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# Semantic conventions for FaaS metrics

**Status**: [Development][DocumentStatus]

This document defines how to describe an instance of a function that runs without provisioning
or managing of servers (also known as serverless functions or Function as a Service (FaaS)) with metrics.

The conventions described in this section are FaaS (function as a service) specific. When FaaS operations occur,
metric events about those operations will be generated and reported to provide insights into the
operations. By adding FaaS attributes to metric events it allows for finely tuned filtering.

<!-- toc -->

- [Metric Instruments](#metric-instruments)
  - [FaaS Instance](#faas-instance)
    - [Metric: `faas.invoke_duration`](#metric-faasinvoke_duration)
    - [Metric: `faas.init_duration`](#metric-faasinit_duration)
    - [Metric: `faas.coldstarts`](#metric-faascoldstarts)
    - [Metric: `faas.errors`](#metric-faaserrors)
    - [Metric: `faas.invocations`](#metric-faasinvocations)
    - [Metric: `faas.timeouts`](#metric-faastimeouts)
    - [Metric: `faas.mem_usage`](#metric-faasmem_usage)
    - [Metric: `faas.cpu_usage`](#metric-faascpu_usage)
    - [Metric: `faas.net_io`](#metric-faasnet_io)
- [References](#references)
  - [Metric References](#metric-references)

<!-- tocstop -->

## Metric Instruments

The following metric instruments describe FaaS operations.

### FaaS Instance

The following metrics are recorded by the FaaS instance.

#### Metric: `faas.invoke_duration`

This metric is [recommended][MetricRecommended].

This metric SHOULD be specified with
[`ExplicitBucketBoundaries`](https://github.com/open-telemetry/opentelemetry-specification/tree/v1.43.0/specification/metrics/api.md#instrument-advisory-parameters)
of `[ 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10 ]`.

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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.invoke_duration` | Histogram | `s` | Measures the duration of the function's logic execution | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

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#### Metric: `faas.init_duration`

This metric is [recommended][MetricRecommended].

This metric SHOULD be specified with
[`ExplicitBucketBoundaries`](https://github.com/open-telemetry/opentelemetry-specification/tree/v1.43.0/specification/metrics/api.md#instrument-advisory-parameters)
of `[ 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10 ]`.

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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.init_duration` | Histogram | `s` | Measures the duration of the function's initialization, such as a cold start | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

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#### Metric: `faas.coldstarts`

This metric is [recommended][MetricRecommended].

<!-- semconv metric.faas.coldstarts -->
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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.coldstarts` | Counter | `{coldstart}` | Number of invocation cold starts | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

<!-- markdownlint-restore -->
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#### Metric: `faas.errors`

This metric is [recommended][MetricRecommended].

<!-- semconv metric.faas.errors -->
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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.errors` | Counter | `{error}` | Number of invocation errors | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

<!-- markdownlint-restore -->
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<!-- endsemconv -->

#### Metric: `faas.invocations`

This metric is [recommended][MetricRecommended].

<!-- semconv metric.faas.invocations -->
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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.invocations` | Counter | `{invocation}` | Number of successful invocations | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

<!-- markdownlint-restore -->
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<!-- endsemconv -->

#### Metric: `faas.timeouts`

This metric is [recommended][MetricRecommended].

<!-- semconv metric.faas.timeouts -->
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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.timeouts` | Counter | `{timeout}` | Number of invocation timeouts | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

<!-- markdownlint-restore -->
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<!-- endsemconv -->

#### Metric: `faas.mem_usage`

This metric is [recommended][MetricRecommended].

<!-- semconv metric.faas.mem_usage -->
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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.mem_usage` | Histogram | `By` | Distribution of max memory usage per invocation | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

<!-- markdownlint-restore -->
<!-- prettier-ignore-end -->
<!-- END AUTOGENERATED TEXT -->
<!-- endsemconv -->

#### Metric: `faas.cpu_usage`

This metric is [recommended][MetricRecommended].

This metric SHOULD be specified with
[`ExplicitBucketBoundaries`](https://github.com/open-telemetry/opentelemetry-specification/tree/v1.43.0/specification/metrics/api.md#instrument-advisory-parameters)
of `[ 0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10 ]`.

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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.cpu_usage` | Histogram | `s` | Distribution of CPU usage per invocation | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

<!-- markdownlint-restore -->
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<!-- endsemconv -->

#### Metric: `faas.net_io`

This metric is [recommended][MetricRecommended].

<!-- semconv metric.faas.net_io -->
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| Name     | Instrument Type | Unit (UCUM) | Description    | Stability |
| -------- | --------------- | ----------- | -------------- | --------- |
| `faas.net_io` | Histogram | `By` | Distribution of net I/O usage per invocation | ![Development](https://img.shields.io/badge/-development-blue) |

| Attribute  | Type | Description  | Examples  | [Requirement Level](https://opentelemetry.io/docs/specs/semconv/general/attribute-requirement-level/) | Stability |
|---|---|---|---|---|---|
| [`faas.trigger`](/docs/attributes-registry/faas.md) | string | Type of the trigger which caused this function invocation. | `datasource`; `http`; `pubsub` | `Recommended` | ![Development](https://img.shields.io/badge/-development-blue) |

---

`faas.trigger` has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

| Value  | Description | Stability |
|---|---|---|
| `datasource` | A response to some data source operation such as a database or filesystem read/write | ![Development](https://img.shields.io/badge/-development-blue) |
| `http` | To provide an answer to an inbound HTTP request | ![Development](https://img.shields.io/badge/-development-blue) |
| `other` | If none of the others apply | ![Development](https://img.shields.io/badge/-development-blue) |
| `pubsub` | A function is set to be executed when messages are sent to a messaging system | ![Development](https://img.shields.io/badge/-development-blue) |
| `timer` | A function is scheduled to be executed regularly | ![Development](https://img.shields.io/badge/-development-blue) |

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<!-- endsemconv -->

## References

### Metric References

Below are links to documentation regarding metrics that are available with different
FaaS providers. This list is not exhaustive.

* [AWS Lambda Metrics](https://docs.aws.amazon.com/lambda/latest/dg/monitoring-metrics.html)
* [AWS Lambda Insight Metrics](https://docs.aws.amazon.com/AmazonCloudWatch/latest/monitoring/Lambda-Insights-metrics.html)
* [Azure Functions Metrics](https://docs.microsoft.com/azure/azure-monitor/platform/metrics-supported)
* [Google CloudFunctions Metrics](https://cloud.google.com/monitoring/api/metrics_gcp#gcp-cloudfunctions)
* [OpenFaas Metrics](https://docs.openfaas.com/architecture/metrics/)

[DocumentStatus]: https://opentelemetry.io/docs/specs/otel/document-status
[MetricRecommended]: /docs/general/metric-requirement-level.md#recommended
