Tuesday, July 18, 2006
Inherit With Care
I was asked to look at an ASP.NET 1.1 application that was designed with a distributed architecture using .NET Remoting. Over a period of a few hours of heavy usage, this production application would intermittently bring the Windows 2003 Server that it was being hosted on to a screeching halt. Cause unknown. No event log entries, nothing suspicious in IIS logs, nothing too special about the application that would indicate this behavior. Performance monitoring, however, indicated that the handles on the OS would gradually increase to dangerous levels of 50,000+ before the application would crash. Hmmm, what could be using so many handles and not releasing them? My first instinct was to make sure that all the remoting objects were disposed properly after use. Upon closer investigation, however, I found out that all ASP.NET pages in the application were inheriting from a custom base class. The base class was overriding the page's Init method, and guess what I found in that method? A call to RemotingConfiguration.Configure() method. At first I was surprised why would someone configure remoting every single time a page is instantiated? Soon it hit me why system handles were astronomically increasing. Once that line of code was moved to Application_Start event, the application hasn't crashed in weeks. Moral of the story? Inheritance is a good OO concept, but only we as developers can decide how badly we want to abuse it!