Error: Server cannot append header after HTTP headers have been sent

[VanHelSeenG]

After some tests with turned on GZip compression I found what CompressionHandler generate this exception. An exception occurs most often during server get unauthorized requests and sometimes during authorized.I use ordinary OWIN OAuth. Exception also occurs when I send request to auth /token endpoint. I attached screenshot of stack trace(begin of it). Please, help with problem

[azzlack]

This is related to OWIN: http://katanaproject.codeplex.com/discussions/540202

According to them, it is fixed in .NET 4.6, but I will see if I can find a workaround for this version.

[fr4nky80]

solution for this?

[pranaydutta89]

👍

[pcoulter]

(bump)

[azzlack]

So. This will be solved by downloading an extra package that contains a special OwinServerCompressionHandler. This is a separate package because the base package does not require Owin.

[HughJeffner]

I have a somewhat strange setup using Owin + Identity + CookieAuthenticationMiddleware and the OwinServerCompressionHandler fails to detect the headers have already been sent. I use AuthenticationManager.SignIn and AuthenticationManager.SignOut methods in my controller and this is what ultimately modifies the headers by inserting some cookies into the response. The exception is thrown on a background thread and the set-cookie headers never make it into the response.

The current workaround is to disable compression for these methods which isn't a big deal. It just took many hours of detective work to figure out this module was the cause 🔍 😦