Custom Span Tagging w/ Middleware - aspnetcore 2.1 about dd-trace-dotnet

[lucaspimentel]

Glad you got it sorted out, @scottzilla!

[scottzilla]

Here is the correct Startup.cs:

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    else
    {
        app.UseHsts();
    }

    app.UseDataDogTracing("myCoolService");
    app.UseMvc();
}

This is rather obvious in retrospect: the original example lets the MVC middleware short-circuit and handle the response (as it should), and the DataDog middleware never gets hit as part of the request lifecycle.

(The false positives I was seeing were actually 404s as I was hitting the wrong endpoint, and therefore Mvc middleware would not handle the request, and then the DataDog middleware would be executed.)