How to Monitor Java Locks Using Java Flight Recorder and Java Mission Control?

What are the best practices for monitoring locks in Java applications using Java Flight Recorder and Java Mission Control?

// Example of enabling JFR in your Java application
// Java Flight Recorder is enabled by adding the following JVM option:
// -XX:StartFlightRecording=delay=0s,settings=jfr.default

Monitoring locks in Java applications is crucial for identifying performance bottlenecks and concurrency issues. Java Flight Recorder (JFR) is a powerful tool that allows developers to monitor the Java application performance, including lock contention. Java Mission Control (JMC) provides an interface to analyze the data collected by JFR and visualize it effectively.

// Command to start Java application with JFR enabled
java -XX:StartFlightRecording=delay=0s,settings=jfr.default -jar myapp.jar

Causes

• Contention caused by multiple threads attempting to access a shared resource simultaneously.
• Deadlocks resulting from circular dependencies between threads.
• Excessive locking which can degrade application responsiveness.

Solutions

• Enable Java Flight Recorder to collect data on thread states and lock events.
• Use Java Mission Control to analyze the recorded data for lock contention patterns.
• Optimize locking mechanisms by using finer-grained locks or lock-free data structures.

Mistake: Not enabling JFR correctly or forgetting JVM options.

Solution: Ensure that JVM options for JFR are included when starting the application to collect relevant data.

Mistake: Neglecting to analyze JFR recordings in JMC.

Solution: Regularly open the JFR recordings in Java Mission Control to review and analyze possible locking issues.