Setting Up Stackdriver Trace for C# ASP.NET

Stackdriver Trace can be enabled for ASP.NET Framework applications using the Google.Cloud.Diagnostics.AspNet client library for C#.

Installing the client library

To use the Google.Cloud.Diagnostics.AspNet client library in Visual Studio, do the following:

Right-click your solution in Visual Studio and select Manage Nuget packages for solution.
Select the Include prerelease checkbox.
Search for and install the package named Google.Cloud.Diagnostics.AspNet.

Configuring the client library

Once the Google.Cloud.Diagnostics.AspNet is installed, complete the following 3 steps to enable and configure trace:

Add the following XML element to the <appSettings> section your application's Web.config file and update YOUR-GOOGLE-PROJECT-ID to be your project ID or number:

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```
<add key="projectId" value="YOUR-GOOGLE-PROJECT-ID" />
```
Add the following using directive to your application's Global.asax.cs file:

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```
using Google.Cloud.Diagnostics.AspNet;
using Google.Cloud.Diagnostics.Common;
```
In the Global.asax.cs file's WebApiApplication class, add the following Init code block to initialize trace:

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```
public override void Init()
{
    string projectId = ConfigurationManager.AppSettings["projectId"];
    // ...
    base.Init();
    TraceConfiguration traceConfig = TraceConfiguration
        .Create(bufferOptions: BufferOptions.NoBuffer());
    CloudTrace.Initialize(this, projectId, traceConfig);
}
```
A sampling of the HTTP requests received by your application will now be traced automatically. You can also initiate traces from your application as demonstrated below in the sample application for ASP.NET Framework.

Running on Google Cloud Platform

The Google.Cloud.Diagnostics.AspNet client library should work without the need to manually provide authentication credentials for VM instances running on Google Cloud Platform, as long as the Stackdriver Trace API access scope is enabled on that instance.

App Engine

On Google App Engine flexible environment, the Stackdriver Trace API access scope is enabled by default, and the Google.Cloud.Diagnostics.AspNet client library can be used without needing to provide credentials or a project ID.

On Google App Engine standard environment, C# is not currently supported.

Container Engine

On Google Container Engine, add the trace.append OAuth access scope when creating the cluster:

gcloud container clusters create example-cluster-name --scopes https://www.googleapis.com/auth/trace.append

Compute Engine

For Google Compute Engine instances, you need to explicitly enable the trace.append Stackdriver Trace API access scope for each instance. When creating a new instance through the Google Cloud Platform Console, you can do this under Identity and API access: Use the Compute Engine default service account and select "Allow full access to all Cloud APIs" under Access scopes.

To use something other than the Compute Engine default service account see the docs for Creating and Enabling Service Accounts for Instances and the Running elsewhere section below. The important thing is that the service account you use has the Cloud Trace Agent role.

Running locally and elsewhere

If your application is running outside of Google Cloud Platform, such as locally, on-premise, or on another cloud provider, you can still use Stackdriver Trace, provided that you supply a project ID and credentials to the Google.Cloud.Diagnostics.AspNet client library.

Project ID

Provide a project ID to the Google.Cloud.Diagnostics.AspNet client library by entering your project ID into the Web.config file as described above in step #1 of the Configuring the client library section.

Credentials

Google Cloud Platform client libraries use a strategy called Application Default Credentials (ADC) to find your application's credentials. You can provide credentials to the Google.Cloud.Diagnostics.AspNet client library by setting the GOOGLE_APPLICATION_CREDENTIALS environment variable:

Linux or Mac OS X

    export GOOGLE_APPLICATION_CREDENTIALS=path-to-private-key-for-your-service-account

Windows

    set GOOGLE_APPLICATION_CREDENTIALS=path-to-private-key-for-your-service-account

Powershell:

    $env:GOOGLE_APPLICATION_CREDENTIALS="path-to-private-key-for-your-service-account"

For more information, see Providing credentials to your application.

Sample Stackdriver Trace application for ASP.NET Framework

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public class TraceController : Controller
{
    // This incoming HTTP request should be captured by Trace.
    public ActionResult Index()
    {
        using (CloudTrace.Tracer.StartSpan(nameof(Index)))
        {
            string url = "https://www.googleapis.com/discovery/v1/apis";
            var response = TraceOutgoing(url);
            ViewData["text"] = response.Result.ToString();
            return View();
        }
    }

    public async Task<string> TraceOutgoing(string url)
    {
        // Manually trace a specific operation.
        using (CloudTrace.Tracer.StartSpan("get-api-discovery-doc"))
        {
            using (var httpClient = new HttpClient())
            {
                // This outgoing HTTP request should be captured by Trace.
                using (var response = await httpClient.GetAsync(url)
                    .ConfigureAwait(false))
                {
                    return await response.Content.ReadAsStringAsync();
                }
            }
        }
    }
}

Viewing the traces

After deployment, you can view the traces in the Cloud Platform Console Trace Viewer.

Go to the Trace Viewer page