Re: Why is hot_standby_feedback off by default?

On Sun, Oct 22, 2023 at 4:56 AM Vik Fearing <vik(at)postgresfriends(dot)org> wrote:

> On 10/22/23 09:50, sirisha chamarthi wrote:
> > Is there any specific reason hot_standby_feedback default is set to off?
>
>
> Yes. No one wants a rogue standby to ruin production.
>

Agreed. I believe that any reasonable use of a standby server for queries
requires hot_standby_feedback to be turned on. Otherwise, we can
potentially see query cancellations, increased replication lag because of
conflicts (while replaying vacuum cleanup records) on standby (resulting in
longer failover times if the server is configured for disaster recovery +
read scaling). Recent logical decoding on standby as well requires
hot_standby_feedback to be turned on to avoid slot invalidation [1]. If
there is no requirement to query the standby, admins can always set
hot_standby to off. My goal here is to minimize the amount of configuration
tuning required to use these features.

[1]:
https://www.postgresql.org/docs/current/logicaldecoding-explanation.html

Thanks,
Sirisha