Troubleshooting Flight Recorder with WildFly/EAP

In the world of Java application servers, WildFly and RedHat JBoss Enterprise Application Platform (EAP) stand out as prominent choices for deploying and running enterprise-level applications. These application servers provide a robust and reliable environment for Java applications, but like any software, they may encounter performance issues that necessitate troubleshooting.

One of the powerful tools available for diagnosing performance problems in Java applications is Flight Recorder. Flight Recorder is a profiling and event collection framework built into the Java Virtual Machine (JVM) that provides detailed insights into the behavior of Java applications. In this blog post, we will explore how to troubleshoot performance issues using Flight Recorder with WildFly and EAP.

Enabling Flight Recorder in WildFly/EAP

Flight Recorder is available in commercial versions of the Oracle JDK and in OpenJDK. To use Flight Recorder with WildFly or EAP, you will need to ensure that you are running the appropriate JDK version and that the Flight Recorder module is enabled in the server configuration.

JDK Version

It's essential to use a JDK version that includes Flight Recorder. For Oracle JDK, Flight Recorder is included starting from Oracle JDK 7u40. When using OpenJDK, Flight Recorder is available in OpenJDK Mission Control, which is an open-source project that provides tools for monitoring and managing Java applications.

Configuration

To enable Flight Recorder in WildFly or EAP, you need to ensure that the JVM is started with the necessary options. This can be achieved by adding the following options to the JVM startup parameters:

-XX:+UnlockCommercialFeatures -XX:+FlightRecorder

These options unlock the commercial features (required for Flight Recorder) and enable Flight Recorder in the JVM.

Recording a Flight Recording

Once Flight Recorder is enabled, you can record a flight recording to capture information about the behavior of the Java application during a specific time period or in response to particular events. Recording a flight recording involves specifying which events to record and for how long.

Using JCMD

To start a flight recording, you can use the jcmd tool, which is included with the JDK. First, identify the process ID (PID) of the WildFly or EAP server using:

jcmd

Then, start the flight recording by executing:

jcmd <PID> JFR.start name=myrecording duration=180s filename=myrecording.jfr

In this example, we start a flight recording with the name "myrecording" for a duration of 180 seconds, and the recording is saved to the file "myrecording.jfr".

Using JConsole

Alternatively, you can use JConsole, a graphical tool for monitoring and managing Java applications. JConsole provides a user-friendly interface for starting and controlling flight recordings.

Analyzing a Flight Recording

Once you have captured a flight recording, you can analyze it to gain insights into the behavior of the Java application. Flight Recorder produces comprehensive data about various aspects of the JVM and the running application, including CPU usage, memory allocation, garbage collection, and thread activity.

Java Mission Control

Java Mission Control (JMC) is a powerful tool for analyzing flight recordings. It provides a rich set of visualizations and tools for inspecting the data collected during the flight recording. JMC allows you to navigate through the recorded events, view detailed telemetry data, and identify performance bottlenecks in the application.

Troubleshooting Performance Issues

When analyzing a flight recording, pay close attention to areas such as:

• CPU Usage: Identify which parts of the application are consuming the most CPU time.
• Memory Allocation: Look for excessive object allocations and memory churn.
• Garbage Collection: Check for patterns of garbage collection activity that may indicate inefficient memory management.
• Thread Activity: Analyze thread behavior and look for potential contention or deadlocks.

By examining these areas, you can pinpoint performance issues and gain a better understanding of the application's runtime behavior.

My Closing Thoughts on the Matter

Troubleshooting performance issues in Java applications running on WildFly or EAP can be challenging, but with the powerful capabilities of Flight Recorder, you can gain deep insights into the runtime behavior of your applications. Enabling Flight Recorder, recording flight recordings, and analyzing the captured data can help you identify and resolve performance bottlenecks, ultimately leading to a more efficient and stable application environment.

In conclusion, Flight Recorder is a valuable tool in the arsenal of any Java developer or system administrator, and mastering its usage can greatly enhance the performance troubleshooting capabilities of WildFly and EAP. By leveraging Flight Recorder effectively, you can ensure that your Java applications are running at their best.

For further reference and learning, check out the official documentation for Java Flight Recorder and Java Mission Control to delve deeper into the capabilities and usage of these tools.

With the knowledge gained from this guide, you can confidently employ Flight Recorder to troubleshoot and optimize your Java applications running on WildFly and EAP.