PHP with PostgreSQL - Unwanted persisting connections

Author

Unwanted persisting connections

Gary Hoffman

2005-11-21, 3:24 am

I've run PHP and PostgreSQL for quite a while and never seen this problem
before. I think it's new, but maybe I never paid attention to it before.

I am frequently running out of connections to the database. Here's a
snippet of my ps -ax

1882 ?? S 0:00.07 postgres: postgres cgssd_members [local] idle

1883 ?? S 0:00.09 postgres: postgres cgssd_members [local] idle

1884 ?? S 0:00.07 postgres: postgres cgssd_members [local] idle

1886 ?? S 0:00.14 postgres: postgres cgssd_members [local] idle

1887 ?? S 0:00.06 postgres: postgres cgssd_members [local] idle

500 std- S 0:01.14 /usr/local/bin/postmaster -D
/usr/local/pgsql/data
501 std- S 0:00.02 postgres: stats buffer process

502 std- S 0:00.21 postgres: stats collector process

As you can see, there are some idle connections that have come in from PHP
on my web pages. I've never seen these before and eventually they build up
and I get an error connecting from the PHP page to the database.

I'm running apache 1.3.33 on Darwin Kernal 7.9.0 (MacOS X 10.3.9) with PHP
4.3.6 and PostgreSQL 7.4.2.

Ideas and suggestions are welcome.

Thanks,
Gary

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* Gary B. Hoffman, Computing Services Manager e-mail: ghoffman@ucsd.edu *
* Graduate School of International Relations and Pacific Studies (IR/PS) *
* University of California, San Diego (UCSD) voice: (858) 534-1989 *
* 9500 Gilman Dr. MC 0519 fax: (858) 534-3939 *
* La Jolla, CA 92093-0519 USA web: http://irps.ucsd.edu/ *
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Andrew McMillan

2005-11-21, 3:24 am

On Sun, 2005-11-20 at 20:06 -0800, Gary Hoffman wrote:
> I've run PHP and PostgreSQL for quite a while and never seen this problem
> before. I think it's new, but maybe I never paid attention to it before.
>
> I am frequently running out of connections to the database. Here's a
> snippet of my ps -ax
>
> 1882 ?? S 0:00.07 postgres: postgres cgssd_members [local] idle
>
> 1883 ?? S 0:00.09 postgres: postgres cgssd_members [local] idle
>
> 1884 ?? S 0:00.07 postgres: postgres cgssd_members [local] idle
>
> 1886 ?? S 0:00.14 postgres: postgres cgssd_members [local] idle
>
> 1887 ?? S 0:00.06 postgres: postgres cgssd_members [local] idle
>
> 500 std- S 0:01.14 /usr/local/bin/postmaster -D
> /usr/local/pgsql/data
> 501 std- S 0:00.02 postgres: stats buffer process
>
> 502 std- S 0:00.21 postgres: stats collector process
>
>
> As you can see, there are some idle connections that have come in from PHP
> on my web pages. I've never seen these before and eventually they build up
> and I get an error connecting from the PHP page to the database.
>
> I'm running apache 1.3.33 on Darwin Kernal 7.9.0 (MacOS X 10.3.9) with PHP
> 4.3.6 and PostgreSQL 7.4.2.

You will have as many of these as you have apache processes. That's
what persistent connections means!

If you have MaxClients set to (e.g.) 150 in your apache configuration,
and you actually get to something like that, then the default PostgreSQL
configuration of 100 clients simply won't be enough. You should
increase it to at leas 20-50 more than the MaxClients setting that
Apache has.

You'll be pleased to know that each extra PostgreSQL connection
typically uses less than each additional apache connection (especially
when you're running PHP et al.) so if you find yourself running out of
RAM you will need to lower the MaxClients setting first.

Regards,
Andrew McMillan.

-------------------------------------------------------------------------
Andrew @ Catalyst .Net .NZ Ltd, PO Box 11-053, Manners St, Wellington
WEB: http://catalyst.net.nz/ PHYS: Level 2, 150-154 Willis St
DDI: +64(4)803-2201 MOB: +64(272)DEBIAN OFFICE: +64(4)499-2267
You will be a winner today. Pick a fight with a four-year-old.
-------------------------------------------------------------------------

Philip Hallstrom

2005-11-21, 8:25 pm

On Mon, 21 Nov 2005, Andrew McMillan wrote:

> On Sun, 2005-11-20 at 20:06 -0800, Gary Hoffman wrote:
>
> You will have as many of these as you have apache processes. That's
> what persistent connections means!

You can end up with a *lot* more than apache's MaxClients if you open
persistent connections with different connection paramaters... so keep
that in mind if you're connecting to more than one database.

You might look at pgpool. Never used it, but it comes up frequently as a
solution to this...

>
> If you have MaxClients set to (e.g.) 150 in your apache configuration,
> and you actually get to something like that, then the default PostgreSQL
> configuration of 100 clients simply won't be enough. You should
> increase it to at leas 20-50 more than the MaxClients setting that
> apache has.
>
> You'll be pleased to know that each extra PostgreSQL connection
> typically uses less than each additional apache connection (especially
> when you're running PHP et al.) so if you find yourself running out of
> RAM you will need to lower the MaxClients setting first.
>
> Regards,
> Andrew McMillan.
>
> -------------------------------------------------------------------------
> Andrew @ Catalyst .Net .NZ Ltd, PO Box 11-053, Manners St, Wellington
> WEB: http://catalyst.net.nz/ PHYS: Level 2, 150-154 Willis St
> DDI: +64(4)803-2201 MOB: +64(272)DEBIAN OFFICE: +64(4)499-2267
> You will be a winner today. Pick a fight with a four-year-old.
> -------------------------------------------------------------------------
>
>

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