Re: total number of concurrent connections

Lonni J Friedman <netllama(at)gmail(dot)com> writes:
> On Sun, Jul 26, 2009 at 1:23 PM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> pg_stat_activity should be reasonably trustworthy, modulo the fact that
>> the display might be a fraction of a second out-of-date.

> Hrmm, that's not what I'm seeing. I'm finding that connections
> continue to appear in the table long after I've terminated a remote
> pqsl connection. I'm talking minutes or even hours.

What are you doing to "terminate" these remote connections? What it
sounds like is the connected server process isn't being told about the
termination, and so it sits there waiting for input that will never
come. We do enable TCP keepalive if available, so unless your server
is running a seriously obsolete OS, it will eventually figure out the
client is gone --- but that takes order-of-hours with the standard TCP
timeout settings.

Between that and your unreasonably large number of TIME_WAIT
connections, it definitely seems like you've got TCP-level connection
reliability problems. TIME_WAIT state should go away pretty fast too
if things are working properly at the network level. I wonder whether
you have a router that is dropping connections it thinks are idle.
Beyond that my TCP expertise does not extend.

regards, tom lane