This blog post intends to give some insight into what the monitoring and diagnostics tool Oracle Java Mission Control (JMC) is and how it can be used to investigate Java application performance. There is already a lot of very good writings available about this subject like this or this one. This post aims to be more practical presentation. In this post we’ll be connecting JMC to instance of SampleConsoleServer running on a remote host. Then we will log some runtime data with Java Flight Recorder and analyze it with Java Mission Control.
Note that Java Mission Control is free for use during development and testing but requires a license when used for production purposes.
What is Oracle Java Mission Control?
Oracle Java Mission Control is a tool suite for managing, monitoring, profiling, and troubleshooting your Java applications. Oracle Java Mission Control has been included in standard Java SDK since version 7u40. JMC consists of the JMX Console and the Java Flight Recorder. More plug-ins can easily be installed from within Mission Control. JMC can also be installed in Eclipse IDE.
Java Mission Control uses JMX to communicate with remote Java processes. The JMX Console is a tool for monitoring and managing a running JVM instance. The tool presents live data about memory and CPU usage, garbage collections, thread activity, and more. It also includes a fully featured JMX MBean browser that you can use to monitor and manage MBeans in the JVM and in your Java application.
To enable the remote management agent on a Java process we’ll add the following parameters when starting it:
-Dcom.sun.management.jmxremote=true -Dcom.sun.management.jmxremote.port=3614 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false
Locally these options aren’t needed but in this example we’re going to run SampleConsoleServer on a remote testserver. Also note that screenshot below illustrates Eclipse’s “Run Configurations -> Arguments” tab.
Set VM arguments to enable remote management.
Now when the SampleConsoleServer is started it will allow JMX connections to port 3614. Port number was assigned randomly based on current date.
JMC is bundled together with JDK and can be found from “C:\Program Files\Java\jdk1.x.x_xx\bin\jmc.exe” on Windows machines.
Select “Create a new custom JVM connection”.
Enter Hostname/IP-address and port information and click Finish.
A picture of “Overview”-tab.
Monitor your Java application through MBeans in the MBean Browser.
Define rules to trigger alerts on changes in MBean values.
The tabbed pages provide runtime information about system properties, memory management, Java threads and more.
Java Flight Recorder
Java Flight Recorder is a profiling and event collection framework built into the Oracle JDK. Java Flight Recorder can be used to collect recordings without using JMC, but in this example we will be using these tools together.
The application which is to be analyzed must always be started with options
-XX:+UnlockCommercialFeatures -XX:+FlightRecorder
More VM arguments added before starting SampleConsoleServer.
We’ll also run a script connecting UaClients, reading values from the SampleConsoleServer and disconnecting UaClients to get somewhat of a interesting dataset generated.
Flight Recording settings can be opened by double-clicking the “Flight Recorder” icon in the JMV Browser.
Flight recording settings.
There are two alternative recording types: fixed recordings and continuous recordings. Continuous recordings have no end time defined and they must be explicitly dumped.
After clicking “Finish”, the lower edge of the screen will show the recording progress. In this example we will use fixed time recording and run the flight recording for 1 minute. After the recording finishes, the results can be analyzed with JMC.
The “General” tab of flight recording looks like this:
The Java Flight Recorder provides information about the operating system, the JVM and the Java application running in the JVM.
It is clearly visible from the CPU usage spikes that the script has connected and disconnected set of clients five times during the one minute time period of flight recording. Also in the beginning of recording last batch of previous clients were just about to disconnect from server.
Next we move on to the “Code” tab:
Code tab
This tab shows us activity of different Packages and Classes. We can deduct that java.util.concurrent has been the most used Package during this execution and org.opcfoundation.us.builtintype.NodeId is the most used Class.
Let’s move on to the “Hot Methods” tab in the bottom of the screen:
Hot Methods tab
This view shows us the activity of specific methods and the origin from where these methods have been called. We can see that “org.opcfoundation.ua.builtintypes.NodeId.compareTo(NodeId)” consumed the most time in our execution setting.
Conclusion
This was a short introduction to using Java Mission Control and Flight Recorder. In a coming post we’ll be looking into declaring our own MBeans and MXBeans which can be viewed with a MBean browser. We’ll also make an example OPC UA server which publishes runtime data in it’s address space.
Similar tools to look into:
Java Mission Control is one of many performance monitoring and diagnostics tools available for the Java platform.