Demo Monitoring using Java Melody

In this guide, you will learn how to monitor your Jenkins controller and agents using JavaMelody, an open-source performance monitoring tool for Java applications. By the end, you’ll be able to track real-time metrics such as memory usage, CPU load, HTTP requests, and thread activity directly within your Jenkins UI.

What Is JavaMelody?

JavaMelody provides in-depth dashboards for JavaEE applications, capturing critical performance data:

The image shows a GitHub wiki page for JavaMelody, a tool for monitoring JavaEE applications, featuring a screenshot of its monitoring interface.

Key metrics tracked by JavaMelody:

Memory usage (heap & non-heap)
CPU load and system load averages
HTTP request counts, mean/max durations
Thread states and peak thread counts
Error rates and log analysis

Note

JavaMelody supports HTML and PDF report generation, multi-language UI, and integrates seamlessly into any Java web application.

Integrating JavaMelody with Jenkins

Jenkins is Java-based, so you can leverage the Monitoring plugin to embed JavaMelody into your controller and agents.

Go to Manage Jenkins > Manage Plugins.
Search for Monitoring and install the plugin.
Restart your Jenkins controller to activate JavaMelody.

Warning

Installing monitoring plugins may introduce additional JVM overhead. Monitor resource usage on production systems before rolling out cluster-wide.

For full documentation, visit the Monitoring Plugin page.

The image shows a webpage for the Jenkins Monitoring plugin, detailing its features, version information, and installation statistics. It includes links to documentation, GitHub, and issue tracking, along with a summary of the plugin's capabilities.

Plugin Features

Metric Category	Details
Memory & CPU	Heap/non-heap usage, system CPU, process CPU, load averages
HTTP Requests	Request counts, cumulative times, mean/max durations
Thread Monitoring	Active vs. idle threads, creation rate, peak usage
Errors & Logs	Exception counts, log severity breakdown
Reporting	Export HTML or PDF reports
Localization	English, German, French, and more

Accessing the Monitoring Dashboard

After restarting Jenkins, navigate to Manage Jenkins and scroll down to the Monitoring of Jenkins Instance and Monitoring of Jenkins Agents sections:

The image shows a Jenkins management interface with options for security, status information, troubleshooting, and tools and actions. It includes sections for monitoring Jenkins instances, system logs, and managing old data.

Controller (Jenkins Instance) Monitoring

Click Monitoring of Jenkins Instance to open the JavaMelody dashboard for your controller. You’ll find:

System Information
- JVM vendor/version, OS name, uptime
Memory & CPU Charts
- Real-time graphs for heap/non-heap and CPU usage
HTTP Request Statistics
- Table of endpoints with hits, cumulative time, mean/max durations
Thread States
- Active vs. idle threads, thread creation rate

The image shows a performance monitoring dashboard for HTTP requests, displaying statistics such as cumulative time, hits, mean time, and maximum time for various requests. It includes a table with detailed metrics and a small graph indicating mean and maximum times over a period.

At the top, adjust the time window for all charts or click PDF report to export metrics for sharing.

Agent (Node) Monitoring

Under Monitoring of Jenkins Agents, select any connected node to view:

Garbage collection triggers
Heap dump generation
Memory histogram visualizations
Active HTTP session details (client country, browser, user)

If only one agent is online, data will be limited, but additional nodes will appear as they connect.

Observing Live Build Metrics

To see JavaMelody update in real time:

Create a Jenkins pipeline with a sleep/pause stage (e.g., sleep 60).
Trigger the job and keep the monitoring dashboard open.
Refresh periodically to watch thread counts rise, HTTP sessions form, and CPU usage spike.

The image shows a JavaMelody monitoring dashboard for a Jenkins server, displaying system errors, current requests, system information, and thread details.

In the Threads section, you’ll observe:

Total vs. active threads
Thread creation rate spikes during builds
Peak usage metrics

Real-time insights help you identify bottlenecks and optimize Jenkins performance.

Links and References

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