No RouteData when using custom exception handler

We have a problem with prometheus-net reporting empty controller and action labels when the exception occurs:

http_request_duration_seconds_count{code="500",method="GET",controller="",action=""}
...

We do have a custom exception handler set up:

app.UseHttpMetrics();
app.UseMetricServer();
// ....
app.UseExceptionHandler(errorApp =>
{
    errorApp.UseMiddleware<ExceptionHandlerMiddleware>();	
});

The root of the problem seems to be in these lines in the ExceptionHandlerMiddleware class:

// An endpoint may have already been set. Since we're going to re-invoke the middleware pipeline we need to reset
// the endpoint and route values to ensure things are re-calculated.
context.SetEndpoint(endpoint: null);
var routeValuesFeature = context.Features.Get<IRouteValuesFeature>();
routeValuesFeature?.RouteValues?.Clear();

I presume that this change was made based on this issue and made it to ASP.NET Core 3.0 that we use.

Is there a workaround? Can it probably be fixed via different order of middleware registrations?

[sandersaares]

Updated preview build of v3.4.0 is uploading now. Just call UseHttpMetrics after UseRouting and it will persist the route data. Any later changes to route data (e.g. in exception handlers) will not affect metrics.

Edit: Now published as stable. Eager to hear your feedback!

Please let me know if this appears to solve your problem.

[ivonin]

Yes, everything works fine, thanks!

The problem with error codes as due to incorrect order of middleware registrations.