On Mon, 6 May 2002, Tom Lane wrote:
> I said:
> > But the backends would only have the socket open, they'd not be actively
> > listening to it. So how could you tell whether anyone had the socket
> > open or not?
>
> Oh, I take that back, I see how you could do it: the postmaster opens
> the socket *for writing*, but never actually writes. All its child
> processes inherit that same open file descriptor and just keep it
> around. Then, to tell if anyone's home, you open the socket *for
> reading* and try to read in O_NONBLOCK mode. You get an EOF indication
> if and only if no one has the socket open for writing; otherwise you
> get an EAGAIN error.
>
> That would work ... but is it more portable than depending on SysV
> shmem connection counts? ISTR that some of the platforms we support
> don't have Unix-style sockets at all.
Wouldn't the same thing work with a simple file? Does it have to be a
UnixDomainSocket?
