Semantic Conventions for Node.js Runtime Metrics

Status: Experimental

This document describes semantic conventions for Node.js Runtime metrics in OpenTelemetry.

Experimental

Status: Experimental

Description: Experimental Node.js Runtime metrics captured under nodejs.

Note: The metrics for eventloop delay are split into separated values instead of a single histogram, because node runtime only returns single values through perf_hooks.monitorEventLoopDelay([options]) and not the entire histogram, so it’s not possible to convert it to an OpenTelemetry histogram.

Metric: nodejs.eventloop.delay.min

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.delay.min	Gauge	s	Event loop minimum delay. [1]

[1]: Value can be retrieved from value histogram.min of perf_hooks.monitorEventLoopDelay([options])

Metric: nodejs.eventloop.delay.max

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.delay.max	Gauge	s	Event loop maximum delay. [1]

[1]: Value can be retrieved from value histogram.max of perf_hooks.monitorEventLoopDelay([options])

Metric: nodejs.eventloop.delay.mean

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.delay.mean	Gauge	s	Event loop mean delay. [1]

[1]: Value can be retrieved from value histogram.mean of perf_hooks.monitorEventLoopDelay([options])

Metric: nodejs.eventloop.delay.stddev

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.delay.stddev	Gauge	s	Event loop standard deviation delay. [1]

[1]: Value can be retrieved from value histogram.stddev of perf_hooks.monitorEventLoopDelay([options])

Metric: nodejs.eventloop.delay.p50

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.delay.p50	Gauge	s	Event loop 50 percentile delay. [1]

[1]: Value can be retrieved from value histogram.percentile(50) of perf_hooks.monitorEventLoopDelay([options])

Metric: nodejs.eventloop.delay.p90

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.delay.p90	Gauge	s	Event loop 90 percentile delay. [1]

[1]: Value can be retrieved from value histogram.percentile(90) of perf_hooks.monitorEventLoopDelay([options])

Metric: nodejs.eventloop.delay.p99

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.delay.p99	Gauge	s	Event loop 99 percentile delay. [1]

[1]: Value can be retrieved from value histogram.percentile(99) of perf_hooks.monitorEventLoopDelay([options])

Metric: nodejs.eventloop.utilization

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.utilization	Gauge	1	Event loop utilization. [1]

[1]: The value range is [0.0, 1.0] and can be retrieved from performance.eventLoopUtilization([utilization1[, utilization2]])

Metric: nodejs.eventloop.time

This metric is recommended.

Name	Instrument Type	Unit (UCUM)	Description	Stability
nodejs.eventloop.time	Counter	s	Cumulative duration of time the event loop has been in each state. [1]

[1]: Value can be retrieved from performance.eventLoopUtilization([utilization1[, utilization2]])

Attribute	Type	Description	Examples	Requirement Level	Stability
nodejs.eventloop.state	string	The state of event loop time.	active; idle	Required

nodejs.eventloop.state 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
active	Active time.
idle	Idle time.