micrometer-metrics/micrometer

Cache metrics for http clients

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#1,700 opened on Nov 11, 2019

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 (2 comments) (2 reactions) (0 assignees)Java (4,220 stars) (935 forks)batch import
enhancementhelp wantedwaiting for feedback

Description

Both httpclient from Apache and OkHttp (which are instrumented by micrometer: OkHttpMetricsEventListener and https://github.com/micrometer-metrics/micrometer/issues/533) support provider driven caching (based on http headers)

It would be helpful (for the sake of completeness) for micrometer to provide insight to the state of caches (size, maxSize, hit and misses).

I've drafted a cache metrics for OkHttp which I'd like to get feedback ok: https://github.com/micrometer-metrics/micrometer/compare/master...kubamarchwicki:httpclient-cache-metrics. If that's something interesting, I'd hapilly finalize both OkHttp as well as httpclient.

Contributor guide

Tech stack
java
Domain
observability
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.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
JavaMicrometerOkHttp caching
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Review the linked draft PR for OkHttp cache metrics. Understand the existing OkHttpMetricsEventListener class. Implement cache metrics by following the Micrometer binder pattern. Then replicate for Apache HttpClient, referencing its cache module. Ensure proper testing and documentation.