Talk about the OpenJDK JHSDB tool

sequence

This article focuses on the JHSDB tool of openJDK

sa-jdi.jar

export JAVA_HOME="/ Library/Java/JavaVirtualMachines jdk1.8.0 _151. JDK/Contents/Home"
chmod +x $JAVA_HOME/lib/sa-jdi.jar
java -cp $JAVA_HOME/lib/sa-jdi.jar sun.jvm.hotspot.HSDB
java -cp $JAVA_HOME/lib/sa-jdi.jar sun.jvm.hotspot.CLHSDB
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Before Java9, there was a sa-jdi.jar in the JAVA_HOME/lib directory that could be used to start HSDB(The graphical interface) and CLHSDB (The command line)
The full name of THE SA in SA-jdi. jar is ras Agent, which is a component provided by Sun to help debug HotSpot. HSDB is ras Agent
HSDB is short for HotSpot Debugger. The Serviceability Agent performs a batch of batch attaching, snapshot suspending, and deattaching.Process recovery), so be careful when using HSDB

jhsdb

/ # jhsdb
    clhsdb       	command line debugger
    debugd       	debug server
    hsdb         	ui debugger
    jstack --help	to get more information
    jmap   --help	to get more information
    jinfo  --help	to get more information
    jsnap  --help	to get more information
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JHSDB is introduced in Java9 and can be found in the JAVA_HOME/bin directory. It replaces the previous JAVA_HOME/lib/sa-jdi.jar for JDk9
JHSDB has CLHSDB, DEBUGD, HSDB, jSTACK, JMAP, jinfo, and jSNAP modes
HSDB is the UI debugger, which is the same as sun.jvm.hotspot.hsdb before JDK9. CLHSDB is sun.Jvm.hotspot.clhsdb before JDK9

jhsdb jstack

/ # jhsdb jstack --help
    --locks	to print java.util.concurrent locks
    --mixed	to print both java and native frames (mixed mode)
    --exe	executable image name
    --core	path to coredump
    --pid	pid of process to attach
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–pid specifies the process ID of the JVM. –exe specifies the executable file; –core specifies the core dump file

abnormal

jhsdb jstack --mixed --pid 1
//......
Caused by: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed fora lwp at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.getThreadIntegerRegisterSet0(Native Method)  at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$1GetThreadIntegerRegisterSetTask.doit(LinuxDebuggerLocal.java:534)
	at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.run(LinuxDebuggerLocal.java:151)
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If this exception is a JDK version problem, try another JDK build

debugger

/ # jhsdb jstack --locks --pid 1
Attaching to process ID 1, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 12+33
Deadlock Detection:

No deadlocks found.

"DestroyJavaVM" #32 prio=5 tid=0x000055c3b5be0800 nid=0x6 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
   JavaThread state: _thread_blocked

Locked ownable synchronizers:
    - None

"http-nio-8080-Acceptor-0" #30 daemon prio=5 tid=0x000055c3b5d71800 nid=0x2f runnable [0x00007fa0d13de000]
   java.lang.Thread.State: RUNNABLE
   JavaThread state: _thread_in_native
 - sun.nio.ch.ServerSocketChannelImpl.accept0(java.io.FileDescriptor, java.io.FileDescriptor, java.net.InetSocketAddress[]) @bci=0 (Interpreted frame)
 - sun.nio.ch.ServerSocketChannelImpl.accept(java.io.FileDescriptor, java.io.FileDescriptor, java.net.InetSocketAddress[]) @bci=4, line=525 (Interpreted frame)
 - sun.nio.ch.ServerSocketChannelImpl.accept() @bci=41, line=277 (Interpreted frame)
 - org.apache.tomcat.util.net.NioEndpoint.serverSocketAccept() @bci=4, line=448 (Interpreted frame)
 - org.apache.tomcat.util.net.NioEndpoint.serverSocketAccept() @bci=1, line=70 (Interpreted frame)
 - org.apache.tomcat.util.net.Acceptor.run() @bci=98, line=95 (Interpreted frame)
 - java.lang.Thread.run() @bci=11, line=835 (Interpreted frame)

Locked ownable synchronizers:
    - <0x00000000e3aab6e0>, (a java/util/concurrent/locks/ReentrantLock$NonfairSync)

