Re: more descriptive message for process termination due to max_slot_wal_keep_size

(I noticed I sent a wrong version..)

At Tue, 6 Sep 2022 10:54:35 +0200, "Drouvot, Bertrand" <bdrouvot(at)amazon(dot)com> wrote in
> Thanks for the new patch version!. I did not realized (sorry about
> that) that we'd need to expose byte_size_pretty(). Now I wonder if we

I didn't think we need the units larger than MB, but I used
pretty_print to prevent small number from rounding to exactly zero. On
the other hand, in typical cases it is longer than 6 digits in bytes,
which is a bit hard to read a glance.

> LOG: terminating process 16034 to release replication slot "rep1" because its restart_lsn 0/3158000 exceeds the limit by 15368192 bytes

> should not simply report the number of bytes (like I can see it is
> done in many places). So something like:
..
> + (errmsg("terminating process %d to release replication slot \"%s\"
> because its restart_lsn %X/%X exceeds the limit by %lu bytes",
..
> and then forget about exposing/using byte_size_pretty() (that would be
> more consistent with the same kind of reporting in the existing code).
>
> What do you think?

An alterntive would be rounding up to the whole MB, or a sub-MB.

> ereport(LOG,
> (errmsg("terminating process %d to release replication slot \"%s\" because its restart_lsn %X/%X exceeds the limit by %.1lf MB",
> active_pid, NameStr(slotname),
> LSN_FORMAT_ARGS(restart_lsn),
> /* round-up at sub-MB */
> ceil((double) (oldestLSN - restart_lsn) / 1024 / 102.4) / 10),

> LOG: terminating process 49539 to release replication slot "rep1" because its restart_lsn 0/3038000 exceeds the limit by 15.8 MB

If the distance were 1 byte, it is shown as "0.1 MB".

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center