Seamless deployment in ASP.NET (IIS kills worker process before new worker process is ready)

Question

I am trying to deploy a .NET Web application to IIS (7.5) without any hassle for the users. I have made sure that Disable Overlapped Recycle is False but i still run into the same problem every time.

Every time I upload new binaries for the site, IIS kills the worker process before it has started a new one. So every time I upload new binaries users get this error message:

Server Error in '/' Application. Could not load file or assembly 'MyApplicationWeb' or one of its dependencies. The process cannot access the file because it is being used by another process. (Exception from HRESULT: 0x80070020)

I have no idea how to do this seamless. As it is now I just upload the binary; but while the upload occurs (or local copy) it will give the above quoted behaviour. I also tried using a Web garden but with same result.

What I am not looking for:

• How to solve it with external load balancers (it's a functional solution but it is perfomance wise a bad solution for few servers and it won't work at all if there's only one server)
• How to create a hack-around with a refresh in a custom error page (as it has some obvious problems but more importantly wont work at all with web services/ajax).

I really think this should be doable given http://www.microsoft.com/technet/prodtechnol/WindowsServer2003/Library/IIS/24e3c22e-79a9-4f07-a407-dbd0e7f35432.mspx?mfr=true

Update: In article above they say:

However, because the shutdown timeout value of a shutdown or startup is configurable, the worker process can be terminated while it is still serving requests if it does not finish servicing existing requests within the time limit.

I have no idea where to find this value nor what it's default. If its less then a few second it might explain my results.

ps. I am posting it on SO rather than on SF/Webmasters etc because I think this kind of knowledge will probably be minimal amongst people who aren't active in development, I hope this is all right.

Answer 1

When deploying ASP.Net applications I create a new folder on the server and change the home directory of the website within IIS. This provides zero downtime deployment and a quick rollback position in case of unforeseen issues. On a future update I scrap the old version and repeat the process so that there is always a single rollback position.

Update - Shutdown time limit

Details configuring the shutdown time limit for workers is detailed at http://www.iis.net/ConfigReference/system.applicationHost/applicationPools/add/processModel. The default is 1 min 30 secs. Look for the shutdownTimeLimit section in the linked page.

Update - More information

Similar question with a great answer

The gist of this is that the due to overwritting the existing files the copying mechanism takes an exclusive lock on the files and that it is not possible to have seemless deployment without use of app_offline.htm or a mechanism such as suggested above. Take a read of the linked answer as it goes into much more depth.