HAProxy out the ears

Insomnia? Try this:
http://haproxy.1wt.eu/download/1.5/doc/configuration.txt

When you get 503's with "sH" in your HAProxy Logs, maybe its time to make sure your service actually responds in a reasonable time frame.

sH   The "timeout server" struck before the server could return its
          response headers. This is the most common anomaly, indicating too
          long transactions, probably caused by server or database saturation.
          The immediate workaround consists in increasing the "timeout server"
          setting, but it is important to keep in mind that the user experience
          will suffer from these long response times. The only long term
          solution is to fix the application.