Middleware not invoked for synchronous requests

Question

I try to log unhandled exceptions to sentry using SentryDotNet.AspNetCore.

My startup.cs has

   public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc();

        var dsn = "[dsn]";


        services.AddSentryDotNet(
            new SentryClient(
                dsn,
                new SentryEventDefaults(
                    environment: "test",
                    release: typeof(Startup).Assembly.GetName().Version.ToString(3),
                    logger: "coremvcapp")));
    }

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {

        app.UseStaticFiles();

        app.UseMvc(routes =>
        {
            routes.MapRoute(
                name: "default",
                template: "{controller=Home}/{action=Index}/{id?}");
        });

        app.UseSentryDotNet(new SentryDotNetOptions { CaptureRequestBody = true });
 //app.Run(async context => { await DoSomethingAsync(context); });
    }

There is a sample call to invoke the middleware which logs successfully to sentry.

private static async Task DoSomethingAsync(HttpContext context)
{
    if (context.Request.Path.HasValue && context.Request.Path.Value.Contains("error"))
    {
        throw new InvalidOperationException("Boom");
    }
    await context.Response.WriteAsync("some stuff");
}

The problem is that if an exception is thrown in a controller action the middleware is not invoked.

    public IActionResult LogError()
    {
        throw new Exception("mvc error");
    }

I set a breakpoint to the Invoke method of the middleware and it is not hit when the exception in the action is thrown.

The middleware has this Invoke method

    public async Task Invoke(HttpContext context)
    {
        try
        {
            await _next.Invoke(context);
        }
        catch (Exception e) when (_client != null)
        {
            // log stuff

            throw;
        }
    }

I see that it gets initialized when the application starts

public SentryDotNetMiddleware(RequestDelegate next, ISentryClient client, SentryDotNetOptions options)
{
    _next = next;
    _client = client;
    _options = options;

}

Is there something missing so that the invoke method of the middleware gets called for the unhandled excetion in the action?

Edit

For me the implementation as provided by sentry Sentry.AspNetCore worked out of the box. There were other little glitches with all the other packages I tried.

Answer 1

The order you add middleware is important as they are invoked in the order they were added to the pipeline.

Loggers and error handlers should be added very early to the pipeline.

Make sure you UseSentryDotNet() after any middleware that intercepts exceptions. Otherwise, the SentryDotNet middleware will not see the exception. E.g. the app.UseDeveloperExceptionPage() should be used before app.UseSentryDotNet()

Reference GitHub : SentryDotNet

public void Configure(IApplicationBuilder app, IHostingEnvironment env) {
    // Make sure middleware that catches exceptions without 
    // rethrowing them is added *before* SentryDotNet
    app.UseDeveloperExceptionPage();

    //Add sentry
    app.UseSentryDotNet(new SentryDotNetOptions { CaptureRequestBody = true });

    // Other middleware, e.g. app.UseMvc()

    app.UseStaticFiles();

    app.UseMvc(routes =>
    {
        routes.MapRoute(
            name: "default",
            template: "{controller=Home}/{action=Index}/{id?}");
    });
}

The reason your example worked is because you added it after having added the sentry middleware.

In the other calls the errors are occurring before it reaches the sentry middleware so they are not going to be caught.

Reference ASP.NET Core Middleware

Reference Handle errors in ASP.NET Core