Function as a Service

Status: Experimental

type: faas

Description: A “function as a service” aka “serverless function” instance.

See also:

• The Trace semantic conventions for FaaS
• The Cloud resource conventions

FaaS resource attributes

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.name	string	The name of the single function that this runtime instance executes. [1]	my-function; myazurefunctionapp/some-function-name	Required
cloud.resource_id	string	Cloud provider-specific native identifier of the monitored cloud resource (e.g. an ARN on AWS, a fully qualified resource ID on Azure, a full resource name on GCP) [2]	arn:aws:lambda:REGION:ACCOUNT_ID:function:my-function; //run.googleapis.com/projects/PROJECT_ID/locations/LOCATION_ID/services/SERVICE_ID; /subscriptions/<SUBSCIPTION_GUID>/resourceGroups/<RG>/providers/Microsoft.Web/sites/<FUNCAPP>/functions/<FUNC>	Recommended
faas.instance	string	The execution environment ID as a string, that will be potentially reused for other invocations to the same function/function version. [3]	2021/06/28/[$LATEST]2f399eb14537447da05ab2a2e39309de	Recommended
faas.max_memory	int	The amount of memory available to the serverless function converted to Bytes. [4]	134217728	Recommended
faas.version	string	The immutable version of the function being executed. [5]	26; pinkfroid-00002	Recommended

[1]: This is the name of the function as configured/deployed on the FaaS platform and is usually different from the name of the callback function (which may be stored in the code.namespace/code.function span attributes).

For some cloud providers, the above definition is ambiguous. The following definition of function name MUST be used for this attribute (and consequently the span name) for the listed cloud providers/products:

• Azure: The full name <FUNCAPP>/<FUNC>, i.e., function app name followed by a forward slash followed by the function name (this form can also be seen in the resource JSON for the function). This means that a span attribute MUST be used, as an Azure function app can host multiple functions that would usually share a TracerProvider (see also the cloud.resource_id attribute).

[2]: On some cloud providers, it may not be possible to determine the full ID at startup, so it may be necessary to set cloud.resource_id as a span attribute instead.

The exact value to use for cloud.resource_id depends on the cloud provider. The following well-known definitions MUST be used if you set this attribute and they apply:

• AWS Lambda: The function ARN. Take care not to use the “invoked ARN” directly but replace any alias suffix with the resolved function version, as the same runtime instance may be invocable with multiple different aliases.
• GCP: The URI of the resource
• Azure: The Fully Qualified Resource ID of the invoked function, not the function app, having the form /subscriptions/<SUBSCIPTION_GUID>/resourceGroups/<RG>/providers/Microsoft.Web/sites/<FUNCAPP>/functions/<FUNC>. This means that a span attribute MUST be used, as an Azure function app can host multiple functions that would usually share a TracerProvider.

[3]: * AWS Lambda: Use the (full) log stream name.

[4]: It’s recommended to set this attribute since e.g. too little memory can easily stop a Java AWS Lambda function from working correctly. On AWS Lambda, the environment variable AWS_LAMBDA_FUNCTION_MEMORY_SIZE provides this information (which must be multiplied by 1,048,576).

[5]: Depending on the cloud provider and platform, use:

• AWS Lambda: The function version (an integer represented as a decimal string).
• Google Cloud Run (Services): The revision (i.e., the function name plus the revision suffix).
• Google Cloud Functions: The value of the K_REVISION environment variable.
• Azure Functions: Not applicable. Do not set this attribute.

Note: The resource attribute faas.instance differs from the span attribute faas.invocation_id. For more information see the Semantic conventions for FaaS spans.

Using span attributes instead of resource attributes

There are cases where a FaaS resource attribute is better applied as a span attribute instead. See the FaaS trace conventions for more.