COIT20257 Assignment 1 Specification and Marking Criteria
Due date: Friday of Week 5 (14th August 2020) 11.55 pm AEST
ASSESSMENT Weighting: 30%
Length: NA 1
Objectives
• Develop distributed applications using networking, inter-process communication, and remote invocation
• Solve problems in the distributed systems domain by applying the principles of distributed systems to authentic problems
Assignment Title: A Simplified Remote Invocation Framework
The application background
Java RMI (Remote Method Invocation, reference Chapter 5 of the textbook and Week-3 lecture) enables the local invocation and remote invocation use the same syntax to implement a generic remote server like the Compute Engine example in Week-3 lecture slides. The application background of such a compute engine is to utilise the compute-power of a high-performance computer or cluster. That is, a client prepares compute-tasks and submits them to the server for execution. Java RMI framework needs two HTTP servers to transfer Java classes between an RMI client and an RMI server at runtime. In addition, Java RMI applications need an RMI Registry to register or look up the remote objects. In this assignment, you are to implement a remote invocation framework that is similar to Java RMI but lightweight (note: for this assignment, you don’t use any Java RMI APIs).
Java TCP streaming, object serialization, multithreading and client/server model are the fundamental Java components to build distributed applications. These models and components have been introduced through Week 1 to Week 5 lectures, tutorials and lab projects of this unit. These models and components are enough to develop such a simplified framework of this assignment. You will need review these models and components and practise relevant lab projects of these weeks for this assignment.
This assignment specification is as follows.
Part 1: Java TCP streaming, Multithreading and Object Serialization Programming
The framework consists of a compute-server, a compute-client and a class repository, which are depicted in the following diagram. The framework is a generic computing architecture because the compute-client and compute-server just need to know the Task interface and CSMessage class as the communication contract to interact with each other via the framework. The specification of the components is as follows.
1. The interaction contract
The interaction contract between a compute-client and the compute-server consists of the Task interface and the CSMessage class.
1. The Task interface defines two standard methods that every compute-task must implements. For example, in this assignment, three compute-tasks CalculatePi.class, CalculatePrime.class and CalculateGCD.class
all implement the task interface.
package Contract; public interface Task { public void executeTask(); public Object getResult();
}
2. The CSMessage class is a special implementation of the Task interface. The CSMessage class is handling exceptions.
public class CSMessage implements Task, Serializable { //The variable that holds the error information private String finalResult;
public CSMessage() {
}
//Return the error message public Object getResult() { return finalResult;
}
//Set the error message public void setMessage(String msg) {
finalResult=msg;
}
public void executeTask() {
}
}
When there is an exception occurred (e.g. a compute-client wants the compute-server to perform a compute-task but forgets uploading the Java class of the compute-task onto the class repository of the compute-server), the compute-server creates a CSMessage object filled with the exception message and sends it back to the compute-client. By calling the getResult() method, the compute-client gets the exception message.
2. The compute-task
A compute-task must implement the Task interface. Executing the executeTask() method will perform the task and set the result. Calling the getResult() method will return the result. A compute-task must implement java.io.Serializable interface as well so that the compute-task can be transferred between the compute-server and a compute-client over the network. The structure of a compute-class is as follows. public class CalculatePi implements Task, Serializable{
……
@Override
public void executeTask() { //The implementation of method
……
}
@Override
public Object getResult() { //The implementation of method
……
}
//may have other methods
……
}
Every compute-task class is defined in the compute-client and it must be uploaded to the class repository of the compute-server. Every compute-task object is created in the compute-client and submitted to the server to execute.
3. The class repository
The compute-server has a class repository that saves the Java classes of available compute-tasks.
Before asking the compute-server to perform a compute-task, a compute-client must upload the Java class of the task onto the class repository. The uploading of compute-tasks is automated by the client and the server, not manually by a user.
The following screenshots show that when the compute-server starts, it is listening on two ports for object or file transfer. the class repository has no real compute-tasks except the communication contract Task interface and CSMessage class.
The real compute-tasks are created in the client side. As shown in the following screenshot, there are three compute-tasks: CalaulatePi, CalculatePrime and CalculateGCD in
the client side.
4. The interaction workflow of the framework
When the compute-client starts as shown in the following screenshots, the server name and ports need to be set. Clicking the Set button will:
1. Establish two TCP connections to the server on the given ports, one for object transfer and the other for file transfer.
2. Update the task drop-down list to include the available tasks.
3. Enable the Upload and Calculate buttons.
Selecting a task (e.g. Calculate Pi) and clicking the Upload button, the Java class of selected task (e.g. CalaulatePi.class) will be uploaded to the class repository of the compute-sever as shown in the following screenshots.
Clicking the Calculate button will collect the arguments for the selected task. For example, for Calculate Pi, the argument is the number of decimal places to calculate Pi for certain accuracy.
