Owin–Stage Markers

While reviewing some code I noticed the following code snippet;

	public void Configuration(IAppBuilder app)
	{
	//Removed other code
	app.UseStageMarker(PipelineStage.ResolveCache);
	}

view raw Startup.cs hosted with ❤ by GitHub

I had no clue what Stage Markers where so time to dig in…

What are stage markers?

Stage markers play a rol when you are using OWIN in IIS. IIS has a specific execution pipeline containing a predefined set of pipeline events. If you want to run a specific set of OWIN middleware  during a particular stage in the IIS pipeline, you  can use the UseStageMarker method as seen in the sample above.

Stage marker rules

There are rules on which stage of the pipeline you can execute middleware and the order components must run. Following stage events are supported:

	public enum PipelineStage
	{
	Authenticate = 0,
	PostAuthenticate = 1,
	Authorize = 2,
	PostAuthorize = 3,
	ResolveCache = 4,
	PostResolveCache = 5,
	MapHandler = 6,
	PostMapHandler = 7,
	AcquireState = 8,
	PostAcquireState = 9,
	PreHandlerExecute = 10,
	}

view raw PipelineStage.cs hosted with ❤ by GitHub

By default, OWIN middleware runs at the last event (PreHandlerExecute). To run a set of middleware components during an earlier stage, insert a stage marker right after the last component in the set during registration.

	public void Configuration(IAppBuilder app)
	{
	//This middleware will run at the ResolveCache event in the IIS pipeline
	app.Use((context, next) =>
	{
	return next.Invoke();
	});
	app.UseStageMarker(PipelineStage.ResolveCache);
	//This middleware will run at the PreRequestExecute event in the IIS pipeline
	app.Use((context, next) =>
	{
	return next.Invoke();
	});
	}

view raw StageMarker.cs hosted with ❤ by GitHub

More information: https://docs.microsoft.com/en-us/aspnet/aspnet/overview/owin-and-katana/owin-middleware-in-the-iis-integrated-pipeline