Re: Ability to listen on two unix sockets

On sön, 2012-06-10 at 17:35 -0400, Tom Lane wrote:
> I'm unconvinced that allowing multiple port numbers is worth the
> amount of confusion it will cause.

Well, it's a feature that people have asked for. I would love to have
it. Much more than multiple Unix-domain socket locations.

> In particular, we've traditionally
> used "the port number" as part of the key for resources such as shared
> memory.

But it hasn't been a requirement for a long time that those match up
exactly. It's already possible that they don't, if you configure
postmasters with the same port and non-conflicting IP addresses or
Unix-socket locations.

> I think we'd want the number used for that purpose to be what
> is written into the lock file ... but then what if the postmaster is
> not actually listening on *any* actual socket with that number?
> pg_ctl will not be happy.
>
I'm not sure why pg_ctl needs to know about the shared memory business.
We write the shared memory key into the lock file, so the port number in
the lock file should just be a port number for pg_ctl to use. Of course
you can configure things so that pg_ctl cannot contact the postmaster,
but this problem already exists in a more likely fashion with
listen_addresses. Adding an extra port doesn't make it more likely.