micrometer-metrics/micrometer

Timer API does not support Kotlin suspend function (coroutines)

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#4,455 opened on Dec 7, 2023

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enhancementhelp wantedkotlin

Description

Please describe the feature request.

For standard (non suspend functions) it is possible to use record function to measure method invocation time:

Timer.builder("method.timed")
            .register(meterRegistry)
            .record { fn() } // fn() is a standard, non suspend function

However, it is not possible to call a suspend function from within record block:

Timer.builder("method.timed")
            .register(meterRegistry)
            .record { suspendFn() } // Suspension functions can be called only within coroutine body

The support for suspend functions should be added to the library.

Rationale Suspend functions are popular for non-blocking API, and it is currently not possible to measure time needed to call suspend functions without having a custom function to record the time.

Additional context Maybe this could be added as a extension function to the Timer interface.

Contributor guide

Tech stack
kotlinjava
Domain
observabilityperformance
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Kotlin suspend functionsMicrometer Timer API
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Review the existing Timer.record function for non suspend functions to understand the pattern. Add a new suspend extension function for Timer that accepts a suspending lambda. Check the micrometer source for existing coroutine support patterns (e.g., in reactor or kotlinx coroutines). Consider adding the function in a Kotlin specific module if available. Consult comments on the issue for any maintainer guidance.
Timer API does not support Kotlin suspend function (coroutines) · micrometer-metrics/micrometer#4455 | Good First Issue