Java EE (Java Enterprise Edition) General Discussion

Thanks Erik, adding disk=true did the trick.

I've found that the documentation and functionality of the -XX:StartFlightRecording and -XX:FlightRecorderOptions is very unclear and confusing.  Can you or others comment/clarify the following?

• Is it correct that the XX:StartFlightRecording options are meant to only apply to a special start recording (that starts at server start time), while the XX:FlightRecorderOptions are meant to apply to any/all recordings?
• Why are some of the XX:FlightRecorderOptions not also available for XX:StartFlightRecording, e.g., disk=true, dumponexit=true?  This makes it tricky to configure the start recording as you need to specify different options with different XX: parameters.
• The settings=path option seems to have no effect when given to XX:FlightRecorderOptions, even though it's listed in the documentation page above as being a supported option.  When I use settings=path with XX:FlightRecorderOptions, I still get the default settings.  Is this a known implementation or documentation bug?
• With both XX:StartFlightRecording and XX:FlightRecorderOptions, what's the behavior when defaultrecording=false?  The documentation says "Specifies whether the recording is a continuous background recording or it runs for a limited time. By default, this parameter is set to false (recording runs for a limited time)."  What is this limited time (how long)?  And is it a limited time forward from the beginning, or backwards from the current time?  Why is this setting even needed given the maxage, maxsize, and duration settings?

thanks,

Chris

"Is it correct that the XX:StartFlightRecording options are meant to only apply to a special start recording (that starts at server start time), while the XX:FlightRecorderOptions are meant to apply to any/all recordings"

-XX:FlightRecorderOptions is meant to configure global settings, but there are also options that controls the default in-memory recording (called "Hotspot default"), which can be turned on by setting defaultrecording=true. Since Flight Recorder records the union of all ongoing recordings, it will in practise apply to other recordings as well.

"The settings=path option seems to have no effect when given to XX:FlightRecorderOptions, even though it's listed in the documentation page above as being a supported option.  When I use settings=path with XX:FlightRecorderOptions, I still get the default settings.  Is this a known implementation or documentation bug?"

It's a known bug, as a workaround you can replace the file named default.jfc in JRE_HOME/lib/jfr with the settings file you want, i.e profile.jfc

"With both XX:StartFlightRecording and XX:FlightRecorderOptions, what's the behavior when defaultrecording=false?  "

No default (in-memory) recording will be started

"The documentation says "Specifies whether the recording is a continuous background recording or it runs for a limited time. By default, this parameter is set to false (recording runs for a limited time)." What is this limited time (how long)?  And is it a limited time forward from the beginning, or backwards from the current time?  Why is this setting even needed given the maxage, maxsize, and duration settings?"

It's incorrect, defaultrecording=true is just a convenience option for starting the default in-memory recording. There is no limit put in place if you set it to false.

If you want to use a disk repository, you can ignore all options that includes the word "default" and just use -XX:StartFlightRecording.

Thanks Erik.

If you want to use a disk repository, you can ignore all options that includes the word "default" and just use -XX:StartFlightRecording.

I found that even when I use -XX:StartFlightRecording, I can only get that recording dumped to disk on exit if I set defaultrecording=true along with disk=true,dumponexit=true,dumponexitpath=path via -XX:FlightRecorderOptions .

Chris

ctoomey wrote:

Thanks Erik.

If you want to use a disk repository, you can ignore all options that includes the word "default" and just use -XX:StartFlightRecording.

I found that even when I use -XX:StartFlightRecording, I can only get that recording dumped to disk on exit if I set defaultrecording=true along with disk=true,dumponexit=true,dumponexitpath=path via -XX:FlightRecorderOptions .

Chris

You should be able dump the buffers on exit, even if you haven't started a defaultrecording.

I will file a bug report. Thanks for reporting.