Re: Multiple UNIX-domain sockets?

Tom Lane wrote:
> Oliver Fromme writes:
> > I need to run a postgresql server with multiple UNIX-domain
> > sockets, i.e. not just the one in /tmp. Is that possible
> > at all?
>
> No ... why would you need it?

See below.

> (The postmaster could probably be made to do this if it was important,
> but I don't see the use-case.)
>
> > (I had the idea to create hardlinks to the socket in /tmp,
> > but unfortunately /tmp is a separate file system on a
> > memory disk, so it's not possible to create hardlinks to
> > somewhere else.)
>
> Wouldn't a symlink work?

No, it wouldn't. I'm sorry, I should have explained why
I need it in the first place.

My operating system is FreeBSD, and it supports a feature
called "jails" which is similar to chroot, but has a lot
of additional functionality (separate process spaces and
other things). I would like to run an untrustworthy
application within such a jail. The application needs to
access a database, for which I will be using PostgreSQL.
However, I do not want to install postgres within the same
jail, because I intend to use it for other purposes, too.
In the future there might be a another application in a
different jail, which also accesses a postgres database.

Well, because of the chrooted environment, the application
cannot access postgres' socket in /tmp. Hardlinks don't
work because they're separate filesystems. Symlinks don't
work because a symlink cannot point to an object outside
of a jail.

The only solution would be to use TCP sockets on localhost,
but the TCP/IP overhead is considerably higher, especially
when there are lots of small queries (which I expect).
I've foiund several benchmarks in various mailinglists,
some mention a factor of 10.

Therefore I would definitely prefer to use UNIX-domain
sockets instead, if possible.

Best regards
Oliver

--
Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.

PI:
int f[9814],b,c=9814,g,i;long a=1e4,d,e,h;
main(){for(;b=c,c-=14;i=printf("%04d",e+d/a),e=d%a)
while(g=--b*2)d=h*b+a*(i?f[b]:a/5),h=d/--g,f[b]=d%g;}