OWIN Instrumentation for OpenTelemetry .NET

This is an Instrumentation Library, which instruments OWIN/Katana and collects telemetry about incoming requests.

Steps to enable OpenTelemetry.Instrumentation.Owin

An example project is available in the examples/owin folder.

Step 1: Install Package

Add a reference to the OpenTelemetry.Instrumentation.Owin package. Also, add any other instrumentations & exporters you will need.

dotnet add package OpenTelemetry.Instrumentation.Owin

Step 2: Configure OWIN middleware

Call the UseOpenTelemetry IAppBuilder extension to register OpenTelemetry middleware which emits diagnostic events from th OWIN pipeline. This should be done before any other middleware registrations.

    using var host = WebApp.Start(
        "http://localhost:9000",
        appBuilder =>
        {
            appBuilder.UseOpenTelemetry();
        });

Step 3: Enable OWIN Instrumentation at application startup

Configure OpenTelemetry TracerProvider

Call the AddOwinInstrumentation TracerProviderBuilder extension to register OpenTelemetry instrumentation which listens to the OWIN diagnostic events.

    using var openTelemetry = Sdk.CreateTracerProviderBuilder()
        .SetResourceBuilder(ResourceBuilder.CreateDefault().AddService("Owin-Example"))
        .AddOwinInstrumentation()
        .AddConsoleExporter()
        .Build();

Following list of attributes are added by default on activity. See http-spans for more details about each individual attribute:

• http.request.method
• http.request.method_original
• http.response.status_code
• network.protocol.version
• user_agent.original
• server.address
• server.port
• url.path
• url.query - By default, the values in the query component are replaced with the text Redacted. For example, ?key1=value1&key2=value2 becomes ?key1=Redacted&key2=Redacted. You can disable this redaction by setting the environment variable OTEL_DOTNET_EXPERIMENTAL_OWIN_DISABLE_URL_QUERY_REDACTION to true.
• url.scheme

Configure OpenTelemetry MeterProvider

Call the AddOwinInstrumentation MeterProviderBuilder extension to register OpenTelemetry instrumentation which generates request duration metrics for OWIN requests.

The metric implemention does not rely on tracing, and will generate metrics even if tracing is disabled.

    using var openTelemetry = Sdk.CreateMeterProviderBuilder()
        .SetResourceBuilder(ResourceBuilder.CreateDefault().AddService("Owin-Example"))
        .AddOwinInstrumentation()
        .AddConsoleExporter()
        .Build();

The instrumentation is implemented based on metrics semantic conventions. Currently, the instrumentation supports the following metric.

Customize OWIN span names

The OpenTelemetry OWIN instrumentation will create spans with very generic names based on the http method of the request. For example: HTTP GET or HTTP POST. The reason for this is the OpenTelemetry Specification http semantic conventions call specifically for low cardinality values and OWIN does not expose any kind of route template.

To change the span name set Activity.Current.DisplayName to the value you want to display once a route has been resolved. Here is how this can be done using WebAPI:

    using var host = WebApp.Start(
        "http://localhost:9000",
        appBuilder =>
        {
            appBuilder.UseOpenTelemetry();

            HttpConfiguration config = new HttpConfiguration();

            config.MessageHandlers.Add(new ActivityDisplayNameRouteEnrichingHandler());

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional });

            appBuilder.UseWebApi(config);
        });

    private class ActivityDisplayNameRouteEnrichingHandler : DelegatingHandler
    {
        protected override async Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken)
        {
            try
            {
                return await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
            }
            finally
            {
                var activity = Activity.Current;
                if (activity != null)
                {
                    var routeData = request.GetRouteData();
                    if (routeData != null)
                    {
                        activity.DisplayName = routeData.Route.RouteTemplate;
                    }
                }
            }
        }
    }

References

• Open Web Interface for .NET
• Katana Project
• OpenTelemetry Project