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Resource SDK

A Resource is an immutable representation of the entity producing telemetry. For example, a process producing telemetry that is running in a container on Kubernetes has a Pod name, it is in a namespace and possibly is part of a Deployment which also has a name. All three of these attributes can be included in the Resource.

The primary purpose of resources as a first-class concept in the SDK is decoupling of discovery of resource information from exporters. This allows for independent development and easy customization for users that need to integrate with closed source environments. The SDK MUST allow for creation of Resources and for associating them with telemetry.

When used with distributed tracing, a resource can be associated with the TracerProvider when it is created. That association cannot be changed later. When associated with a TracerProvider, all Spans produced by any Tracer from the provider MUST be associated with this Resource.

Analogous to distributed tracing, when used with metrics, a resource can be associated with a MeterProvider. When associated with a MeterProvider, all metrics produced by any Meter from the provider will be associated with this Resource.

Resource creation

The SDK must support two ways to instantiate new resources. Those are:

Create

The interface MUST provide a way to create a new resource, from Attributes. Examples include a factory method or a constructor for a resource object. A factory method is recommended to enable support for cached objects.

Required parameters:

Merge

The interface MUST provide a way for a primary resource and a secondary resource to be merged into a new resource.

Note: This is intended to be utilized for merging of resources whose attributes come from different sources, such as environment variables, or metadata extracted from the host or container.

The resulting resource MUST have all attributes that are on any of the two input resources. Conflicts (i.e. a key for which attributes exist on both the primary and secondary resource) MUST be handled as follows:

  • If the value on the primary resource is an empty string, the result has the value of the secondary resource.
  • Otherwise, the value of the primary resource is used.

Attribute key namespacing SHOULD be used to prevent collisions across different resource detection steps.

Required parameters:

  • the primary resource whose attributes take precedence.
  • the secondary resource whose attributes will be merged in.

The empty resource

It is recommended, but not required, to provide a way to quickly create an empty resource.

Note that the OpenTelemetry project documents certain "standard attributes" that have prescribed semantic meanings.

Resource operations

Resources are immutable. Thus, in addition to resource creation, only the following operations should be provided:

Retrieve attributes

The SDK should provide a way to retrieve a read only collection of attributes associated with a resource. The attributes should consist of the name and values, both of which should be strings.

There is no need to guarantee the order of the attributes.

The most common operation when retrieving attributes is to enumerate over them. As such, it is recommended to optimize the resulting collection for fast enumeration over other considerations such as a way to quickly retrieve a value for a attribute with a specific key.