Re: process type escape for log_line_prefix

On 2016-10-14 13:11:51 +0200, Christoph Berg wrote:
> Re: Michael Paquier 2016-02-10 <CAB7nPqS=wBbZzBcty1KyN-5Y9bPXZ+deJbfcCtebf06eF2Uyvg(at)mail(dot)gmail(dot)com>
> > On Mon, Feb 8, 2016 at 11:32 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> > > Frequently when reading postgres logs to do some post mortem analysis
> > > I'm left wondering what process emitted an error/log message. After the
> > > fact it's often hard to know wether an error message was emitted by a
> > > user backend or by something internal, say the checkpointer or
> > > autovacuum. Logging all process starts is often impractical given the
> > > log volume that causes.
> > >
> > > So I'm proposing adding an escape displaying the process title (say 'k'
> > > for kind?). So %k would emit something like "autovacuum worker process",
> > > "wal sender process" etc.
> >
> > It would be nice to get something consistent between the ps output and
> > this new prefix, say with for example a miscadmin.h parameter like
> > MyProcName.
> >
> > > I'm thinking it might make sense to give normal connections "" as the
> > > name, they're usually already discernible.
> >
> > Yeah, that sounds fine for me. What about background workers? I would
> > think that they should use BackgroundWorker->bgw_name.
>
> (Rediscovering an old horse)
>
> Couldn't these processes just set %a = application_name?

It'd not get me what I'd want, no. E.g for walsenders that'd not be
parsable in a meaningful way. I really would like an escape that'd
always output one of:
Postmaster, Startup, BgWriter, Checkpointer, WalWriter, WalReceiver,
AutovacLauncher, AutovacWorker, PgArch, PgStat, SysLogger, Backend,
BackgroundWorker.

Greetings,

Andres Freund