在未成功运行的 JDK-8 java 进程上使用 JDK-11 运行 jcmd

Question

I am trying to monitor native memory of tomcat using jcmd but getting following exception: Command: jcmd 14533<pid of tomcat> VM.native_memory summary

I have installed 2 jdk's jdk-11 AND jdk-8 .

Tomcat is running by jdk-8 and jcmd used jdk-11 then i got following exception:

com.sun.tools.attach.AttachNotSupportedException: Unable to open socket file /proc/31752/root/tmp/.java_pid31752: target process 31752 doesn't respond within 10500ms or HotSpot VM not loaded
    at jdk.attach/sun.tools.attach.VirtualMachineImpl.<init>(VirtualMachineImpl.java:100)
    at jdk.attach/sun.tools.attach.AttachProviderImpl.attachVirtualMachine(AttachProviderImpl.java:58)
    at jdk.attach/com.sun.tools.attach.VirtualMachine.attach(VirtualMachine.java:207)
    at jdk.jcmd/sun.tools.jcmd.JCmd.executeCommandForPid(JCmd.java:114)
    at jdk.jcmd/sun.tools.jcmd.JCmd.main(JCmd.java:98)

I attched -XX:+StartAttachListener with java process but it didn't work.

Answer 1

It can be a user permission issue: jmap has to be run with the same user as the java process. eg if the owner is usera and this is running in a docker contained execute jmap as user usera

docker exec --user usera -it container_id jmap -dump:format=b,file=/home/usera/memorydump.bin 1

Answer 2

If you are running tomcat as a service on linux check following config in unit file ie tomcat.service

1. PrivateTmp=yes, should be removed. As PrivateTmp=yes create private /tmp folder which is not accessible by tool
2. If you have ProtectSystem=strict, add ReadWritePaths=/tmp/

Go through man page for systemd unit file config