Drupal WSOD (White Screen of Death) - simple fix

 The Drupal WSOD (White Screen of Death) is a scary problem, especially due to the lack of information typically associated with it's occurrence. I've seen it manifest itself in a simple way, which doesn't seem to be linked to any particular user or administrator action. All of a sudden, a visit to your site results in nothing but a blank white screen; no web browser errors, no content, no nothing, just a blank white screen. This is a problem unique to Drupal, but non-the-less frustrating. If you are reading this now, you're on our site which is based on Drupal.

I've seen a few not-so-well described errors from MySQL in the event log, I'm not too fond of troubleshooting PHP, and this appears to be an operational error (not associated with any changes). I also find that I can get to any page but the home page (no url path), which is just an alias of a specific node or just '/<front>'. I tried logging in and clearing cache, updating database, entering/exiting maintenance mode, etc, and nothing worked. Then I rebooted the server, still no love. So then, after the server was up, I manually restarted the MySQL service. This seemed to do the trick. As I have more time to dig into the root causes, I'll update this post.

Also, a few tidbits about our architecture:

• The entire stack runs on each web server, which consists of:
  • Drupal 6
  • MySQL 5
  • PHP 5
  • Microsoft IIS 7.5
  • Microsoft Server 2008 R2
• There are three (3) redundant (N+2) servers which are geographically distributed, and utilize DNS for failover and load balancing mechanism
• The sites are protected in reverse proxy by Microsoft TMG 2010 clusters
• Content is replicated using Microsoft's FRS technology
• Databases are replicated via a master-slave relationship, more on making that work in the MySQL KB