I have postgres set to a max connection limit of 512. I have nearly 30,000 users that will be taking a training course over the next 6 weeks. I have 3 web servers load balanced serving php content for this website. Last week I had postgres set to a connection limit of 128 and that was reached. Since then I have set it to 512 and not had a problem. However, I am unaware of any good monitoring tools that let me see live connections to the database. When I run netstat-c on the db server, it lets me see active connection in real time. Heres an example:
Tcp 0 0 server:postgres 192.168.50.x:port number ESTABLISHED
I will have anywhere from 5 to 7 of these going at any given time. However most say TIME_WAIT instead of established.
I am assuming these are connections to the database that php is using to post and retrieve data. I recently read where postgres uses one semaphore per connection in sets of 16. With that being said is one of these connections that I see in netstat-c actually representing 16 connections? If that is the case, when 6 or 7 are being displayed at once, then that would mean roughly 112 or so connections, which is great because it doesn't even come close to my limit of 512. Can anyone confirm that what I am thinking is right?
Also, is there a way to make the TIME_WAIT status shorter. It seems to exist for about 25 seconds, then goes away. However, those are connections that could easily be used.
Thank you,
Darryl