Jcmd: Thread.print: Get thread dumps

‘jcmd’ is a command line tool provided by Java, used to send diagnostic command requests to the JVM.

Open command prompt and run ‘jcmd’.

C:\>jcmd
13828 sun.tools.jcmd.JCmd
5012 HelloWorld
8456

As you see the output of jcmd, it shows the process id and the application name.

Application name	Process Id
HelloWorld	5012
sun.tools.jcmd.JCmd	13828

Use the command ‘jcmd HelloWorld help’ to get list of commands available for HelloWorld application.

C:\>jcmd HelloWorld help
5012:
The following commands are available:
JFR.stop
JFR.start
JFR.dump
JFR.check
VM.native_memory
VM.check_commercial_features
VM.unlock_commercial_features
ManagementAgent.stop
ManagementAgent.start_local
ManagementAgent.start
GC.rotate_log
Thread.print
GC.class_stats
GC.class_histogram
GC.heap_dump
GC.run_finalization
GC.run
VM.uptime
VM.flags
VM.system_properties
VM.command_line
VM.version
Help

As you see there are multiple commands are available to the program ‘HelloWorld’. You can get the help of these command by using following syntax.

Syntax

jcmd {APPLICATION_NAME} help {COMMAND}

Example
jcmd HelloWorld help Thread.print

C:\>jcmd HelloWorld help Thread.print
5012:
Thread.print
Print all threads with stacktraces.

Impact: Medium: Depends on the number of threads.

Permission: java.lang.management.ManagementPermission(monitor)

Syntax : Thread.print [options]

Options: (options must be specified using the <key> or <key>=<value> syntax)
        -l : [optional] print java.util.concurrent locks (BOOLEAN, false)

Get the thread dump using jcmd

Use the below command to get the thread dump.

jcmd PID Thread.print > thread.dump

Example

jcmd 5012 Thread.print > thread.dump

Above command prints all the threads with stack traces associated with process id 5012, to thread.dump file.

In my case, thread.dump file contains below data.

thread.dump

5012:
2018-07-22 19:29:18
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.171-b11 mixed mode):

"DestroyJavaVM" #11 prio=5 os_prio=0 tid=0x0000000004be2800 nid=0x37f4 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Thread-0" #10 prio=5 os_prio=0 tid=0x000000001fccc000 nid=0x4690 waiting on condition [0x000000002034f000]
   java.lang.Thread.State: TIMED_WAITING (sleeping)
	at java.lang.Thread.sleep(Native Method)
	at HelloWorld$1.run(HelloWorld.java:9)

"Service Thread" #9 daemon prio=9 os_prio=0 tid=0x000000001e34d800 nid=0x32f0 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C1 CompilerThread2" #8 daemon prio=9 os_prio=2 tid=0x000000001e2f5000 nid=0x4f54 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread1" #7 daemon prio=9 os_prio=2 tid=0x000000001e2f0000 nid=0x1f08 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"C2 CompilerThread0" #6 daemon prio=9 os_prio=2 tid=0x000000001e2ed000 nid=0x41f8 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000000001e2f9800 nid=0x2ab8 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001e2f8800 nid=0x3570 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE

"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x0000000004cdc800 nid=0x3aec in Object.wait() [0x000000001f64f000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(Native Method)
	- waiting on <0x000000076b508ed0> (a java.lang.ref.ReferenceQueue$Lock)
	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
	- locked <0x000000076b508ed0> (a java.lang.ref.ReferenceQueue$Lock)
	at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)
	at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:212)

"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x0000000004cd3000 nid=0x243c in Object.wait() [0x000000001f54f000]
   java.lang.Thread.State: WAITING (on object monitor)
	at java.lang.Object.wait(Native Method)
	- waiting on <0x000000076b506bf8> (a java.lang.ref.Reference$Lock)
	at java.lang.Object.wait(Object.java:502)
	at java.lang.ref.Reference.tryHandlePending(Reference.java:191)
	- locked <0x000000076b506bf8> (a java.lang.ref.Reference$Lock)
	at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)

"VM Thread" os_prio=2 tid=0x000000001e2b7800 nid=0x39c runnable 

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000000004bf8000 nid=0x160c runnable 

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000000004bfa000 nid=0x4808 runnable 

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000000004bfb800 nid=0x4dcc runnable 

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000000004bfd000 nid=0x5cc runnable 

"VM Periodic Task Thread" os_prio=2 tid=0x000000001e34e000 nid=0x2318 waiting on condition 

JNI global references: 4

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