From: | "Drouvot, Bertrand" <bertranddrouvot(dot)pg(at)gmail(dot)com> |
---|---|
To: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Cc: | vignesh C <vignesh21(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Add two missing tests in 035_standby_logical_decoding.pl |
Date: | 2023-04-25 07:19:43 |
Message-ID: | 8679d9c4-961b-b77f-baa7-718e58f953ff@gmail.com |
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Thread: | |
Lists: | pgsql-hackers |
Hi,
On 4/25/23 6:23 AM, Amit Kapila wrote:
> On Mon, Apr 24, 2023 at 3:36 PM Drouvot, Bertrand
> <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>>
>> Without the second "pg_log_standby_snapshot()" then wait_for_subscription_sync() would be waiting
>> some time on the poll for "SELECT count(1) = 0 FROM pg_subscription_rel WHERE srsubstate NOT IN ('r', 's');"
>>
>> Adding a comment in V3 to explain the need for the second pg_log_standby_snapshot().
>>
>
> Won't this still be unpredictable because it is possible that the
> tablesync worker may take more time to get launched or create a
> replication slot? If that happens after your second
> pg_log_standby_snapshot() then wait_for_subscription_sync() will be
> hanging.
Oh right, that looks like a possible scenario.
> Wouldn't it be better to create a subscription with
> (copy_data = false) to make it predictable and then we won't need
> pg_log_standby_snapshot() to be performed twice?
>
> If you agree with the above suggestion then you probably need to move
> wait_for_subscription_sync() before Insert.
>
I like that idea, thanks! Done in V4 attached.
Not related to the above corner case, but while re-reading the patch I also added:
"
$node_primary->wait_for_replay_catchup($node_standby);
"
between the publication creation on the primary and the subscription to the standby
(to ensure the publication gets replicated before we request for the subscription creation).
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
Attachment | Content-Type | Size |
---|---|---|
v4-0002-Add-retained-WAL-test-in-035_standby_logical_deco.patch | text/plain | 3.8 KB |
v4-0001-Add-subscribtion-to-the-standby-test-in-035_stand.patch | text/plain | 6.1 KB |
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