Re: Syncrep and improving latency due to WAL throttling

Andres Freund <andres@anarazel.de>

From: Andres Freund <andres@anarazel.de>

To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>

Cc: Jakub Wartak <jakub.wartak@enterprisedb.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>

Date: 2023-01-27T21:20:39Z

Lists: pgsql-hackers

Hi,

On 2023-01-27 12:48:43 +0530, Bharath Rupireddy wrote:
> Looking at the patch, the feature, in its current shape, focuses on
> improving replication lag (by throttling WAL on the primary) only when
> synchronous replication is enabled. Why is that? Why can't we design
> it for replication in general (async, sync, and logical replication)?
> 
> Keeping replication lag under check enables one to provide a better
> RPO guarantee as discussed in the other thread
> https://www.postgresql.org/message-id/CAHg%2BQDcO_zhgBCMn5SosvhuuCoJ1vKmLjnVuqUEOd4S73B1urw%40mail.gmail.com.

I think something narrower and easier to achieve is a good thing. We've
already had loads of discussion for the more general problem, without a lot of
actual progress.

Greetings,

Andres Freund