Re: commons dbcp or pool problems

[Glenn Nielsen]

"Waldhoff, Rodney" wrote:
> 
> As you probably already know, the NoSuchElementException is telling you the
> pool has been exhausted (and the "detail" message suggests you've got the
> pool configured to block for some finite amount of time before giving up).
> The most probable causes, in my experience:
> 
> 1. A peak in connection usage, causing the pool to be exhausted "naturally",
> (e.g,. you've capped the pool at 10 instances, and you suddenly need to use
> 11 at once).
> 
> 2. A slow leak, like Michael described:
> 
> > I suspect that you may have a pool leak.  Somewhere
> > you're borrowing from the pool and not returning it
> > to the pool.  Possibly the return of an object is
> > not in a finally block and an rare exception causes
> > it to lose one object.
> 
> If you can't tie the exception to activity in one way or another, then it's
> probably the latter.  Configurating the pool to "when exahausted, grow"
> would make the problem go away (at least as long as the database can support
> the traffic).  Setting the pool cap very low will make it happen more
> frequently, which may make it easier to diagnose and/or determine if the
> problem has been fixed.
> 
> Like Michael suggested, look for places where the connection.close() method
> isn't happenning in a finally block, and that the close call will always
> execute within that block.  (E.g., I sometimes see code like:
> 
> } finally {
>   resultset.close();
>   statement.close();
>   connection.close();
> }
> 
> which won't do what we want if either of the first two lines throws an
> Exception.  I use this idiom:
> 
> } finally {
>   try { resultset.close(); } catch(Exception e) { }
>   try { statement.close(); } catch(Exception e) { }
>   try { connection.close(); } catch(Exception e) { }
> }
> 
> and don't worry about null or anything else.)
> 

I have reviewed the customers JSP pages and found one page
where they were not wrapping their use of a db connection within a
try {} block.  I have informed them how to fix it.

But this one page does not explain running out of connections in a pool
with a max of 75 connections.  In the logs that page only failed twice
during the run of Tomcat before it ran out of db connections.

Thanks,

Glenn

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Glenn Nielsen             [EMAIL PROTECTED] | /* Spelin donut madder    |
MOREnet System Programming               |  * if iz ina coment.      |
Missouri Research and Education Network  |  */                       |
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