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From: Bossart, Nathan <[email protected]>
To: SATYANARAYANA NARLAPURAM <[email protected]>
To: Kyotaro Horiguchi <[email protected]>
Cc: Jeff Davis <[email protected]>
Cc: Bharath Rupireddy <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: Disallow quorum uncommitted (with synchronous standbys) txns in logical replication subscribers
Date: Fri, 7 Jan 2022 18:23:24 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAHg+QDdfjQS6c8JAcV5z+ZfdGCYYm4xDvEFKHGkToGJdT8pd9w@mail.gmail.com>
References: <CAHg+QDc-3bPT52yqB-_J-_8bc6DzpxVVzvQMA99XV_0tqOR9wg@mail.gmail.com>
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On 1/6/22, 11:25 PM, "Jeff Davis" <[email protected]> wrote:
> On Wed, 2022-01-05 at 23:59 -0800, SATYANARAYANA NARLAPURAM wrote:
>> I would like to propose a GUC send_Wal_after_quorum_committed which
>> when set to ON, walsenders corresponds to async standbys and logical
>> replication workers wait until the LSN is quorum committed on the
>> primary before sending it to the standby. This not only simplifies
>> the post failover steps but avoids unnecessary downtime for the async
>> replicas. Thoughts?
>
> Do we need a GUC? Or should we just always require that sync rep is
> satisfied before sending to async replicas?
>
> It feels like the sync quorum should always be ahead of the async
> replicas. Unless I'm missing a use case, or there is some kind of
> performance gotcha.

I don't have a strong opinion on whether there needs to be a GUC, but
+1 for the ability to enforce sync quorum before sending WAL to async
standbys.  I think that would be a reasonable default behavior.

Nathan

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