2 Java Flight Recorderの実行

例2-1 jcmdを使用した動的対話

例2-1では、商用機能をロック解除し、実行時に動的にJava Flight Recorderを有効化します。Javaアプリケーションの起動時に特別なオプションは指定されません。JVMが実行されると、jcmdコマンドのVM.unlock_commercial_featuresおよびJFR.startが使用され、商用機能がロック解除されて新しいフライト記録が開始されます。

$java -jar MyApp.jar
$jcmd 40019 VM.command_line
40019:
VM Arguments:
java_command: MyApp.jar
java_class_path (initial): MyApp.jar
Launcher Type: SUN_STANDARD

$jcmd 40019 VM.check_commercial_features
40019:
Commercial Features are locked.

$jcmd 40019 JFR.check
40019:
Java Flight Recorder not enabled.

Use VM.unlock_commercial_features to enable.

$jcmd 40019 VM.unlock_commercial_features
40019:
Commercial Features now unlocked.

$jcmd 40019 VM.check_commercial_features
40019:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has not been used.
Resource Management is disabled.

$jcmd 40019 JFR.check
40019:

No available recordings.

Use JFR.start to start a recording.

$jcmd 40019 JFR.start name=my_recording filename=myrecording.jfr dumponexit=true
40019:
Started recording 1. No limit (duration/maxsize/maxage) in use.

Use JFR.dump name=my_recording to copy recording data to file.

$jcmd 40019 VM.check_commercial_features
40019:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has been used.
  Resource Management is disabled.

$jcmd 40019 JFR.check
40019:
Recording: recording=1 name="my_recording" filename="myrecording.jfr" compress=false (running)

$

例2-2 -XX:+UnlockCommercialFeaturesおよび-XX:+FlightRecorderの使用

例2-2では、商用機能をロック解除してJFRを有効化するために、アプリケーションの起動時にjavaコマンドに-XX:+UnlockCommercialFeaturesオプションと-XX:+FlightRecorderオプションを渡します。

$java -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -jar MyApp.jar

$jcmd 37152 VM.command_line
37152:
VM Arguments:
jvm_args: -XX:+UnlockCommercialFeatures -XX:+FlightRecorder
java_command: MyApp.jar
java_class_path (initial): MyApp.jar
Launcher Type: SUN_STANDARD
$jcmd 37152 VM.check_commercial_features
37152:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has not been used.
  Resource Management is disabled.

$jcmd 37152 JFR.check
37152:
No available recordings.

Use JFR.start to start a recording.

$jcmd 37152 JFR.start name=my_recording filename=myrecording.jfr dumponexit=true
37152:
Started recording 1. No limit (duration/maxsize/maxage) in use.

Use JFR.dump name=my_recording to copy recording data to file.


$jcmd 37152 JFR.check
37152:
Recording: recording=1 name="my_recording" filename="myrecording.jfr" compress=false (running)

$jcmd 37152 VM.check_commercial_features
37152:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has been used.
  Resource Management is disabled.
$

例2-3 JFR動的起動での-XX:+UnlockCommercialFeaturesの使用

例2-3では、-XX:+UnlockCommercialFeaturesを使用してアプリケーションを起動した後に、JFR.startを使用してJFRを動的に起動します。

$java -XX:+UnlockCommercialFeatures -jar MyApp.jar

$jcmd 39970 VM.command_line
39970:
VM Arguments:
jvm_args: -XX:+UnlockCommercialFeatures
java_command: MyApp.jar
java_class_path (initial): MyApp.jar
Launcher Type: SUN_STANDARD

$jcmd 39970 VM.check_commercial_features
39970:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has not been used.
  Resource Management is disabled.

$jcmd 39970 JFR.check
39970:
No available recordings.

Use JFR.start to start a recording.

$jcmd 39970 VM.check_commercial_features
39970:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has not been used.
  Resource Management is disabled.

$jcmd 39970 JFR.start name=my_recording filename=myrecording.jfr dumponexit=true

39970:

Started recording 1. No limit (duration/maxsize/maxage) in use.

Use JFR.dump name=my_recording to copy recording data to file.

$jcmd 39970 VM.check_commercial_features

39970:

Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has been used.
  Resource Management is disabled.

$jcmd 39970 JFR.check
39970:
Recording: recording=1 name="my_recording" filename="myrecording.jfr" compress=false (running)
$

例2-4 -XX:-UnlockCommercialFeaturesによる商用機能のロック

例2-4では、商用機能を明示的にロックしたまま(-XX:-UnlockCommercialFeatures)アプリケーションを起動します。その後、VM.unlock_commercial_featuresを使用して商用機能をロック解除し、JFR.startを使用して新しいフライト記録を開始します。

$ java -XX:-UnlockCommercialFeatures -jar MyApp.jar

$jcmd 40110 VM.command_line
40110:
VM Arguments:
jvm_args: -XX:-UnlockCommercialFeatures
java_command: MyApp.jar
java_class_path (initial): MyApp.jar
Launcher Type: SUN_STANDARD

$jcmd 40110 VM.check_commercial_features
40110:
Commercial Features are locked.

$jcmd 40110 VM.unlock_commercial_features
40110:
Commercial Features now unlocked.

$jcmd 40110 VM.check_commercial_features
40110:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has not been used.
  Resource Management is disabled.

$jcmd 40110 JFR.start name=my_recording filename=myrecording.jfr dumponexit=true
40110:
Started recording 1. No limit (duration/maxsize/maxage) in use.

Use JFR.dump name=my_recording to copy recording data to file.

$jcmd 40110 JFR.check
40110:
Recording: recording=1 name="my_recording" filename="myrecording.jfr" compress=false (running)

$jcmd 40110 VM.check_commercial_features
40110:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder has been used.
  Resource Management is disabled.$

例2-5 -XX:-FlightRecorderによるJFRの無効化

例2-5では、JFRを完全に無効化するために、アプリケーションの起動時にjavaコマンドに-XX:-FlightRecorderを渡します。このオプションが指定されている場合、新しいフライト記録を動的に作成することはできません。

$java -XX:+UnlockCommercialFeatures -XX:-FlightRecorder -jar MyApp.jar
$jcmd 39589 VM.command_line
39589:
VM Arguments:
jvm_args: -XX:+UnlockCommercialFeatures -XX:-FlightRecorder 
java_command: MyApp.jar
java_class_path (initial): MyApp.jar
Launcher Type: SUN_STANDARD

$jcmd 39589 VM.check_commercial_features

39589:
Commercial Features are unlocked.
Status of individual features:
  Java Flight Recorder is disabled.
  Resource Management is disabled.

$jcmd 39589 JFR.check
39589:
Java Flight Recorder is disabled.

$jcmd 39589 JFR.stop
39589:
Java Flight Recorder is disabled.

$jcmd 39589 VM.unlock_commercial_features
39589:
Commercial Features already unlocked.

$jcmd 39589 JFR.start name=my_recording filename=myrecording.jfr dumponexit=true
39589:
Java Flight Recorder is disabled.
$

例2-6 無効なオプションの組合せ

例2-6は、無効なオプションの組合せがjavaコマンドに渡された場合に何が起こるかを示しています。この場合、ユーザーは、商用機能をロックしながら(-XX:-UnlockCommercialFeatures) JFRを有効化しようとしています(-XX:+FlightRecorder)。

$ java -XX:-UnlockCommercialFeatures -XX:+FlightRecorder -jar MyApp.jar
Error: To use 'FlightRecorder', first unlock using -XX:+UnlockCommercialFeatures.
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
$