Let Me Count The Ways – Various methods of generating stack dump for JVM in production

As I profiled previously thread dumps in Java are essential in diagnosing production issues with high CPU, locking, threading deadlocks, etc. There are great online thread dump analysis tools such as http://fastthread.io/ that can analyze and spot problems. But to those tools you need provide proper thread dumps as input. I already blogged about many tools to do so in the past like jstack, JvisualVM and Java Mission Control. Here I will try to summarize all of the ways to capture usable thread dumps in production Java application:

  • JStack

JStack remains one of the most common ways to capture thread dumps. It’s a command ike utility bundled in JDK. The Jstack tool is shipped in JDK_HOME\bin folder. Here is the command that you need to issue to capture thread dump:

jstack -l   > 

Where

pid: is the Process Id of the application, whose thread dump should be captured

file-path: is the file path where thread dump will be written in to.

Example here:

jstack -l 37321 > /opt/tmp/threadDump.txt

As per the example thread dump of the process would be generated in /opt/tmp/threadDump.txt file.

    • Kill –3

 

In many customers only JREs are installed in production machines. Since jstack and other tools are only part of JDK, you wouldn’t be able to use jstack. In such circumstances, ‘kill -3’ option can be used.

kill -3 

Where:

pid: is the Process Id of the application, whose thread dump should be captured

Example:</P?

 Kill -3 37321

When ‘kill -3’ option is used thread dump is sent to standard error stream. Fpr example in apps running under Tomcat it will be <TOMCAT_HOME>/logs/catalina.out file. VisualVM Java VisualVM is a graphical user interface tool that provides detailed information about the applications while they are running on a specified Java Virtual Machine (JVM). It’s located in JDK_HOME\bin\jvisualvm.exe. It’s part of Sun\Oracle JDK distribution since JDK 6 update 7.s Launch the jvisualvm. On the left panel, you will notice all the java applications that are running on your machine. You need to select your application from the list (see the red color highlight in the below diagram). This tool also has the capability to capture thread dumps from the java processes that are running in remote host as well. vjvm In order to generate thread dump, go to Threads Tab and click on Thread Dump button.

    •   Java Mission Control

 

Java Mission Control (JMC) is a tool that collects and analyze data from Java applications running locally or deployed in production environments. This tool has been packaged into JDK since Oracle JDK 7 Update 40. This tool also provides an option to take thread dumps from the JVM. JMC tool is present in JDK_HOME\bin\jmc.exe Once you launch the tool, you will see all the Java processes that are running on your local hostAs you use Flight Recorder feature on one of these processes , in the “Thread Dump” field, you can select the interval in which you want to capture thread dump. jmc

    • ThreadMXBean

 

Introduced in JDK 1.5, ThreadMXBean is a management interface for thread system in JVM and allows you to create thread dump in few lines of code in application like below:

Example

public void  dumpThreadDump() {



        ThreadMXBean threadMxBean = ManagementFactory.getThreadMXBean();



        for (ThreadInfo ti : threadMxBean.dumpAllThreads(true, true)) {



            System.out.print(ti.toString());

threadmxbean

 

  • JCMD

The jcmd tool was introduced with Oracle’s Java 7. It’s useful in troubleshooting issues with JVM applications. It has various capabilities such as identifying java process Ids, acquiring heap dumps, acquiring thread dumps, acquiring garbage collection statistics, ….

Using the below JCMD command you can generate thread dump:

jcmd  Thread.print > 

where

pid: is the Process Id of the application, whose thread dump should be captured

file-path: is the file path where thread dump will be written in to.

Example

jcmd 37321 Thread.print > /opt/tmp/threadDump.txt

For more see – https://docs.oracle.com/javase/7/docs/technotes/tools/windows/jcmd.html, https://blogs.oracle.com/jmxetc/entry/threadmxbean_a_singleton_mxbean_for , http://www.javamex.com/tutorials/profiling/profiling_java5_threads_howto.shtml , http://blog.takipi.com/oracle-java-mission-control-the-ultimate-guide/ , https://www.prosysopc.com/blog/using-java-mission-control-for-performance-monitoring/

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