AppPerfect Java Profiler

Tutorial : Monitor Contention Detection.

This tutorial provides instructions on how to use AppPerfect Java Profiler product for detecting monitor contention and possible race conditions in a java application. This tutorial assumes you have successfully downloaded and installed AppPerfect DevTest4J on your machine with the default options.

This document is divided into following sections

Creating Common Project
AppPerfect Java Profiler

Within each section, multiple exercises are listed. All exercises assume you have installed the product in C:\AppPerfect\DevTest folder and will be referred as DEVTEST_HOME henceforth in tutorial. If you have installed the product in some other folder, modify the instructions below appropriately.

For this tutorial, create a java file called 'MonitorContention.java' copy-pasting the code shown below and compile it.

import java.io.*;

public class MonitorContention
{
    private static final int queue_size = 1000;
    private Object[]  queue = new Object[ queue_size ];
    private int       head  = 0;
    private int       tail  = 0;

    public synchronized void  enqueue( Object item )
    {
        head %= queue_size;
        queue[++(head)]= item;
        this.notify();                  // The "this" is there only to
    }                                   // improve readability.
    public synchronized Object  dequeue( )
    {
        try
        {
            if( head == tail ) // <=== This is a bug
            {
                long startTime = System.currentTimeMillis();
                System.out.println("waiting...");
                this.wait();
                System.out.println("waiting... time=" + (System.currentTimeMillis() - startTime)/1000);
            }
        }
        catch( InterruptedException e )
        {
            // If we get here, we were not actually notified.
            // returning null does not indicate that the
            // queue is empty, only that the waiting was
            // abandoned.
            return null;
        }
        tail %= queue_size;
        return queue[++(tail) ];
    }

    public static void main(String[] args) throws Exception
    {
        MonitorContention contention = new MonitorContention();
        InputStreamReader console = new InputStreamReader(System.in);
        Thread.sleep(2000);
        createMonitorContentionThread(contention, 8).start();
        createMonitorContentionThread(contention, 12).start();
        Thread.sleep(5000);
        System.out.println("Release ONE");
        createReleaseThread(contention, 2).start();
        Thread.sleep(9000);
        System.out.println("Release TWO");
        createReleaseThread(contention, 2 + 8 + 12).start();
        System.out.print("Press any key to continue...");
        console.read();
        console.read();
    }
    static int count = 0;
    public static Thread createMonitorContentionThread(final MonitorContention contention, final int enqueCount)
    {
        final int th_id = count++;
        return new Thread(new Runnable()
        {
            public void run()
            {
                try
                {
                    for(int i = 0; i < 2 + (enqueCount/2); ++i)
                    {
                        contention.enqueue(new Object());
                    }
                    System.out.println("Waiting for 5 sec. [" + th_id + "]");
                    for(int i = 0; i < enqueCount; ++i)
                    {
                        contention.dequeue();
                        System.out.println("Waiting for 0.1 sec. [" + th_id + "]");
                        Thread.sleep(100);
                    }
                }
                catch(Exception ex)
                {
                    ex.printStackTrace();
                }
            }
        });
    }

    public static Thread createReleaseThread(final MonitorContention contention, final int dequeCount)
    {
        final int th_id = count++;
        return new Thread(new Runnable()
        {
            public void run()
            {
                try
                {
                    for(int i = 0; i < dequeCount; ++i)
                    {
                        contention.enqueue(new Object());
                    }
                }
                catch(Exception ex)
                {
                    ex.printStackTrace();
                }
            }
        });
    }
}

Creating Common Project

Exercise 1: Launch AppPerfect DevTest4J

Action:

Click on Start -> Programs ->AppPerfect DevTest4J x.x.x -> AppPerfect DevTest4J
On launching AppPerfect DevTest4J a Welcome page will be displayed. Go through the brief description given for each product and click on the product icon to view its perspective.
NB: Welcome page is displayed only when DevTest4J x.x.x is launched and last time no project was opened.
To switch between different product perspectives click on corresponding project button in toolsbar.

Exercise 2: Creating a Common Project

Action:

Launch the Common Project Wizard by clicking File ->New... menu option. The New Project wizard will be launched.
Go through the instruction provided on top of the General tab.
Keep the default project name and location for the purpose of this exercise. We don't have to provide "Notification" settings or "Remote Application/AppServer" settings for this exercise. Click on the Next button.
In the Source tab provide the location of source file "RaceCondition.java". Click the Next button.
Use the default JDK which is bundled with AppPerfect DevTest4J and click on the Next button.
In the "Environment" tab provide the location of "RaceCondition.class" file.
Click on "Verify Classpath" button to validate the classpath.
Classpath validation dialog will be launched and the classpath will be verified. A message saying that the classpath specified is correct should be displayed. Click on the "OK" button. Click on the Next button.
In the "Target" tab select project type as "LOCAL".
For working folder provide the path to the folder containing the the "RaceCondition.class" file.
Specify the Main Class as "RaceCondition".
Select the "Launch target application automatically" checkbox. Click on the Finish button.
A confirmation message saying that the project is saved will be displayed. Click on the OK button.