Re: Errors on missing pg_subtrans/ files with 9.3

On Fri, Nov 15, 2013 at 3:21 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> I think what would help the most is if you could arrange to obtain a
> stack backtrace at the point when the error is thrown. Maybe put a
> long sleep call in just before the error happens, and when it gets
> stuck there, attach gdb and run bt full.
>

That could potentially be doable. Perhaps I could use something like
google-coredumper or something similar to have a core dump generated
if the error comes up? Part of the problem is that the error is so
sporadic that it's going to be tough to say when the next one will
occur. For instance, we haven't changed our load on the server, yet
the error hasn't occurred since Nov 13, 15:01. I'd also like to avoid
blocking on the server with sleep or anything like that unless
absolutely necessary, as there are other services we have in
development that are using other databases on this cluster. (I can as
a matter of last resort, of course, but if google-coredumper can do
the job I'd like to give that a shot first.)

Any hints on where I could insert something like this? Should I try
putting it into the section of elog.c dealing with ENOENT errors, or
try to find a spot closer to where the file itself is being opened? I
haven't looked at Postgres internals for a while now so I'm not quite
sure of the best location for this sort of thing.

Cheers