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From Jeremy Wall <jer...@marzhillstudios.com>
Subject Re: Apache2.2 - openssl 0.9.8d - modperl 2.03 unpredictable timeouts during requests
Date Mon, 05 Mar 2007 21:20:23 GMT
On Monday 05 March 2007 15:08, Jonathan Vanasco wrote:
> On Mar 5, 2007, at 3:40 PM, Perrin Harkins wrote:
> > Look for things that use locking.  Anything that updates a file or a
> > database row.  In particular, look for things that do this and would
> > happen on every type of request that you've seen hanging so far.
>
> As a note, you could run into blocks/locks/stalls from foreign keys.
>
> I recently had this code in my system
>
> 	handle 1- 	select * from account where id = 1;
> 	handle 2- 	update visit set visit_count= visit_count+1 where
> account_id = 1;	# account_id fkeys on account
>
> it took me forever to realize why my system kept locking.  the select
> + transaction on handle 1 was getting an exclusive lock, and the
> update was queued , trying to do an internal select on the fkey for
> integrity checks
>
> the moral: db lock problems can happen where you least expect them
>

There is an update that occurs to the session management tables everytime a 
request is made when the user is logged in. I'll take a look at those updates 
maybe something is going on there. Thanks for the insights guys you've been 
very helpful.

>
> // Jonathan Vanasco
>

Jeremy Wall

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