"http-nio-8080-ClientPoller-0" #29 daemon prio=5 tid=0x000055c3b5c20000 nid=0x2e runnable [0x00007fa0d14df000]
   java.lang.Thread.State: RUNNABLE
   JavaThread state: _thread_in_native
 - sun.nio.ch.EPoll.wait(int, long, int, int) @bci=0 (Interpreted frame)
 - sun.nio.ch.EPollSelectorImpl.doSelect(java.util.function.Consumer, long) @bci=96, line=120 (Interpreted frame)
 - sun.nio.ch.SelectorImpl.lockAndDoSelect(java.util.function.Consumer, long) @bci=42, line=124 (Interpreted frame)
	- locked <0x00000000e392ece8> (a sun.nio.ch.EPollSelectorImpl)
	- locked <0x00000000e392ee38> (a sun.nio.ch.Util$2)
 - sun.nio.ch.SelectorImpl.select(long) @bci=31, line=136 (Interpreted frame)
 - org.apache.tomcat.util.net.NioEndpoint$Poller.run() @bci=55, line=743 (Interpreted frame)
 - java.lang.Thread.run() @bci=11, line=835 (Interpreted frame)

Locked ownable synchronizers:
    - None

"http-nio-8080-exec-10" #28 daemon prio=5 tid=0x000055c3b48d6000 nid=0x2d waiting on condition [0x00007fa0d15e0000]
   java.lang.Thread.State: WAITING (parking)
   JavaThread state: _thread_blocked
 - jdk.internal.misc.Unsafe.park(boolean, long) @bci=0 (Interpreted frame)
	- parking to wait for <0x00000000e3901670> (a java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionObject)
 - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=194 (Interpreted frame)
 - java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await() @bci=42, line=2081 (Interpreted frame)
 - java.util.concurrent.LinkedBlockingQueue.take() @bci=27, line=433 (Interpreted frame)
 - org.apache.tomcat.util.threads.TaskQueue.take() @bci=36, line=107 (Interpreted frame)
 - org.apache.tomcat.util.threads.TaskQueue.take() @bci=1, line=33 (Interpreted frame)
 - java.util.concurrent.ThreadPoolExecutor.getTask() @bci=147, line=1054 (Interpreted frame)
 - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker) @bci=26, line=1114 (Interpreted frame)
 - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=628 (Interpreted frame)
 - org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run() @bci=4, line=61 (Interpreted frame)
 - java.lang.Thread.run() @bci=11, line=835 (Interpreted frame)
 //......

/ # jhsdb jstack --mixed --pid 1
Attaching to process ID 1, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 12+33
Deadlock Detection:

No deadlocks found.

----------------- 47 -----------------
"http-nio-8080-Acceptor-0" #30 daemon prio=5 tid=0x000055c3b5d71800 nid=0x2f runnable [0x00007fa0d13de000]java.lang.Thread.State: RUNNABLE JavaThread state: _thread_in_native 0x00007fa0ee0923ad ???????? -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- and -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --"http-nio-8080-ClientPoller-0" #29 daemon prio=5 tid=0x000055c3b5c20000 nid=0x2e runnable [0x00007fa0d14df000]
   java.lang.Thread.State: RUNNABLE
   JavaThread state: _thread_in_native
0x00007fa0ee05f3d0	epoll_pwait + 0x1d
0x00007fa0daa97810	* sun.nio.ch.EPoll.wait(int, long, int, int) bci:0 (Interpreted frame)
0x00007fa0daa91680	* sun.nio.ch.EPollSelectorImpl.doSelect(java.util.function.Consumer, long) bci:96 line:120 (Interpreted frame)
0x00007fa0db85f57c	* sun.nio.ch.SelectorImpl.lockAndDoSelect(java.util.function.Consumer, long) bci:42 line:124 (Compiled frame)
* sun.nio.ch.SelectorImpl.select(long) bci:31 line:136 (Compiled frame)
* org.apache.tomcat.util.net.NioEndpoint$Poller.run() bci:55 line:743 (Interpreted frame)
0x00007fa0daa91c88	* java.lang.Thread.run() bci:11 line:835 (Interpreted frame)
0x00007fa0daa88849	<StubRoutines>
0x00007fa0ed122952	_ZN9JavaCalls11call_helperEP9JavaValueRK12methodHandleP17JavaCallArgumentsP6Thread + 0x3c2
0x00007fa0ed1208d0	_ZN9JavaCalls12call_virtualEP9JavaValue6HandleP5KlassP6SymbolS6_P6Thread + 0x200
0x00007fa0ed1ccfc5	_ZL12thread_entryP10JavaThreadP6Thread + 0x75
0x00007fa0ed74f3a3	_ZN10JavaThread17thread_main_innerEv + 0x103
0x00007fa0ed74c3f5	_ZN6Thread8call_runEv + 0x75
0x00007fa0ed4a477e	_ZL19thread_native_entryP6Thread + 0xee
//......
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— LOCKS or –mixed can take a long time (a few minutes, possibly up to 6 minutes), and therefore the process can be paused for a long time, so be careful when using these two options

