Re: syslog facilites and postgres ?

"Day, David" <dday(at)redcom(dot)com> writes:
> Should I be able to run two syslog facilities simultaneously ( postgres local0, and a trigger function to local3 ) successfully ?

Probably not. libc's support for writing to syslog is not re-entrant.

> I have created an insert trigger on one of my datatables using plperlu that opens syslog to facility local3 which directs
> portions of that newly inserted record to local3. ( see below). This works with the the following issue.

> I find occasional notifications in my local3 log file that should I believe be in the local0 log file. E.g. I will see some of
> my RAISE LOG output in the local3 output log file rather than in the local0 output log file. I suspect this is happening
> during the window in which local3 is open and closed in the trigger function. I note that the errant notification I find in local3 is not also found
> in local0.

TBH, I'm astonished that this doesn't break logging to local0 entirely.
Quite aside from the effect you're complaining of, I'd expect it to bollix
subsequent syslog output. After your closelog(), the next syslog() call
would do an implicit openlog(), but with default parameters --- or so I'd
expect anyway.

You could probably un-break that aspect by duplicating Postgres' normal
openlog call after closing the local3 descriptor:

openlog(syslog_ident ? syslog_ident : "postgres",
LOG_PID | LOG_NDELAY | LOG_NOWAIT,
syslog_facility);

but this seems awfully fragile, and it certainly won't do anything for
any messages Postgres tries to emit while you've got the syslog connection
redirected to local3.

Do you really need to have it work like that?

regards, tom lane