This page describes how to configure and use object instance tracking for Java applications. For more information about why you may need to configure this, see Java Memory Thrash.
When object instance tracking is enabled, AppDynamics tracks the top 20 application and top 20 system (core Java) classes in the heap by default. You can also track specific classes.
Enabling object instance tracking increases the amount of information captured by the agents, resulting in additional overhead. AppDynamics recommends using object instance tracking only while troubleshooting potential memory leaks. It does not normally need to be enabled during normal operation.
AppDynamics does not perform allocation tracking for core Java classes by default since doing so would add significant system overhead. However, it is possible to track core classes on a short-term basis (for example, while troubleshooting) or in pre-production environments. For more information, see Enabling Allocation Tracking for Core Java Classes.
To enable or disable object instance tracking, you need the Configure Agent Properties permission.
To configure the custom classes to track, you need the Configure Memory Monitoring permission.
For information on AppDynamics Role Based Access Control, see Roles and Permissions.
JRE_HOME>/lib/extand restart the JVM. You can find
JAVA_HOME>/lib/tools.jar. For Java 9 onwards JEP220 moved the capabilities needed by OIT to the Core Java runtime, meaning
tools.jaris no longer necessary.
jdk.jcmd is now no longer a required module for the custom runtime. However, it is required for the proper functioning of object instance tracking.
When using the JDK runtime environment, set the classpath using the
-classpath option for the application. For example:
java -classpath <complete-path-to-tools.jar>;%CLASSPATH% -jar myApp.jar
java -Xbootclasspath/a:<complete-path-to-tools.jar> -jar myApp.jar
To start an object instance tracking session, follow these steps:
Tracked classes now appear in the Object Instance Tracking table. You can drill down to the tracked classes to see details.
For performance reasons, only the top 20 application classes and the top 20 system (core Java) classes in the heap are tracked automatically.
Use the Configure Custom Classes to Track option on the Object Instance Tracking subtab to specify instances of specific classes to track. Note that the classes you configure here are tracked only if their instance count is among the top 1000 instance counts in the JVM.
To track instances of custom classes:
The class you added is now tracked during object instance tracking sessions.