Java Mission Control Listener?

Question

I currently have some Java code that I would like to profile. I decided to use Java Mission Control after reading some promising things about it. However, every resource I've consulted so far tells me to first start the process I want to profile first, and only then "attach" or profile the code from Mission Control once it is already running (for example this video from oracle: https://youtu.be/WMEpRUgp9Y4?t=14m56s ).

Is there a way to start the process with profiling from the start? Thanks

Answer 1

There is a way to start a profiling recording when you start the process.

Example: Running a profiling recording for 10 minutes.

java -XX:+UnlockDiagnosticVMOptions -XX:+DebugNonSafepoints -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=duration=10m,name=Test,filename=recording.jfr,settings=profile -jar target/highcpu-0.0.1.jar

See my article for more details: Using Java Flight Recorder

Answer 2

It's not very well documented but there is the possibility. You need to use this jvm options

-XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:FlightRecorderOptions=

The first two are mandatory while the last one need to be configured with various parameters that you can find explained here . It's not straightforward to understand the meaning of each parameter but with some trial and error you can find a good set of option pretty easily.

Just as reference this one is a minimal functional configuration:

java -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:FlightRecorderOptions=defaultrecording=true,disk=true,repository=/tmp,maxage=6h,settings=default MyApp

Answer 3

JDK 11:

-XX:StartFlightRecording

JDK 9, JDK 10:

-XX:+UnlockCommercialFeatures
-XX:StartFlightRecording

JDK 8u40,

-XX:+UnlockCommercialFeatures
-XX:StartFlightRecording=name=whatever

JDK 7u4, JDK 8u20:

-XX:+UnlockCommercialFeatures 
-XX:+FlightRecorder 
-XX:StartFlightRecording=name=whatever

If you want to avoid attaching to the process all together, you can specify a filename, ie -XX:StartFlightRecording=filename=rec.jfr, and then either dump the recording after a period by setting a duration, ie duration=60s, or if you only want it to happen when the JVM exits:

 -XX:StartFlightRecording=
 filename=rec.jfr,dumponexit=true

You can the open then open recording file in JMC. In JDK 11, this has been simplified further so you only need to specify:

 -XX:StartFlightRecording:filename=c:\recs

and the filename will be generated in the specified directory and it will automatically dump when the JVM exits.