Tuesday, January 24, 2012

Monitoring Remote JVMs Using JVisualVM


Real-time monitoring of a SOA/ADF 11g server Sun JVM can be provided by several tools. Many of you must have used or heard about Java VisualVM tool. VisualVM is a tool that provides a visual interface for viewing detailed information about Java applications while they are running on a Sun Java Virtual Machine (for JRockit we would use JRockit Mission Control). VisualVM has features of use to application developers, system administrators, quality engineers and application users. Below are some of its key functions and features.
§  Display local and remote Java applications.
§  Display application configuration and runtime environment.(You can see the JVM startup parameters and properties)
§  Monitor application memory consumption and runtime behavior(Heap/Non Heap usage and GC Info)
§  Monitor application threads.(Displays number of threads in JVM, their status ie Running, Sleeping, Inactive, Deadlock)
§  Profile application performance or analyze memory allocation (Used to troubleshoot Memory Leak and OOM Issues)
§  Take and display thread dumps (Can be used to troubleshoot performance issues)
§  Take and browse heap dumps.(Used for troubleshooting Memory Leaks)
§  Analyze core dumps and applications offline.

This tool is available in the HotSpot JDK installation $HotSpot_JDK_INSTALL/bin. It is started by running the jvisualvm executable. JVisualVM can be run either on the same machine on which the SOA/ADF server runs or on a separate machine from the SOA runtime server.

Monitoring Local JVMs using JVisualVM:
If you are running JVisualVM on the same machine, on which SOA/ADF JVM runs, the setup is quite simple and straight forward. You simply have to go to the $JAVA_HOME/bin and run the jvisualvm executable. As shown below under the Local icon you can find the local JVM process PIDs and the needed information. Double click on any one of the  processes under Local icon and on the right hand side of the screen you would be able to see the desired information (described later)


Monitoring Remote  JVMs using JVisualVM:
If running JVisualVM from a remote machine, i.e. a JDK that is remote to the SOA Managed Server you will need to configure a JMX port in the JVM startup parameters in order to monitor the SOA/ADF server JVM. Below are the steps:


1. Configure a JMX port.
Add the below  -Dcom.sun.management.jmxremote parameters to the SOA/ADF Managed Server JVM startup parameters.Keep in mind that you only want to define this for a specific server in the domain since reuse of the JMX port number between servers will not be allowed. For example if you want to monitor the JVM on soa_server1 you could add the following to its JVM startup parameters:

-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=8500 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Djavax.management.builder.initial=weblogic.management.jmx.mbeanserver.WLSMBeanServerBuilder

So after adding the above parameters the JVM startup parameters would look like:

-server -d64 -Xss256k -Xms1g -Xmx1g-XX:NewRatio=2 -XX:+AggressiveOpts -XX:PermSize=512m -XX:MaxPermSize=512m -XX:+UseParallelGC -XX:+UseParallelOldGC -XX:ParallelGCThreads=16 -XX:InitialSurvivorRatio=10 -XX:SurvivorRatio=10 -Dweblogic.management.discover=false -Dweblogic.StuckThreadMaxTime=900 -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/tmp/soa_server1_gc.hprof -verbose:gc -Xloggc:/tmp/soa_server1_gc.log -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=8500 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Djavax.management.builder.initial=weblogic.management.jmx.mbeanserver.WLSMBeanServerBuilder



2. Restart the SOA/ADF Managed Server (The JVM parameters of which were modified in Step 1)
3. Download and install JVisualVM from here on your local machine.
4. Open the Command Prompt on your Local Machine and navigate to the JAVA_HOME/bin as shown below. Enter the command as shown. You can also pass JVM parameters after a -J, for example to set the maximum PermSize to 256MB:


The JVisualVM Console:



5. Install All of the Available Plug-ins Select Tools -> Plugins download and install all of the available plugins, this will give additional display tabs once connected to a JVM. Restart JVisualVM, going back into Tools -> Plugins -> Installed Tab should show all of the installed plug-in:


6. Create a Remote Connection if Running JVisualVM Remotely from the SOA Server
    Select the Add Remote Host icon:




7. Enter the Hostname of the server on which the SOA/ADF managed server is running. Display name can be anything related to the physical server. I chose it to be TEST_ADF_Server)


8. Right click on Test_ADF_Server under Remote icon and click on Add JMX Connection.

9. After the : in the Connection field enter the defined JMX port of 8500, this is from Dcom.sun.management.jmxremote.port=8500 also check the Display name box(Can be the JVM name):Click OK




10. After few seconds you should find the Display name(You specified in the previous step under the TEST_ADF_Server icon.

11. Right Click and click on Open. On the right hand side page you should find the JVM details as shown below.

Hurray !! You are now connected to the remote JVM via your local JVisualVM.

You can explore all of the tabs provided, these seem to be the most useful:Some of them are mentioned below:

1. The Monitor tab: 
    Provides the following graphs of the running system:


Also there is a Perform GC button to force a garbage collection and a Heap Dump button to cause a heap dump. The resulting heap dump will be eventually loaded into JVisualVM in a new tab where it can be analyzed. The loading may be slow and perhaps not as detailed as one would like. It may be a better idea to take heap dumps from the command line from the JDK installation where the SOA server is running:



The Threads tab:


The VisualGC Tab:

It might report you the below issue(Not Supported for the JVM)


This issue occurs when there is a version mismatch between You will get this if the JDK running JVisualVM and the SOA server are not the same version or if the operating systems do not matchMake sure you use the same version of JDKs.

This tab provides a visual representation of the memory Spaces being used in real-time in the PermGen, Old Gen, Eden Space, and Survivor Spaces (S0 & S1). This gives an idea of how how full each partition is at any given time. You can use this to scale the defined memory for the spaces based on actual load.The Graphs section also provides information on the maximum and current sizes of the spaces and their garbage collection statistics.

Conclusion

So in the post I basically have shown how would you use JVisualVM to connect to remote as well as local SOA ADF JVMs. Hope this post was helpful. I havent covered the basics and functions of jvisual vm in detail as there are too many posts already. You can find Oracle documentation here


When it comes to SOA Heap dumps, the heap dumps generated might grow very large.The Heap Dump analysing part in jvisualvm might not work well on large jvms(greater than 3 GB). For such JVM heap analysis I would suggest you take manual dumps using jmat and analyse the dump using eclipse memory analyser. I am currently trying this in my lab and will post my updates soon.


References


  1. jvisualvm - Java Virtual Machine Monitoring, Troubleshooting, and Profiling Tool http://docs.oracle.com/javase/6/docs/technotes/tools/share/jvisualvm.html
  2. VisualVM - http://en.wikipedia.org/wiki/VisualVM
  3. VisualVM Home page - http://visualvm.java.net/


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