在Neo4j桌面上启用Java飞行记录器

Question

我试图使Java Flight Recorder能够在使用Neo4j桌面运行Cypher查询时每10秒收集一次线程转储。但在Neo4j桌面的“设置”选项卡（配置文件）中，建议的飞行记录器选项无法识别，并在启动过程中引发错误。

我正在使用Oracle JDK 11。

这些是我在文件中输入的命令-

# flight recorder settings
dbms.jvm.additional=-XX:+UnlockCommercialFeatures
dbms.jvm.additional=-XX:+FlightRecorder
dbms.jvm.additional=-XX:FlightRecorderOptions=stackdepth=500
dbms.jvm.additional=-XX:+UnlockDiagnosticVMOptions
dbms.jvm.additional=-XX:+DebugNonSafepoints

当我启动DB时，这些会引发一个错误-

Active database: graph.db
Directories in use:
  home:         /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3
  config:       /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/conf
  logs:         /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/logs
  plugins:      /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/plugins
  import:       /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/import
  data:         /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/data
  certificates: /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/certificates
  run:          /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/run
Starting Neo4j.
Unrecognized VM option 'UnlockCommercialFeatures'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.
Active database: graph.db
Directories in use:
  home:         /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3
  config:       /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/conf
  logs:         /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/logs
  plugins:      /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/plugins
  import:       /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/import
  data:         /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/data
  certificates: /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/certificates
  run:          /Users/manishgiri/Library/Application Support/Neo4j Desktop/Application/neo4jDatabases/database-4efa4b3e-50bc-46fa-90b2-ee6df8205205/installation-3.5.3/run
Starting Neo4j.
Unrecognized VM option 'FlightRecorder'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

通过在另一个简单的程序上测试，我已经验证了飞行记录器在我的机器上工作-

java -XX:+UnlockCommercialFeatures -XX:+FlightRecorder -XX:StartFlightRecording=duration=120s,filename=myrecording.jfr OOMEGenerator

此命令工作正常，并成功生成录制。

是否有其他方法在配置文件中启用飞行记录器设置？

Answer 1

Neo4j桌面包括一个来自Azul的Java虚拟机，它基于OpenJDK，不识别-XX:UnlockCommercialFeatures标志。

由于飞行记录器已经开源，因此不再需要该标志（JDK 11）。Oracle JDK将忽略该标志。

最简单的方法就是删除-XX:UnlockCommercialFeatures标志。

如果这不起作用，即它抱怨-XX:FlightRecorder或-XX:StartFlightRecording，可能是因为Neo4j Desktop附带了Azul的早期版本，Azul不支持FlightRecorder。

如果是这种情况，您必须切换JDK。

（您也可以删除-XX： FlightRecorder，因为自Oracle JDK 8u40之前的版本以来不需要此标志）