Re: [PATCH] Note effect of max_replication_slots on subscriber side in documentation.

On Thu, Feb 25, 2021 at 2:19 AM Paul Martinez <paulmtz(at)google(dot)com> wrote:
>
> Hey, all,
>
> I went ahead and made a patch for introducing a new GUC variable,
> max_replication_origins, to replace the awkward re-use of
> max_replication_slots.
>
> I'm mostly indifferent whether a new GUC variable is necessary, or
> simply just updating the existing documentation (the first patch I
> sent) is sufficient, but one of them should definitely be done to
> clear up the confusion.
>

+1. I also think one of them is required. I think users who are using
cascaded replication (means subscribers are also publishers), setting
this parameter might be a bit confusing and difficult. Anybody else
has an opinion on this matter?

For docs only patch, I have few suggestions:
1. On page [1], it is not very clear that we are suggesting to set
max_replication_slots for origins whereas your new doc patch has
clarified it, can we update the other page as well.
2.
Setting it a lower value than the current
+ number of tracked replication origins (reflected in
+ <link
linkend="view-pg-replication-origin-status">pg_replication_origin_status</link>,
+ not <link
linkend="catalog-pg-replication-origin">pg_replication_origin</link>)
+ will prevent the server from starting.
+ </para>

Why can't we just mention pg_replication_origin above?

[1] - https://www.postgresql.org/docs/13/logical-replication-config.html

--
With Regards,
Amit Kapila.