jhsdb jmap

jmap -heap pid

/ # jmap -heap 1
Error: -heap option used
Cannot connect to core dump or remote debug server. Use jhsdb jmap instead
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Symptom When the jmap-heap pid command is used in jdk9 or later to view the current heap usage, an error message is displayed indicating that JHSDB jmap is used instead

jhsdb jmap pid

/ # jhsdb jmap 1
sh: jhsdb: not found
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JHSDB = JHSDB = JHSDB = JHSDB = JHSDB = JHSDB = JHSDB = JHSDB

PTRACE_ATTACH failed

/ # jhsdb jmap 1
You have to set --pid or --exe.
    <no option>	to print same info as Solaris pmap
    --heap	to print java heap summary
    --binaryheap	to dump java heap in hprof binary format
    --dumpfile	name of the dump file
    --histo	to print histogram of java object heap
    --clstats	to print class loader statistics
    --finalizerinfo	to printinformation on objects awaiting finalization --exe executable image name --core path to coredump --pid pid of process to  attach /# jhsdb jmap --heap --pid 1
Attaching to process ID 1, please wait...
ERROR: ptrace(PTRACE_ATTACH, ..) failed for 1: Operation not permitted
Error attaching to process: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process: ptrace(PTRACE_ATTACH, ..) failed for 1: Operation not permitted
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process: ptrace(PTRACE_ATTACH, ..) failed for 1: Operation not permitted
	at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.execute(LinuxDebuggerLocal.java:176)
	at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach(LinuxDebuggerLocal.java:336)
	at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attachDebugger(HotSpotAgent.java:672)
	at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebuggerLinux(HotSpotAgent.java:612)
	at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.setupDebugger(HotSpotAgent.java:338)
	at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.go(HotSpotAgent.java:305)
	at jdk.hotspot.agent/sun.jvm.hotspot.HotSpotAgent.attach(HotSpotAgent.java:141)
	at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.start(Tool.java:185)
	at jdk.hotspot.agent/sun.jvm.hotspot.tools.Tool.execute(Tool.java:118)
	at jdk.hotspot.agent/sun.jvm.hotspot.tools.JMap.main(JMap.java:176)
	at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runJMAP(SALauncher.java:326)
	at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:455)
Caused by: sun.jvm.hotspot.debugger.DebuggerException: Can't attach to the process: ptrace(PTRACE_ATTACH, ..) failed for 1: Operation not permitted at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.attach0(Native Method) at  jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$1AttachTask.doit(LinuxDebuggerLocal.java:326) at jdk.hotspot.agent/sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.run(LinuxDebuggerLoca l.java:151)Copy the code

PTRACE_ATTACH is disabled by Docker and needs to be enabled when running containers

Docker enable SYS_PTRACE

docker run --cap-add=SYS_PTRACE
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Then you can use JHSDB normally as follows:

/ # jhsdb jmap --heap --pid 1
Attaching to process ID 1, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 12+33

using thread-local object allocation.
Shenandoah GC with 4 thread(s)

Heap Configuration:
   MinHeapFreeRatio         = 40
   MaxHeapFreeRatio         = 70
   MaxHeapSize              = 523763712 (499.5MB)
   NewSize                  = 1363144 (1.2999954223632812MB)
   MaxNewSize               = 17592186044415 MB
   OldSize                  = 5452592 (5.1999969482421875MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   ShenandoahRegionSize     = 262144 (0.25MB)

