On Wed, Oct 23, 2013 at 12:11:39PM -0500, andy wrote: - On 10/23/2013 11:07 AM, David Kerr wrote: - >On Tue, Oct 22, 2013 at 12:41:58PM -0500, andy wrote: - >- Hi all. - >- - >- My website is about to get a little more popular. I'm trying to add in - >- some measurements to determine an upper limit of how many concurrent - >- database connections I'm currently using. - >- - >- I've started running this: - >- - >- SELECT sum(numbackends) AS count, sum(xact_commit) as ttlcommit FROM - >- pg_stat_database; - >- - >- Every 10 seconds or so. I don't think its what I want though. It seems - >- way too small. I'm guessing that its not a measure of the previous 10 - >- seconds. Its a count of how many backends are in use at the exact - >- moment I run the sql. - >- - >- Is there a cumulative count someplace? - >- - >- Thanks for your time, - >- - >- -Andy - > - >You've gotten good info from the other guys on how to scale your're DB - >but to answer you're original question. I usually use this query: - > - >select count(*) from pg_stat_activity where state <> 'idle'; - > - >That gives you the # of "active" connections to your database and is - >something you want to try to get good metrics on. - > - >Idle connections have some overhead but if Active > # of CPUs your - >performance - >starts to degrade. Now, really that's pretty normal but, ideally, you need - >to - >know what the ratio of Active Connections to # CPUs still gives you - >acceptable - >performance. And that's really based on your app and hardware. - > - > - - How often do you run that? Once a second? And graph it? I was doing - it every 10 seconds, but it doesn't give me a good view of the system. I actually have it as a munin module so it runs every few minutes. If I'm actually doing a performance test or something I would run it every second or every 5 / 10 seconds. The knowledge is only really useful if you have a good trend built up so you know how your app responds to having a certian # of active connections. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
