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Re: Postgresql, number of connections and life time

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Juan Miguel <juanmime(at)ono(dot)com>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: Postgresql, number of connections and life time
Date: 2006-01-28 16:00:41
Message-ID: 11868.1138464041@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-admin
Juan Miguel <juanmime(at)ono(dot)com> writes:
> I have a Linux box with postgres 7.4 branche, where web php applications 
> queries the DB. When Apache launches a php file that connects to the DB, 
> if I do "ps aux | grep postgrest", I can see a process "postgres user 
> ...." running, that represents the session openned to the DB. But when 
> the php program finishes, and closes the connection, this process does 
> not end. Therefore the number of processes are growing while people 
> visit the web.  Why ?

Evidently the connection isn't really getting closed.  I don't know
enough about PHP to help you with why not, though.

> I gain access this DB remotely by an encrypted connection with stunnel. 
> Well, when I launch a connection to a DB, and passes a long time without 
> traffic, I realise the connection is closed. The program that queries 
> the DB does not realise the connection is broken and when it tries to 
> query, it fails. I think that the origin of the problem is not stunnel, 
> because the same problem presents to me when trying with a testing DB 
> without stunnel.  Why ? Has postgres a timer that breaks the 
> connections when there is no traffic ? Has Linux this timmer ?

No, and no, but a lot of router and firewall hardware has idle-timeouts
for connections.  Look at the settings for whatever boxes are between
your two machines --- if you're lucky, you can increase the idle
timeout.

More recent versions of PG (I think 8.1 and up) allow you to fool with
the TCP keepalive settings --- reducing those can be used to generate
dummy traffic that will keep the firewall from thinking the connection
is idle.

			regards, tom lane

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