At this year’s [FOSDEM] conference I did a 30 minutes presentation on [Monitoring Legacy Java Applications with Prometheus]. The talk gives an overview of some of the options you have for monitoring Java applications with [Prometheus] when you cannot modify the application’s source code:

• Logfile monitoring ([grok_exporter]), and how it differs from [Elastic stack]
• Blackbox monitoring ([blackbox_exporter])
• JMX ([jmx_exporter])
• Write your own Java agent ([promagent.io])

The video is available below.

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The Prometheus monitoring tool follows a white-box monitoring approach: Applications actively provide metrics about their internal state to the Prometheus server. In order to instrument an application with Prometheus metrics, you have to add a metrics library and use that library in the application’s source code. However, DevOps teams do not always have the option to modify the source code of the applications they are running.

Promagent is a Java agent using Bytecode manipulation for instrumenting Java Web applications without modifying their source code. Promagent allows you to get white-box metrics for Java Web applications even if these applications do not implement any metrics library out-of-the-box.

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