From: | "Zhijie Hou (Fujitsu)" <houzj(dot)fnst(at)fujitsu(dot)com> |
---|---|
To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Cc: | shveta malik <shveta(dot)malik(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, Ajin Cherian <itsajin(at)gmail(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Nisha Moond <nisha(dot)moond412(at)gmail(dot)com>, "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>, Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)enterprisedb(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
Subject: | RE: Synchronizing slots from primary to standby |
Date: | 2024-02-27 01:42:59 |
Message-ID: | OS0PR01MB571654A0288C53A676051AE794592@OS0PR01MB5716.jpnprd01.prod.outlook.com |
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Lists: | pgsql-hackers |
On Monday, February 26, 2024 1:19 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, Feb 23, 2024 at 4:45 PM Bertrand Drouvot
> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
> >
> > On Fri, Feb 23, 2024 at 09:46:00AM +0000, Zhijie Hou (Fujitsu) wrote:
> > >
> > > Besides, I'd like to clarify and discuss the behavior of standby_slot_names
> once.
> > >
> > > As it stands in the patch, If the slots specified in
> > > standby_slot_names are dropped or invalidated, the logical walsender
> > > will issue a WARNING and continue to replicate the changes. Another
> > > option for this could be to have the walsender pause until the slot
> > > in standby_slot_names is re-created or becomes valid again. Does anyone
> else have an opinion on this matter ?
> >
> > Good point, I'd vote for: the only reasons not to wait are:
> >
> > - slots mentioned in standby_slot_names exist and valid and do catch
> > up or
> > - standby_slot_names is empty
> >
> > The reason is that setting standby_slot_names to a non empty value
> > means that one wants the walsender to wait until the standby catchup.
> > The way to remove this intentional behavior should be by changing the
> > standby_slot_names value (not the existence or the state of the slot(s) it
> points too).
> >
>
> It seems we already do wait for the case when there is an inactive slot as per the
> below code [1] in the patch. So, probably waiting in other cases is also okay and
> also as this parameter is a SIGHUP parameter, users should be easily able to
> change its value if required. Do you think it is a good idea to mention this in
> docs as well?
>
> I think it is important to raise WARNING as the patch is doing in all the cases
> where the slot is not being processed so that users can be notified and they can
> take the required action.
Agreed. Here is the V99 patch which addressed the above.
This version also includes:
1. list_free the slot list when reloading the list due to GUC change.
2. Refactored the validate_standby_slots based on Shveta's suggestion.
3. Added errcode for the warnings as most of existing have errcodes.
Amit's latest comments[1] are pending, we will address that in next version.
Best Regards,
Hou zj
Attachment | Content-Type | Size |
---|---|---|
v99-0002-Document-the-steps-to-check-if-the-standby-is-re.patch | application/octet-stream | 7.0 KB |
v99-0001-Allow-logical-walsenders-to-wait-for-the-physica.patch | application/octet-stream | 37.1 KB |
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