distributed computing

Distributed Computing

DISTRIBUTED COMPUTING

Muhammad Adil Raja

Roaming Researchers, Inc.

cbna

April 24, 2015


OUTLINE I

1 INTRODUCTION

2 REFERENCES


Introduction

INTRODUCTION

In this chapter we will explore some of the implications ofprogramming in a distributed environment.Network programming.Mobile programming.Component based programming.


Introduction

AN OBJECT ORIENTED COMMUNITY

Recall that we have been asserting that an object-orientedprogram is properly thought of as a member of acommunity.If we relax the rules for membership in this community, wemove the paradigm in different directions.

FIGURE : A distributed system.


Introduction

RELAXING THE RULES

What are some of the ways we can relax the rules?Allowing objects to be written in different languages (corba, dcom).Allowing objects on the same machine to form connectionsdynamically (java beans).Allowing objects to reside on different computers (distributed computing).Allowing objects on different computers to formconnections dynamically (mobile computing).All of these are conceptually easy, but the devil is in thedetails.


Client-Server Computing

CLIENT-SERVER COMPUTING

The simplest type of interaction is allowing objects toreside on different computers, but with known interfaces.This is termed client/server computing.The book describes a simple client/server system.



MAKING IT EASIER TO WRITE CLIENT-SERVERSYSTEMS

Java simplifies the production of client/server systems byproviding ready-made library routines for:Address IP addresses or domain names.Ports an address in a computer for creating connections.Sockets a connection between one computer and anaddress/port on another computer.Streams for reading from and writing to a socket.Doesnt mean it cant be done in other languages, but Javamakes it a lot easier since they have spent a lot of timegiving you simple interfaces for these activities.



NEXT LEVEL OF COMPLEXITY

The next level of complexity is a general server who isready to accept connections from many clients, perhapsmany at one time.The book describes a system for this.



OBJECT SPECIALIZATION

Another useful feature (which should perhaps have beendescribed in the metaprogramming chapter) is the ability totransfer objects across a network connection andregenerate them on the far side.Called object serialization, sometimes marshalling.Again, Java has a nice facility for this. Other langaugesmay as well, but Im less familiar with them.The book gives an example of object serialization.



ASKING AN OBJECT ABOUT ITS STATE

Moving back to a single machine, there are systems thatallow a program to dynamically inquire the capabilities ofanother class, and then add it into a running program.A good example is Java Beans, which is not described inthe book.Again, this is built on the reflection facilities described inthe previous chapter.The programmer collects a bunch of components, thenassembles them into a new application.Often components have a visual interface, and can beassembled using a visual tool, without needing to write(much) programming.



ACROSS A NETWORK

The next level of complexity is to do the same sort of thing,but allow the components to exist across the network.This is part of what MS is trying to do with its dot-netprogram.Allow the creation of components which can then beassembled even when they exist on widely separatedcomputers.Many parts of this problem:Registration how do you find out what components existout there?Interface Query how do you find out what interfacesthese components useConnection how do you make a dynamic connection witha remote objectInteraction how do you communicate with a remoteobjectEach of these steps is at the moment unstandarized, but alot of effort is going into each.Expect a lot of work on this in the future.



THE FUTURE

I expect that in three years time this chapter will be a lotricher and a lot thicker.There is an awful lot of work going on in this area right now.Some of these ideas will be successful and continue, somewill die out and be replaced.You should expect to be hearing more about distributing /network / web based computing as time goes on.


References

REFERENCES

Images and content for developing these slides have beentaken from the follwoing book with the permission of theauthor.An Introduction to Object Oriented Programming, TimothyA. Budd.This presentation is developed with Beamer:

JuanLesPins, monarca.

IntroductionReferences

distributed computing

Software