How to get a rolling recording into disk, with a maximum age?
When something goes bad in my server, I want to be able to dump the profiling information of the hours prior and analyse it, to know what went wrong.
So, in other words, I wanted the JDK to save the recordings continuously to disk, but remove the older files/recordings such that the total amount remains under a certain threshold (age or size).
To that end, these are the options I have for version Oracle JDK 1.8.0_144:
-XX:+UnlockCommercialFeatures
-XX:+FlightRecorder
-XX:StartFlightRecording
name=<foo-bar>
-XX:FlightRecorderOptions
defaultrecording=true // what does this do even?
disk=true
maxage=1h // this is what I thought would solve my problem!
repository=<path-to-where-I-want-the-recording>
maxchunksize=5M
I would have thought that setting maxage=1h would only keep the last 1 hour of recording on disk. But no! Its been past 1 day, and the files are not being capped.
At the same time the maxchunksize appears to work. The various .jfr files have approximately 5M. Of which there are many such files, since the the age capped is not being enforced.
What am I doing wrong?
The problem, I think, is that you are starting two recordings, one with-XX:StartFlightRecording and one with -XX:FlightRecorderOptions=defaultrecording=true.
The one with -XX:StartFlightRecording is unbounded. I think the following would be appropriate option for Oracle JDK 1.8.0_144 and your use case:
-XX:+UnlockCommercialFeatures
-XX:FlightRecorderOptions=repository=<path>
-XX:StartFlightRecording=maxage=1h,name=<name>
-XX:+UnlockCommercialFeatures is needed because JFR is a commercial feature in Oracle JDK 8. From JDK 11, it's no longer needed.
-XX:+FlightRecorder is not needed for JDK 8u40 or later. The JFR buffers are now setup when the first recording is started, not when the JVM starts.
-XX:FlightRecorderOptions=defaultrecording=true does a lot of things, mostly for historical reasons, but only needed when doing in-memory recordings. From JDK 9, the option is never needed and has been removed.
-XX:FlightRecorderOptions=disk=true,maxage=1h isn't needed if -XX:StartFlightRecording is used, which is the recommended way to start JFR.
Unless you have an issue, I would keep the maxchunksize at the default (12 MB). It's the chunk files size JFR has been optimized for and tested against.
I am accepting Kire Haglin's answer.
Adding a bit more value for what worked for me on this JDK:
-XX:+UnlockCommercialFeatures
-XX:StartFlightRecording
name=<foo-bar>
maxage=12h
dumponexit=true
-XX:FlightRecorderOptions
dumponexitpath=<path-to-file>.jfr
disk=true
repository=<some-folder-path>
Notice the extra parameters dumponexit and dumponexitpath, not present on my original question. I ended up also needing those.
After trial and error, it appears dumponexit must exist within the XX:StartFlightRecording argument, and dumponexitpath on the FlightRecorderOptions argument. No other arrangement seems to work.
Notice also that removing -XX:+FlightRecorder and defaultrecording=true (as Kire suggested) still worked. That being said, I don't think the presence of defaultrecording=true was triggering a double recording.
I am saying this because when issuing command jcmd <PID> JFR.check <name> I only got one entry.