Re: more descriptive message for process termination due to max_slot_wal_keep_size

On Tue, Dec 14, 2021 at 9:35 AM Kyotaro Horiguchi
<horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> Hello.
>
> As complained in pgsql-bugs [1], when a process is terminated due to
> max_slot_wal_keep_size, the related messages don't mention the root
> cause for *the termination*. Note that the third message does not
> show for temporary replication slots.
>
> [pid=a] LOG: "terminating process %d to release replication slot \"%s\""
> [pid=x] LOG: FATAL: terminating connection due to administrator command
> [pid=a] LOG: invalidting slot "s" because its restart_lsn X/X exceeds max_slot_wal_keep_size
>
> The attached patch attaches a DETAIL line to the first message.
>
> > [17605] LOG: terminating process 17614 to release replication slot "s1"
> + [17605] DETAIL: The slot's restart_lsn 0/2C0000A0 exceeds max_slot_wal_keep_size.
> > [17614] FATAL: terminating connection due to administrator command
> > [17605] LOG: invalidating slot "s1" because its restart_lsn 0/2C0000A0 exceeds max_slot_wal_keep_size
>
> Somewhat the second and fourth lines look inconsistent each other but
> that wouldn't be such a problem. I don't think we want to concatenate
> the two lines together as the result is a bit too long.
>
> > LOG: terminating process 17614 to release replication slot "s1" because it's restart_lsn 0/2C0000A0 exceeds max_slot_wal_keep_size.
>
> What do you think about this?
>
> [1] https://www.postgresql.org/message-id/20211214.101137.379073733372253470.horikyota.ntt%40gmail.com

+1 to give more context to the "terminating process %d to release
replication slot \"%s\"" message.

How about having below, instead of adding errdetail:
"terminating process %d to release replication slot \"%s\" whose
restart_lsn %X/%X exceeds max_slot_wal_keep_size"?

I think we can keep the "invalidating slot \"%s\" because its
restart_lsn %X/%X exceeds max_slot_wal_keep_size" message as-is. We
may not see "terminating process ..." and "invalidation slot ..."
messages together for the same slot, so having slightly different
wording is fine IMO.

Regards,
Bharath Rupireddy.