Security and Fault-tolerance in Distributed Systems      ETHZ, Winter 2006/07
Christian Cachin, IBM Zurich Research Lab             www.zurich.ibm.com/cca/


*** BONUS EXERCISE / PROGRAMMING PROJECT ***


GROUP COMMUNICATION USING THE JGROUPS TOOLKIT

The goal of this project is to explore practical group communication 
with the JGroups toolkit, see http://www.jgroups.org/

I recommend you retrieve the latest stable release 2.4.1; it requires
Java 1.4.  Get the source package, unpack it, and change to the top 
directory.

If you have ant installed, run the command
        ant all
It will compile the sources, generate the binary distribution, and
generate the Javadoc.  Without ant, there is a "build.sh/build.bat"
script for the same purpose.

Then you can invoke any of the demos using the command "jgroups.sh"
as follows:
        ./jgroups.sh demos/Draw
        ./jgroups.sh demos/Chat
        ./jgroups.sh demos/ViewDemo 
(It gets only interesting if you run the multiple instances of the 
same demo.)

The "jgroups.sh" script is derived from the JGroups-2.5.0-preview
distribution and can be found on 
  http://www.zurich.ibm.com/~cca/sft06/jgroups/

I recommend to create an empty file named "log4j.properties" to
suppress the annoying warning of the log4j package.


TASKS

Modify the ViewDemo.java example to do the following:

a) Make every group member periodically send a message on the channel,
   for example using Channel.send() and by implementing the MessageListener
   interface.  You can include the identity of the sender in a message
   with

     String str = "Hello from " + channel.getLocalAddress();

   Make the group members print all received views and messages.


b) The ViewDemo example uses UDP and IP multicast for communication.
   This works when all group members are local on the same machine or on
   the same LAN. Experiment with the "TCP" stack and get the application
   running across the Internet.  The documentation for the configuration
   of the communication stack is quite rudimentary; just take the defaults
   in the source.  See the manual for tunneling through firewalls.


c) [Real bonus project, only if you are interested] 

   Starting with ViewDemo.java, implement some form of state
   transfer, such that all group members receive the state/history
   of the previous members when they join.

   JGroups already contains this functionality, see demos/Chat.java,
   but the purpose here is to develop an implementation.