title: Signal Bus error (7)
body: <p>For a number of months now one of our client sites has been suffering Signal Bus Error (7) issues; as a heavy traffic site, the error has been known to be seen 100s of times a day.</p>
  
  <p>On the front-end of the site, it shows up a 502 Gateway Error, primarily as we have Nginx running in tandem with Apache. </p>
  
  <p>Our hosting provider has checked the server hardware and carried out a re-install of Apache, but the issues continue.</p>
  
  <p>When the site was suspended; the errors stopped; bringing that site out of maintenance meant the errors popping up again.</p>
  
  <p>Based on experience does this mean that this is a site code level issue and if so what is the recommended way to source the issue on a Magento site? Or could this be related to something like APC?</p>
  
  <p>For reference we are running a Centos 5.8 server, with 16 CPU Cores and 32GB memory. We are running PHP 5.3.18 with Ion Cube Loader &amp; Zend Engine. The site on the server is also using APC.</p>
  
  <p>Any thoughts would be greatly appreciated; happy to provide more information.</p>