Re: Re: Sure enough, the lock file is gone

Tom Lane wrote:
> Lamar Owen <lamar.owen@wgcr.org> writes:
> > But my issue is that libpq or any other client should be smart enough to
> > not have to assume the location.
> Er, how do you propose to do that?  The client cannot learn the correct
> location from the postmaster --- it must figure out *on its own* where
> the socket file is.  AFAICS you can't avoid having hardwired knowledge
> about how to do that in the client.

How does netstat find out?  A simple 
netstat -a --unix|grep \.s\.PGSQL
will get the full list of all postmaster sockets.  A little 'cut' or
'awk' work is simple enough.

I realize, of course, that netstat (and the underlying, on Linux,
/proc/net/unix file) is not portable. On Linux, simply grep
/proc/net/unix for the .s.PGSQL pattern and get the last column (or the
column before that, with the inode information).

Is there a portable way of listing the open unix domain sockets in this
manner, then deducing from the socket path what you need to know?

> You or somebody else previously suggested hardwiring the location of
> a configuration file, rather than the socketfile itself, but I can't
> see that that really improves matters in this context.  In particular,
> changing to such a method would still break backwards compatibility.

Not me.  The less hardwiring, the better, IMHO. And I'm glad you pointed
me to the new (undocumented that I could find) usage of PGHOST.  A
dynamic socket finder (assuming no specific socket path has been passed)
would not break backwards compatibility, as it would find the default
/tmp case.
--
Lamar Owen
WGCR Internet Radio
1 Peter 4:11