Re: Unwanted persisting connections

On Mon, 21 Nov 2005, Andrew McMillan wrote:

> 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!

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.
>
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