micrometer-metrics/micrometer

Log a warning when instrumenting a cache that is not recording stats

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#5066 opened on May 11, 2024

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 (2 comments) (0 reactions) (0 assignees)Java (4,220 stars) (935 forks)batch import
enhancementhelp wantedinstrumentationmodule: micrometer-core

Description

Please describe the feature request. It would be nice if a warning were logged (or the user was informed in some way) when a cache is instrumented that is not recording stats.

Rationale For some Cache implementations like Caffeine recording stats is optional. When instrumenting a cache that is not recording stats the meters will constantly report 0 which could be misleading. This is probably not what the user desires.

Additional context

apache/accumulo#4552

Contributor guide

Tech stack
java
Domain
observabilitybackend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaMicrometer cache instrumentation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
Look at the cache instrumentation code in Micrometer, likely in the `micrometer core` module under `io.micrometer.core.instrument.binder.cache`. Identify where the cache is instrumented (e.g., in `CacheMeterBinder` or similar). For Caffeine caches, check if `CacheStats` are enabled via `Caffeine.recordStats()`. If stats are not enabled, add a warning log using standard `Logger` before creating meters. The issue suggests that when instruments are created, they will report zero, so the warning should be emitted during instrumentation setup.