Heap Usage:
Shenandoah Heap:
   regions   = 1997
   capacity  = 523501568 (499.25MB)
   used      = 70470552 (67.2059555053711MB)
   committed = 144441344 (137.75MB)
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jhsdb jinfo

/ # jhsdb jinfo --help
    --flags	to print VM flags
    --sysprops	to print Java System properties
    <no option>	to print both of the above
    --exe	executable image name
    --core	path to coredump
    --pid	pid of process to attach
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To display the sysprops of jinfo using JHSDB:

/ # jhsdb jinfo --sysprops --pid 1
Attaching to process ID 1, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 12+33
awt.toolkit = sun.awt.X11.XToolkit
java.specification.version = 12
sun.jnu.encoding = UTF-8
//......
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This command is equivalent to jinfo-sysprops 1

jhsdb jsnap

/ # jhsdb jsnap --pid 1
Attaching to process ID 1, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 12+33
java.threads.started=27 event(s)
java.threads.live=24
java.threads.livePeak=24
java.threads.daemon=20
java.cls.loadedClasses=8250 event(s)
java.cls.unloadedClasses=1 event(s)
java.cls.sharedLoadedClasses=0 event(s)
java.cls.sharedUnloadedClasses=0 event(s)
java.ci.totalTime=18236958158 tick(s)
java.property.java.vm.specification.version=12
java.property.java.vm.specification.name=Java Virtual Machine Specification
java.property.java.vm.specification.vendor=Oracle Corporation
java.property.java.vm.version=12+33
java.property.java.vm.name=OpenJDK 64-Bit Server VM
java.property.java.vm.vendor=Azul Systems, Inc.
java.property.java.vm.info=mixed mode
java.property.jdk.debug=release
//......
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JHSDB jsnap function mainly by the JDK. Hotspot. The agent module in the sun. The JVM. Hotspot. View jsnap. Java to provide, Class loading/ semantics can be used to view threads and class loading/ semantics events, JVM property parameters, etc. –all shows more JVM property parameters

JHSDB and JCMD

JHSDB: A New Tool for JDK 9 JHSDB: A New Tool for JDK 9

summary

Before Java9, there was a sa-jdi.jar in the JAVA_HOME/lib directory that could be used to start HSDB(The graphical interface) and CLHSDB (The command line); The 100ras Agent, the full name of SA in SA-jdi. jar, is a Component that Sun has provided to help debug HotSpot. HSDB has 100ras Agent. HSDB is short for HotSpot Debugger. The Serviceability Agent performs a batch of batch attaching, snapshot suspending, and deattaching.Process recovery), so be careful when using HSDB
JHSDB is introduced in Java9 and can be found in the JAVA_HOME/bin directory. It replaces JAVA_HOME/lib/sa-jdi.jar before jdk9; JHSDB has CLHSDB, DEBUGD, HSDB, jSTACK, JMAP, jinfo, and jSNAP modes. HSDB is the UI debugger, which is the same as sun.jvm.hotspot.hsdb before JDK9. CLHSDB is sun.Jvm.hotspot.clhsdb before JDK9
JHSDB is in the jdk.hotspot. Agent module; For JHSDB jStack –locks or –mixed commands can take a long time (A few minutes, maybe nearly six minutes), so the process may be suspended for a long time. Be careful when using these options; For jdk9 and later versions, JHSDB jmap –heap –pid is used instead of using the jmap-heap command to query heap memory. Using JHSDB Jmap requires that PTRACE_ATTACH be enabled when the container is run

doc

JVM Information Viewing
jhsdb
jdk.hotspot.agent jhsdb
jhsdb: A New Tool for JDK 9
jcmd: One JDK Command-Line Tool to Rule Them All
JVM in Docker and PTRACE_ATTACH
Serviceability in HotSpot
The HotSpot™ Serviceability Agent: An out-of-process high level debugger for a Java™ virtual machine

sequence

sa-jdi.jar

jhsdb

jhsdb jstack

abnormal

debugger

jhsdb jmap

jmap -heap pid

jhsdb jmap pid

PTRACE_ATTACH failed

Docker enable SYS_PTRACE

jhsdb jinfo

jhsdb jsnap

JHSDB and JCMD

summary

doc

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