Master-Worker-Pattern

A Java implementation of the Master/Worker Design Pattern using JMS and RMI.

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Steps to use

1. Setup Glassfish.

   1. Install Glassfish.
   2. Run the command asadmin start-domain in the bin folder of Glassfish.
   3. Access the Glassfish console on localhost.
   4. Create a Connection Factory named jms/TestConnectionFactory, and Destination Resources named jms/MasterQueue, jms/WorkerQueue and jms/ResultQueue.

2. Create concrete implementations of Job, Master, and Worker.

   1. doWork() in Job defines the work that needs to be done on each Worker Node. This is the method that will be executed on the Worker once it receives a task.
   2. handleNewJob(job) in Master defines what happens when a Job object is received in the MasterQueue. This is the method that will be executed on the Master once it receives a new Job.
   3. handleResult(object) in Master defines what happens when a Job is executed on the Worker, and the result is placed on the ResultQueue. This is the method that will be executed on the Master once it receives a result on the ResultQueue.
   4. handleNewJob(newJob) in Worker defines what happens when a Job object is received in the WorkerQueue. This is the method that will be executed on the Worker once it receives a new Job. Most likely will consist of return newJob.doWork();
   5. handleResult(object) in Worker defines what happens when a Job is executed on the Worker, and the result is available. This is the method that will be executed on the Worker once it a job has completed execution. Most likely will consist of this.addToResultQueue(result);

3. Once concrete implementations are ready, we are ready to run our Distributed platform. There are two ways to run:

   • Using RMI - To use RMI, we need to create an RMI server. This has been included as the ServerImplementation (which is an implementation of MasterServer). You need to simply create a ServerImplementation with a Master object and a String to bind the Server. Running runServer on this object will start an RMI service. (Note: Start RMI Registry before running ServerImplementation).

     Once the server is up, using the Naming lookup, we can get a remote reference to our MasterServer, create a Job object and run the Job using remoteHandleJob(). A sample of this form of this use case is given in the Tester folder, with the names RMITest and ServerRunner.

   • Using an input queue - Using the JMSHelper, we can get access to the MasterQueue, where we can simply push Job objects to the queue, then run waitFor(job) to get the result. This is the more hands-on approach of the two, and I'd recommend using the RMI to create a truly Distributed system.