What starts first Application_Start or WebRole's OnStart?

Question

I have MVC project on Windows Azure. This project has WebRole with method OnStart. And I want to know what starts first Application_Start of Global.asax or WebRole's OnStart?

Answer 1

Pretty sure this is non-deteministic after SDK 1.3. Trying to time something from one to the other will just end in a race condition.

Prior to 1.3, the Hosted Worker Core (HWC) was hosted in the RoleEntryPoint, so there was a deterministic startup (OnStart, Application_OnStart, IIRC). However, with IIS hosting the web now, it is the IISConfigurator.exe that creates the app pool, etc, and eventually w3wp.exe hosts your web site. This is a different process than your RoleEntryPoint, so either one could start first.

Answer 2

I can't find any 100% complete references on this (about the best I've seen is http://blog.syntaxc4.net/?p=271), but I believe the sequence is:

• Any startup tasks are run
• WebRole OnStart method is called
• The WebRole Run() method is called - and at the same time IIS starts the websites - so at this point Application_Start will get called for the first time.