Semantic Conventions for FaaS Metrics

Status: Experimental

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.

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.

This metric SHOULD be specified with ExplicitBucketBoundaries 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 ].

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.invoke_duration	Histogram	s	Measures the duration of the function’s logic execution

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.init_duration

This metric is recommended.

This metric SHOULD be specified with ExplicitBucketBoundaries 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 ].

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

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.coldstarts

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.coldstarts	Counter	{coldstart}	Number of invocation cold starts

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.errors

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.errors	Counter	{error}	Number of invocation errors

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.invocations

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.invocations	Counter	{invocation}	Number of successful invocations

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.timeouts

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.timeouts	Counter	{timeout}	Number of invocation timeouts

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.mem_usage

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.mem_usage	Histogram	By	Distribution of max memory usage per invocation

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.cpu_usage

This metric is recommended.

This metric SHOULD be specified with ExplicitBucketBoundaries 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 ].

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.cpu_usage	Histogram	s	Distribution of CPU usage per invocation

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

Metric: faas.net_io

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
faas.net_io	Histogram	By	Distribution of net I/O usage per invocation

Attribute	Type	Description	Examples	Requirement Level	Stability
faas.trigger	string	Type of the trigger which caused this function invocation.	datasource	Recommended

faas.trigger MUST be one of the following:

Value	Description	Stability
datasource	A response to some data source operation such as a database or filesystem read/write
http	To provide an answer to an inbound HTTP request
pubsub	A function is set to be executed when messages are sent to a messaging system
timer	A function is scheduled to be executed regularly
other	If none of the others apply

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
• AWS Lambda Insight Metrics
• Azure Functions Metrics
• Google CloudFunctions Metrics
• OpenFaas Metrics