It is my blog :) It is not forbidden for me to share off topic pictures huh ?

Me

&

Marc Dacascos

&

Tolga Karadeniz

Reliable Multicasting with JGroups

Append the jgroups jar to your classpath.

Then execute the following code twice in different consoles like this.These are our chat clients.

java -Djava.net.preferIPv4Stack=true SimpleChat


import java.io.*;
import java.net.InetAddress;
import org.jgroups.*;

public class SimpleChat implements Receiver {
    JChannel channel;

    public static void main (String[] args) throws Exception {
        new SimpleChat ().start ();
    }

    private void start () throws Exception {
        channel = new JChannel ();
        channel.connect ("ChatCluster");
        channel.setReceiver (this);
        eventLoop ();
        channel.close ();
    }

    private void eventLoop () {
        BufferedReader in = new BufferedReader (new InputStreamReader (System.in));
        while ( true ) {
            try {
                System.out.print ("> ");
                System.out.flush ();
                String line = in.readLine ().toLowerCase ();
                if (line.startsWith ("quit") || line.startsWith ("exit")) {
                    break;
                }
                line = "[" + this + "] " + line;
                Message msg = new Message (null, null, line);
                channel.send (msg);
            } catch (Exception e) {
                e.printStackTrace ();
            }
        }
    }

    public void receive (Message message) {
        System.out.println ("message = " + new String (message.getBuffer ()));
    }

    public byte[] getState () {
        return new byte[0]; 
    }

    public void setState (byte[] bytes) {
        //To change body of implemented methods use File | Settings | File Templates.
    }

    public void viewAccepted (View view) {
        System.out.println ("view = " + view.toString ());
    }

    public void suspect (Address address) {
        System.out.println ("address = " + address);
    }

    public void block () {

    }
}

There are more fancy examples in there. Like org.jgroups.demos.Draw !

Three ways to make an object thread-safe

There are basically three approaches you can take to make an object such as RGBThread thread-safe:

1. Synchronize critical sections
2. Make it immutable
3. Use a thread-safe wrapper 

design techniques and thread safety

Why worry about thread safety?

Given the structure of the JVM, local variables, method parameters, and return values are inherently "thread-safe." But instance variables and class variables will only be thread-safe if you design your class appropriately

-- Bill Venners

Preventing Memery Locks on the Multi CPU machine

Problem
   Multithreaded apps create new objects at the same time
   New objects are always created in the EDEN space
   During object creation, memory is locked
   On a multi CPU machine (threads run concurrently) there can be contention

Solution
    Allow each thread to have a private piece of the EDEN
    space
Thread Local Allocation Buffer
    -XX:+UseTLAB
    -XX:TLABSize=
    -XX:+ResizeTLAB
    (On by default on multi CPU machines and newer JDK)
Analyse TLAB usage
    -XX:+PrintTLAB
JDK 1.5 and higher (GC ergonomics)
    Dynamic sizing algorithm, tuned to each thread

INSIDE THE JAVA VIRTUAL MACHINE / Filip Hanik