I have a Wordpress+Buddypress installation which is regularly going down - the number of HTTPD on the server and the server CPU load both peak suddenly and the server fails to recover. A restart of the web service is required.
I'm looking for troubleshooting advice.
Edit: Moved from the comment in here to make the goal clear.
I'm not getting any useful information out of the error log, even when enabling debug mode in Wordpress. I have tidied up a lot of sloppy code in plugins and themes which were throwing PHP notices, to no effect.
I have defined ERRORLOGFILE to log MU errors, but nothing has been logged there as yet. I have tried using Debug Bar for Wordpress with SQL logging enabled, but this has not shown anything useful - as far as I can see it does not log db transactions to file, and the Debug Bar only shows db queries for one site at a time. We have over 3000 sites running in this installation.
Other information: we are using WP Super Cache, using mod_rewrite. I have noticed quite a few errors in the error log to do with Wordpress trying to add or remove cache files which don't exist. I don't know if this is normal, or relevant.
Wordpress and Buddypress are the most recent versions as of writing: 3.5.1 / 1.6.4
I am looking for more tips in pinpointing the cause of the issue. I have started gradually disabling recently activated plugins, but this is not going to be practical for all plugins on the live site.
Any ideas? Thanks.