Re: more descriptive message for process termination due to max_slot_wal_keep_size

Hi,

(I noticed I sent a wrong version..)

At Tue, 6 Sep 2022 10:54:35 +0200, "Drouvot, Bertrand" <bdrouvot@amazon.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. 

Yeah makes sense.

Also, rounding to zero wouldn't occur with "just" displaying "oldestLSN - restart_lsn" (as proposed upthread).

On
the other hand, in typical cases it is longer than 6 digits in bytes,
which is a bit hard to read a glance.

Yeah right, but that's already the case in some part of the code, like for example in arrayfuncs.c:

                ereport(ERROR,
                        (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                         errmsg("array size exceeds the maximum allowed (%d)",
                                (int) MaxAllocSize)));

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),

typo "/ 102.4" ?

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".

Right and I'm -1 on it, I think we should stick to the "pretty" or the "bytes only" approach (my preference being the bytes only one).

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com