advanced~4h
Heap Monitoring and JFR
Moving from GC theory to actually looking at a running JVM: live heap monitoring with VisualVM and jcmd, capturing and reading a heap dump to find a leak, Java Flight Recorder (JFR) fundamentals, and a Spring Boot production incident worked end-to-end with these tools.
Learning objectives
- Use jcmd and VisualVM to observe a live JVM's heap usage and GC activity without restarting it
- Capture a heap dump and explain what a 'soft leak' is as distinct from a classic reference leak
- Read a heap dump's dominator/retained-size view to find what's actually holding a suspected leak alive
- Explain what Java Flight Recorder captures and why its overhead is low enough to run in production
- Walk a Spring Boot production memory incident end-to-end using these tools in the right order
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Heap Monitoring and JFR