IIS7 Application Request Routing (arr reverse proxy) combined with managed module - time out

Question

I am trying to build a proxy that would serve requests to an internal site (hiding the origin) but at the same time inspect the packets and asynchronously post-process them.

Answer 1

I just ran into this bug and your experiences helped me determine the root cause.

My main server is MVC based and it looks at the Request.Form values in the Application_BeginRequest method. If the form values are accessed ARR fails to forward the body of a HTTP POST request. GET requests will work fine since there is no body.

I have routes.IgnoreRoute ("Forum/{*pathInfo}"); as a registered route but ARR runs as a HttpModule and doesn't kick-in until later in the pipeline. That means my MVC based application is given the opportunity to access the content of the POST body which somehow prevents ARR from accessing the body itself and forwarding it to the proxy'd server.

Here is Cosmin's related post on the iis.net forums: ARR 2.0 BUG - combined with managed http module timeout on read inputstream

In my application I have all myserver.com/Forum/* requests being reverse proxy'd to a separate application on another server. So I simply checked the HttpContext.Current.Request.Url in my MVC application's Application_BeginRequest method to make sure it does not contain /Forum before accessing the Request.Form values. Once I did that the POST bodies made it through ARR just fine.

UPDATE: after further testing it appears that there are still problems with ARR as POST from non-authenticated users still fails. Instead of the main website being MVC I created a dummy IIS .NET 4.0 website with a single Default.html document. But I still ran into problems with POST requests and ARR. Then I switch the application pool to ASP.NET 2.0 and what do you know, it works. At this point I have to assume that something in the .NET 4.0 pipeline is accessing the input stream which prevents ARR from accessing the input stream itself in order to forward the POST body.