81 lines
4.7 KiB
Markdown
81 lines
4.7 KiB
Markdown
# Function as a Service
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**Status**: [Experimental](../../document-status.md)
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**type:** `faas`
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**Description:** A "function as a service" aka "serverless function" instance.
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See also:
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- The [Trace semantic conventions for FaaS](../../trace/semantic_conventions/faas.md)
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- The [Cloud resource conventions](cloud.md)
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## FaaS resource attributes
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<!-- semconv faas_resource -->
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| Attribute | Type | Description | Examples | Requirement Level |
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|---|---|---|---|---|
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| `faas.name` | string | The name of the single function that this runtime instance executes. [1] | `my-function`; `myazurefunctionapp/some-function-name` | Required |
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| `faas.id` | string | The unique ID of the single function that this runtime instance executes. [2] | `arn:aws:lambda:us-west-2:123456789012:function:my-function` | Recommended |
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| `faas.version` | string | The immutable version of the function being executed. [3] | `26`; `pinkfroid-00002` | Recommended |
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| `faas.instance` | string | The execution environment ID as a string, that will be potentially reused for other invocations to the same function/function version. [4] | `2021/06/28/[$LATEST]2f399eb14537447da05ab2a2e39309de` | Recommended |
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| `faas.max_memory` | int | The amount of memory available to the serverless function in MiB. [5] | `128` | Recommended |
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**[1]:** This is the name of the function as configured/deployed on the FaaS
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platform and is usually different from the name of the callback
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function (which may be stored in the
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[`code.namespace`/`code.function`](../../trace/semantic_conventions/span-general.md#source-code-attributes)
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span attributes).
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For some cloud providers, the above definition is ambiguous. The following
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definition of function name MUST be used for this attribute
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(and consequently the span name) for the listed cloud providers/products:
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* **Azure:** The full name `<FUNCAPP>/<FUNC>`, i.e., function app name
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followed by a forward slash followed by the function name (this form
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can also be seen in the resource JSON for the function).
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This means that a span attribute MUST be used, as an Azure function
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app can host multiple functions that would usually share
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a TracerProvider (see also the `faas.id` attribute).
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**[2]:** On some cloud providers, it may not be possible to determine the full ID at startup,
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so consider setting `faas.id` as a span attribute instead.
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The exact value to use for `faas.id` depends on the cloud provider:
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* **AWS Lambda:** The function [ARN](https://docs.aws.amazon.com/general/latest/gr/aws-arns-and-namespaces.html).
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Take care not to use the "invoked ARN" directly but replace any
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[alias suffix](https://docs.aws.amazon.com/lambda/latest/dg/configuration-aliases.html)
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with the resolved function version, as the same runtime instance may be invokable with
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multiple different aliases.
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* **GCP:** The [URI of the resource](https://cloud.google.com/iam/docs/full-resource-names)
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* **Azure:** The [Fully Qualified Resource ID](https://docs.microsoft.com/en-us/rest/api/resources/resources/get-by-id) of the invoked function,
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*not* the function app, having the form
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`/subscriptions/<SUBSCIPTION_GUID>/resourceGroups/<RG>/providers/Microsoft.Web/sites/<FUNCAPP>/functions/<FUNC>`.
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This means that a span attribute MUST be used, as an Azure function app can host multiple functions that would usually share
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a TracerProvider.
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**[3]:** Depending on the cloud provider and platform, use:
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* **AWS Lambda:** The [function version](https://docs.aws.amazon.com/lambda/latest/dg/configuration-versions.html)
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(an integer represented as a decimal string).
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* **Google Cloud Run:** The [revision](https://cloud.google.com/run/docs/managing/revisions)
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(i.e., the function name plus the revision suffix).
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* **Google Cloud Functions:** The value of the
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[`K_REVISION` environment variable](https://cloud.google.com/functions/docs/env-var#runtime_environment_variables_set_automatically).
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* **Azure Functions:** Not applicable. Do not set this attribute.
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**[4]:** * **AWS Lambda:** Use the (full) log stream name.
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**[5]:** 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.
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<!-- endsemconv -->
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Note: The resource attribute `faas.instance` differs from the span attribute `faas.execution`. For more information see the [Semantic conventions for FaaS spans](../../trace/semantic_conventions/faas.md#difference-between-execution-and-instance).
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## Using span attributes instead of resource attributes
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There are cases where a FaaS resource attribute is better applied as a span
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attribute instead.
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See the [FaaS trace conventions](../../trace/semantic_conventions/faas.md) for more.
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