# Resources in OpenTelemetry .NET

> Learn about resources and how to use them in OpenTelemetry .NET

---


A [resource](/docs/concepts/resources/) 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.
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## 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](/docs/specs/semconv/resource/) 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.

```console
$ 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:

```csharp
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](#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:

```console
$ 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][].

[getting started]: /docs/languages/dotnet/getting-started/
[host]: /docs/specs/semconv/resource/host/
[cloud]: /docs/specs/semconv/resource/cloud/
[deployment]: /docs/specs/semconv/resource/deployment-environment/
[service]: /docs/specs/semconv/resource/#service
[os]: /docs/specs/semconv/resource/os/

## Learn more

For more information about resources in OpenTelemetry, see the
[Resources SDK specification](/docs/specs/otel/resource/sdk/).