facebook/tornado — pull request #616 by psobot (2012-10-23 18:34:31+00:00)
Title: Added period check in PeriodicCallback

If a user currently passes in 0ms (hopefully by accident) as the callback time for a periodic callback, Tornado consumes a huge amount of CPU and never calls the function. Ideally, this should raise an exception in its constructor to ensure the value makes sense. (Alternatively, a callback time of 0 could mean "call this function on every single IOLoop tick," but I haven't implemented that here.)