Re: Can postgresql accept mutliple connections in the same

Neil Conway wrote:

>On Fri, 2004-11-19 at 16:17 +1300, Dru wrote:
>  
>
>>Though one of hte developers
>>tells me that sometimes it gets a link resource allocation error on 
>>opening connections to the database server which i dont know if that is 
>>related.  
>>    
>>
>
>I'm not sure what you mean by a "link resource allocation error". Can
>you provide the exact error message you get when a connection is
>refused? (Try checking the PostgreSQL logfile.)
>  
>
I'll get the developer to write down the exact error when it happens again.
I think he only gets it once or twice a week when using the database
server and grown accustomed to it.  I myself when testing the database
server for errors dont get any at all when connections fail when they 
shouldnt fail :( .

>>Max connections is set to 500, the webpage for the server code 
>>initalises and then closes the connection when its done.
>>    
>>
>
>It might be worth considering connection pooling or persistent
>connections, although that shouldn't be related to the specific problem
>you're having.
>  
>
I was using persistent connections initally and was getting this problem
so switched to non-persistant and made sure i was cleaning them up 
afterwards
in case it helped solved this problem.  I've replaced the db server and 
webserver
also to try and resolve it but that had no effect.  I initally thought 
it might
be something to do with a kernel limit on sockets or something to that 
effect.
These connections are all TCP/IP based.

>>Does pg_dumpall or pg_dump lock the database block access 
>>to the database so you cant create connections?
>>    
>>
>No.
>  
>
Ok that rules out that possibility then.

>>Could it be possible 
>>postgresql can only create one connection at a time and if it gets two 
>>requests for a connection at the same time it fails?
>>    
>>
>
>No.
>  
>

Ok rules out that possibility also.  Is there any stress testing 
software for
postgresql to find out how and when it breaks?   I wrote a simple script
to simulate 300 concurrent users on the webfrontend which breaks
the website real quick with 1 in 10 connections to db failing with no error
returned by connect just a dead connection.  The website uses php,
the problem could be in the wrapper code for PHP though. I havnt
got much luck asking php developers about the problem though.