[a little OT] mod_proxy 502 errors in dual apache setup

[John ORourke <suppressed>]

Hi folks,

Slightly OT but hopefully someone on here has had similar experience.  
I've got a site with fairly heavy traffic and a light/heavy apache 
setup.  Occasionally the back-end servers seem to get swamped and 
suddenly every request from the front end starts getting a 502 proxy 
timeout until I restart both apache servers.

I'm about to start digging through logs to try and track down the issue 
but wondered if anyone who's seen this before could give me a head start.

cheers
John