Resources in OpenTelemetry .NET

A resource represents the entity producing telemetry as resource attributes. For example, a process producing telemetry that is running in a container on Kubernetes has a process name, a pod name, a namespace, and possibly a deployment name. All four of these attributes can be included in the resource.

In your observability backend, you can use resource information to better investigate interesting behavior. For example, if your trace or metrics data indicate latency in your system, you can narrow it down to a specific container, pod, or Kubernetes deployment.

What are resources?

In OpenTelemetry, a resource is an immutable representation of the entity producing telemetry. For example, a resource could represent a Kubernetes container, a Linux or Windows process, or an application running within a process.

Resources are a fundamental concept in OpenTelemetry, and they are used to describe the source of telemetry data. This information is valuable for debugging and analyzing telemetry data.

Resource attributes

Resource attributes are key-value pairs that provide metadata about the resource. OpenTelemetry defines a set of semantic conventions for resource attributes, which should be used when applicable.

Common resource attributes include:

• service.name: The name of the service generating telemetry
• service.version: The version of the service
• service.namespace: A namespace for the service
• service.instance.id: A unique identifier for the service instance
• host.name: The name of the host
• deployment.environment: The deployment environment (e.g., production, staging)

Setup

Follow the instructions in the Getting Started, so that you have a running .NET app exporting data to the console.

Adding resources with environment variables

You can use the OTEL_RESOURCE_ATTRIBUTES environment variable to inject resources into your application. The .NET SDK will automatically detect these resources.

The following example adds Service, Host and OS resource attributes via environment variables, running unix programs like uname to generate the resource data.

$ env OTEL_RESOURCE_ATTRIBUTES="service.name=resource-tutorial-dotnet,service.namespace=tutorial,service.version=1.0,service.instance.id=`uuidgen`,host.name=`HOSTNAME`,host.type=`uname -m`,os.name=`uname -s`,os.version=`uname -r`" dotnet run  Activity.TraceId: d1cbb7787440cc95b325835cb2ff8018 Activity.SpanId: 2ca007300fcb3068 Activity.TraceFlags: Recorded Activity.ActivitySourceName: tutorial-dotnet Activity.DisplayName: SayHello Activity.Kind: Internal Activity.StartTime: 2022-10-02T13:31:12.0175090Z Activity.Duration: 00:00:00.0003920 Activity.Tags:  foo: 1  bar: Hello, World!  baz: [1,2,3] Resource associated with Activity:  service.name: resource-tutorial-dotnet  service.namespace: tutorial  service.version: 1.0  service.instance.id: 93B14BAD-813D-48EE-9FB1-2ADFD07C5E78  host.name: myhost  host.type: arm64  os.name: Darwin  os.version: 21.6.0 

Adding resources in code

You can also add custom resources in code by attaching them to a ResourceBuilder.

The following example builds on the getting started sample and adds two custom resources, environment.name and team.name in code:

using System.Diagnostics; using System.Collections.Generic;  using OpenTelemetry; using OpenTelemetry.Trace; using OpenTelemetry.Resources;  var serviceName = "resource-tutorial-dotnet"; var serviceVersion = "1.0";  var resourceBuilder =  ResourceBuilder  .CreateDefault()  .AddService(serviceName: serviceName, serviceVersion: serviceVersion)  .AddAttributes(new Dictionary<string, object>  {  ["environment.name"] = "production",  ["team.name"] = "backend"  });  var sourceName = "tutorial-dotnet";  using var tracerProvider = Sdk.CreateTracerProviderBuilder()  .AddSource(sourceName)  .SetResourceBuilder(resourceBuilder)  .AddConsoleExporter()  .Build();  var MyActivitySource = new ActivitySource(sourceName);  using var activity = MyActivitySource.StartActivity("SayHello"); activity?.SetTag("foo", 1); activity?.SetTag("bar", "Hello, World!"); activity?.SetTag("baz", new int[] { 1, 2, 3 }); 

In this example, the service.name and service.version values are set in code as well. Additionally, service.instance.id gets a default value.

If you run the same command as in Adding resources with environment variables, but this time without service.name service.version, and service.instance.id, you’ll see the environment.name and team.name resources in the resource list:

$ env OTEL_RESOURCE_ATTRIBUTES="service.namespace=tutorial,host.name=`HOSTNAME`,host.type=`uname -m`,os.name=`uname -s`,os.version=`uname -r`" dotnet run  Activity.TraceId: d1cbb7787440cc95b325835cb2ff8018 Activity.SpanId: 2ca007300fcb3068 Activity.TraceFlags: Recorded Activity.ActivitySourceName: tutorial-dotnet Activity.DisplayName: SayHello Activity.Kind: Internal Activity.StartTime: 2022-10-02T13:31:12.0175090Z Activity.Duration: 00:00:00.0003920 Activity.Tags:  foo: 1  bar: Hello, World!  baz: [1,2,3] Resource associated with Activity:  environment.name: production  team.name: backend  service.name: resource-tutorial-dotnet  service.namespace: tutorial  service.version: 1.0  service.instance.id: 28976A1C-BF02-43CA-BAE0-6E0564431462  host.name: pcarter  host.type: arm64  os.name: Darwin  os.version: 21.6.0 

Note: If you set resource attributes with both environment variables and code, the values in code take precedence.

Next steps

There are more resource detectors you can add to your configuration, for example to get details about your Cloud environment or Deployment.

Learn more

For more information about resources in OpenTelemetry, see the Resources SDK specification.