object-tracker

Tracking object creation in the JVM

Introduction

Object-tracker consists of a JVM agent that modifies your java objects in order to track their creation. This information can then be written to a file for later analysis.

Usage

Download the bundle with dependencies from the download page, and unzip. Add the following arguments to the command line when starting java:

-javaagent:./object-tracker-agent-0.1/object-tracker-agent-0.1.jar
-cp ./object-tracker-agent-0.1/javassist.jar:./object-tracker-agent-0.1/juxtapose-1.0.jar

Opening jconsole, look for the MBean named com.epickrram.tools:type=ObjectInstanceCounter. To write object count data to disk, invoke the dumpObjectCreationCounts method, supplying a target filename.

Object-tracker will write out a csv containing the current snapshot of the tracked object creation counts:

classname,count
com.epickrram.testing.TestObjectTwo,48
com.epickrram.testing.TestObjectOne,24

Configuration

You must specify at least an inclusion filter to tell Object-tracker what classes to track.

Configuration by file

Specify a system property com.epickrram.tool.object-tracker.config.file that points to a properties file with the following entries:

• com.epickrram.tool.object-tracker.config.include Semi-colon separated regexes to specify classes to include (e.g. com.mycompany;com.external.library)

• com.epickrram.tool.object-tracker.config.exclude Semi-colon separated regexes to specify classes to exclude

Configuration by property

For simple regexes, just use the above system property keys to specify a single include/exclude regex.

Caveats

Attempting to monitor creation of any of the JDK classes (i.e. java.lang, java.util) will fail with a nasty exception.

Dependencies

Object-tracker uses:

• juxtapose for MBean management
• javassist for byte-code manipulation