> > On Wed, Aug 10, 2022, at 9:39 AM, osumi(dot)takamichi(at)fujitsu(dot)com wrote:
> > > Minor review comments for v6.
> > Thanks for your review. I'm attaching v7.
>
> Using interval is not standard as this kind of parameters but it seems
> convenient. On the other hand, it's not great that the unit month
> introduces some subtle ambiguity. This patch translates a month to 30
> days but I'm not sure it's the right thing to do. Perhaps we shouldn't
> allow the units upper than days.
>

Agreed. Isn't the same thing already apply to recovery_min_apply_delay
for which the maximum unit seems to be in days? If so, there is no
reason to do something different here?

> apply_delay() chokes the message-receiving path so that a not-so-long
> delay can cause a replication timeout to fire. I think we should
> process walsender pings even while delaying. Needing to make
> replication timeout longer than apply delay is not great, I think.
>

Again, I think for this case also the behavior should be similar to
how we handle recovery_min_apply_delay.

--
With Regards,
Amit Kapila.

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