Clicking the OK button will involve the following interaction between the client and the server.
1. The client creates a CalaulatePi object and sends to the server.
2. The server receives the CalaulatePi object and cast (deserialize) the task into the Task interface type.
3. The server calls its executeTask() method, which performs the computation and sets the result on the same object.
4. The compute-server sends the same CalaulatePi object back to the compute-client.
5. The client receives the CalaulatePi object back from the server.
6. The compute-client calls the getResult() method of the object to retrieve and display the result.
The state of the class repository, the output of the compute-client and the compute-server are shown in the following screenshots.
In the same way the compute-client can ask the compute-server to perform other tasks as shown in the following screenshots.
5. The error message
However, when there is an exception occurred, the compute-server will create a CSMessage and send to the compute-client. The following screenshots show the situation of calling the compute-server before the compute-task ComputeGCD is uploaded.
The following screenshots show the situation of calling the compute-server after the computetask ComputeGCD is uploaded.
6. The implementation
To complete this assignment, you need to implement such a framework and integrate the Calculate Pi, Calculate Primes and Calculate the Greatest Common Divisor tasks into this framework. The algorithms of these tasks are given on the unit web site. The sample code of transferring binary files over networks has been provided on the unit web site. The computeserver must be multi-threaded and follow the ‘thread-per-connection’ architecture (reference Week-4 contents). The communication between the compute-server and the compute-client must use TCP streaming by using Java TCP API Socket and ServerSocket as described in
Week-2 contents of this unit and also online at, https://docs.oracle.com/javase/8/docs/api/java/net/Socket.html, and https://docs.oracle.com/javase/8/docs/api/java/net/ServerSocket.html). Please note: use of any other protocols will incur no marks to be awarded for this part.
To implement the framework, you need to implement the following Java classes:
1. A Java application to implement the compute-client; graphic user interface (GUI) is required. The GUI should have the necessary components to enable the user to execute all the functions as provided as in this assignment specification;
2. A Java application to implement the compute-server; and
3. A number of Java class to implement the processing threads when necessary.
Note: to demonstrate your competence of concurrency programming, you will need to make an analysis on when concurrency is needed. Marks will be deducted if concurrency is not identified or necessary multithreading is not used.
4. A number of Java classes to implement Calculate Pi, Calculate Primes and Calculate the Greatest Common Divisor tasks.
Note: to simulate compute-client and compute-server interaction, you don’t have to run them on two physical machines. Instead, they can be run on two JVMs (Java Virtual Machines) on a single physical machine. As a result, the name of the server machine can be ‘localhost’.
Part 2: Program use and test instruction
After the implementation of the framework, prepare an end user’ instruction about how to use your software. The instruction should cover all aspects of the framework as detailed in the Part 2 of marking criteria below.
Submission
You need to provide the following files in your submission.
1. Files of Java source code of the compute-client, the compute-server and the processing thread and the compute-tasks. The inline comments on the data structure and program structure in the programs are required. These source code files must be able to be compiled by the standard JDK (Java Development Kit) or NetBeans IDE from Oracle.
2. The compiled Java class files of the source code. These Java classes must be runnable on the standard Java Runtime Environment (JRE) from Oracle
(http://www.oracle.com/technetwork/java/index.html).
Note: an easy way to provide the source code and executables is to submit them in a NetBeans project.
3. A Microsoft Word document to address the issues as specified in Part 2 above.
All the required files must be compressed into a zip file for submission. You must submit your assignment via the unit web site. Any hardcopy or email submission will not be accepted. After the marked assignments are returned, any late submissions will not be accepted.
The Marking Criteria
Marking Criteria Available Marks
Part 1: Java TCP streaming, Multi-threading and Object Serialization Programming 21
1. Whether the project can be compiled by JDK or NetBeans IDE and executed by JRE 2
2. Whether the given Task interface is properly used as the unique communication contract between the client and server 2
3. Whether the 3 compute-tasks have been implemented
as Java serializable objects 3
4. Whether the 3 compute-tasks can be successfully transferred between the client and server 3
5. Whether the 3 compute-tasks can be successfully executed by the server and can return correct results to the client 3
6. Whether the ‘not uploading task’ exception can be handled by using the CSMessage 2
7. Whether the client program functions correctly 2
8. Whether TCP streaming is correctly used for the client and server communication 2
9. Whether the sever structure is sound as a TCP server 2
Part 2: Program use and test instruction 9
1. Whether the program compiling and installation is clearly described 2
2. Whether the code repository in the server is clearly described 1
3. Whether the test instruction covers all 3 computetasks 3
4. Whether the test instruction covers ‘not uploading task’ exception handling. 1
5. Whether the necessary screenshots and source code inline comments have been provided 2
Sub Total for Assignment 1 30
Late Penalty -1.5 (5%) each calendar day(either full or partial)
Plagiarism Related Penalty
Total for Assignment 1