# Resources {{__hugo_ctx pid=354}} A [resource](/docs/concepts/resources/) represents the entity producing telemetry as resource attributes. For example, an OTP Release producing telemetry that is running in a container on Kubernetes has an OTP Release 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. {{__hugo_ctx/}} ## Using resource detectors Resource detectors fetch resource attributes from various sources. The default detectors use the OS environment variable `OTEL_RESOURCE_ATTRIBUTES` and the `opentelemetry` OTP application environment variable `resource`. The detectors to use is a list of module names and can be configured in the Application configuration:

%% sys.config
{opentelemetry, {resource_detectors, [otel_resource_env_var, otel_resource_app_env]}}

## runtime.exs
config :opentelemetry, resource_detectors: [:otel_resource_env_var, :otel_resource_app_env]

Or through the environment variable `OTEL_RESOURCE_DETECTORS`: ```sh OTEL_RESOURCE_DETECTORS=otel_resource_env_var,otel_resource_app_env ``` All resources detectors are protected with a timeout, in milliseconds, after which they return an empty value. This allows for resource detectors to do things like hit the network without potentially hanging the entire program indefinitely. The default is 5000 milliseconds and can be set with environment variable `OTEL_RESOURCE_DETECTOR_TIMEOUT` or Application variable `otel_resource_detector_timeout`. ## Adding resources with OS and OTP application environment variables With the two default resource detectors enabled you can set resource attributes either with the OS environment variable `OTEL_RESOURCE_ATTRIBUTES`: ```sh OTEL_RESOURCE_ATTRIBUTES="deployment.environment=development" ``` Alternatively, use the `resource` OTP application environment under the `opentelemetry` Application configuration of `sys.config` or `runtime.exs`:

%% sys.config
{opentelemetry, {resource, #{deployment => #{environment => <<"development">>}}}}

## runtime.exs
config :opentelemetry, resource: %{deployment: %{environment: "development" }}

Resource attributes in the `resource` OTP application environment variable are flattened and combined with `.`, so `#{deployment => #{environment => <<"development">> }` is the same as `#{'deployment.environment' => <<"development">>}`. ## Custom resource detectors Custom resource detectors can be created by implementing the [`otel_resource_detector` behaviour](https://hexdocs.pm/opentelemetry/1.3.0/otel_resource_detector.html#callbacks) which contains a single callback `get_resource/1` that returns an [`otel_resource`](https://hexdocs.pm/opentelemetry/1.3.0/otel_resource.html). Note that there are [semantic conventions](/docs/specs/semconv/resource/) defined for `resource` that should be followed if they apply when adding new resource attributes.