Prometheus Monitoring for Java Web Applications w o Modifying Source Code
summary
Creates a Java agent that injects Prometheus counters into servlet code at class-load time using Byte Buddy, instruments javax.servlet.Servlet.service to increment a labeled counter for the request path, and starts a tiny HTTP exporter so metrics appear at /metrics on :9300. Works against WildFly (and also Tomcat/Spring Boot), demo shows counters incrementing on each request. Notes: must expose agent packages to app server classloader (JBoss module tweak) and use thread‑locals to avoid double counting when servlets forward.
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chapters (9)
- 0:00Prometheus monitoring intro
- 1:08What is a Prometheus metric
- 6:02Instrumenting Java apps
- 12:30Monitoring without code changes
- 13:33How Java agents work
- 16:22Byte Buddy for bytecode
- 18:49Demo of Java agent
- 23:28Advanced use cases
- 27:48Q&A and server setup
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