How to collect Java Flight Recorder (JFR) data for troubleshooting application performance

Java Flight Recorder (JFR) is a tool for helping debug many kinds of performance issues.  JFR captures a large set of JVM performance information into a flight recording file.  The recording can then be analyzed offline using Java Mission Control.

Note: JFR is not available on IBM JREs.  Please see - How to generate a YourKit session if using an IBM JRE.

OpenJDK 8u262 and 11+

JFR is available in OpenJDK 11+.  Additionally, it was back-ported to OpenJDK 8u262, so all recent OpenJDK 1.8 distributions should have JFR available.

We normally ask that you capture a profiling recording via modifying the settings property to settings=profile.

# Record to file "recording.jfr", use the settings "profile"
-XX:StartFlightRecording=filename=recording.jfr,settings=profile

# Record to file "recording.jfr", record for 5mins before dumping results, use the settings "profile"
-XX:StartFlightRecording=filename=recording.jfr,duration=300s,settings=profile

# Record to file "recording.jfr", delay starting recording for 30s, use the settings "profile"
-XX:StartFlightRecording=filename=recording.jfr,delay=30s,settings=profile

Recording to disk manually using jcmd

The following example recording to disk and using jcmd requires a JDK install and access to the server/container running the application. For example:

-XX:StartFlightRecording=disk=true,name=recording-1,filename=/tmp/agent.jfr,maxage=15m,dumponexit=true,settings=profile

Then, log in to the application server and run jcmd to find the process ID.

Then, run jcmd <PID> JFR.dump filename=/recording.jfr to record the data.

See also:

• Java Agent Effects on Application Performance (Assess)
• Java Agent Effects on Startup Performance
• Red Hat Customer Portal - Using JDK Flight Recorder with OpenJDK