From: | "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com> |
---|---|
To: | 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> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Synchronizing slots from primary to standby |
Date: | 2023-04-14 13:22:26 |
Message-ID: | b5cc7fd2-ebbc-512f-40fc-5c7ce93b8bdf@gmail.com |
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Lists: | pgsql-hackers |
Hi,
On 11/15/22 10:02 AM, Drouvot, Bertrand wrote:
> Hi,
>
> On 2/11/22 3:26 PM, Peter Eisentraut wrote:
>> On 10.02.22 22:47, Bruce Momjian wrote:
>>> On Tue, Feb 8, 2022 at 08:27:32PM +0530, Ashutosh Sharma wrote:
>>>>> Which means that if e.g. the standby_slot_names GUC differs from
>>>>> synchronize_slot_names on the physical replica, the slots synchronized on the
>>>>> physical replica are not going to be valid. Or if the primary drops its
>>>>> logical slots.
>>>>>
>>>>>
>>>>>> Should the redo function for the drop replication slot have the capability
>>>>>> to drop it on standby and its subscribers (if any) as well?
>>>>>
>>>>> Slots are not WAL logged (and shouldn't be).
>>>>>
>>>>> I think you pretty much need the recovery conflict handling infrastructure I
>>>>> referenced upthread, which recognized during replay if a record has a conflict
>>>>> with a slot on a standby. And then ontop of that you can build something like
>>>>> this patch.
>>>>>
>>>>
>>>> OK. Understood, thanks Andres.
>>>
>>> I would love to see this feature in PG 15. Can someone explain its
>>> current status? Thanks.
>>
>> The way I understand it:
>>
>> 1. This feature (probably) depends on the "Minimal logical decoding on standbys" patch. The details there aren't totally clear (to me). That patch had some activity lately but I don't see it in a state that it's nearing readiness.
>>
>
> FWIW, a proposal has been submitted in [1] to add information in the WAL records in preparation for logical slot conflict handling.
>
> [1]: https://www.postgresql.org/message-id/178cf7da-9bd7-e328-9c49-e28ac4701352@gmail.com
>
Now that the "Minimal logical decoding on standby" patch series (mentioned up-thread) has been
committed, I think we can resume working on this one ("Synchronizing slots from primary to standby").
I'll work on a rebase and share it once done (unless someone already started working on a rebase).
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
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