micrometer-metrics/micrometer

System memory metrics

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#5234 opened on Jun 27, 2024

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 (9 comments) (1 reaction) (0 assignees)Java (4,220 stars) (935 forks)batch import
enhancementhelp wantedinstrumentationmodule: micrometer-core

Description

The class JvmMemoryMetrics offers memory metrics, but those are all related to heap and non heap values and do not expose the actual memory limits of the machine/container on which the application is running.

It'd be an improvement to offer some additional metrics in this class, such as system.memory.max system.memory.used

The metrics are available in the OperatingSystemMXBean classes in the Oracle and IBM JREs, and are already used by Micrometer to expose CPU metrics in the class io.micrometer.core.instrument.binder.system.ProcessorMetrics.

My use case would be to measure my application running inside a container in Kubernetes. With these metrics I would be able to know the percentage of available memory being used by the application.

The io.micrometer.core.instrument.binder.jvm.JvmMemoryMetrics is not enough to do it. For instance, by default Metaspace size is unlimited and Micrometer returns -1 when trying to read it.

The most important metric missing is getTotalPhysicalMemorySize, without it there's no way to build a Grafana panel that shows the percentage of memory being used by an application.

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.
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
Java basicsMicrometer APIJVM metricsOperatingSystemMXBean
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60
Research direction
The issue requests adding system memory metrics (system.memory.max, system.memory.used) to the JvmMemoryMetrics class. The data is available via OperatingSystemMXBean in Java (Oracle and IBM JREs). Review the existing ProcessorMetrics class in io.micrometer.core.instrument.binder.system for reference on how to bind OS metrics. The implementation should follow similar patterns to expose new gauge metrics.