SWE 621: Software Modeling and Architectural Design. Lecture Notes on Software Design. Lecture 8 Architectural Design of Distributed Applications

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1 SWE 621: Software Modeling and Architectural Design Lecture Notes on Software Design Lecture 8 Architectural Design of Distributed Applications Hassan Gomaa Dept of Computer Science George Mason University it Fairfax, VA Copyright 2011 H. Gomaa Copyright 2011 Hassan Gomaa All rights reserved. No part of this document may be reproduced in any form or by any means, without the prior written permission of the author. This electronic course material may not be distributed by or posted on any other World Wide Web site without the prior written permission of the author. Overview Collaborative Object Modeling and architectural design method (COMET) Object Oriented Analysis and Design Method Uses UML (Unified Modeling Language) notation Standard approach for describing a software design COMET = UML + Method Provides steps and guidelines for Software Modeling and Design From Use Case Models to Software Architecture H. Gomaa, Software Modeling and Design: UML, Use Cases, Patterns, and Software Architectures, Cambridge University Press, February 2011 Copyright 2011 H. Gomaa 2

2 SWE 621: Software Modeling and Architectural Design Lecture 8: Architectural Design of Distributed Applications Hassan Gomaa Reference: H. Gomaa, Chapters 12, 13, 15 - Software Modeling and Design, Cambridge University Press, February 2011 Copyright 2011 Hassan Gomaa All rights reserved. No part of this document may be reproduced in any form or by any means, without the prior written permission of the author. Copyright 2011 H. Gomaa 3 Steps in Using COMET/UML 1 Develop Software Requirements Model 2 Develop Software Analysis Model 3 Develop Software Design Model Design Overall Software Architecture (Chapter 12, 13) Design Distributed Applications (Chapter 12,13,15) Structure Subsystems into Concurrent Tasks (Chapter 18) Design Information Hiding Classes (Chapter 14) Develop Detailed Software Design Figure 6.1 COMET object-oriented software life cycle model User 1 Requirements 2 Modeling Analysis Modeling 4 3 Throwaway Prototyping 5 Design Modeling 6 Incremental Software Construction 7 Incremental Software Integration 8 Customer Incremental Prototyping 9 15 System Testing Copyright 2006 H. Gomaa Copyright 2011 H. Gomaa 4

3 Architectural Design of Distributed Applications Distributed processing environment Multiple computers communicating over network Typical applications Distributed real-time data collection Distributed real-time control Client / server applications COMET/UML for Distributed Applications Addresses structuring application into distributed subsystems Copyright 2011 H. Gomaa 5 Node 1 Node 2 «local area network» Node 3 Node 4 Distributed processing environment Copyright 2011 H. Gomaa 6

4 Figure 15.1 Basic Client / Server configuration Service «local area network» Client1 Client2 Client3 Copyright 2011 H. Gomaa 7 Figure 15.4 Distributed processing configuration Service1 Service2 «local area network» Client1 Client2 Client3 Copyright 2011 H. Gomaa 8

5 Active and Passive Objects Objects may be active or passive Active object Concurrent task or component Has thread of control Passive object a.k.a. Information Hiding Object Has no thread of control Operations of passive object are executed by task Copyright 2011 H. Gomaa 9 Copyright 2011 H. Gomaa 10

6 Characteristics of Distributed Applications Structure of component-based distributed application Consists of one or more component-based subsystems Each subsystem designed as a distributed component Execute on multiple nodes in distributed configuration Structure of component-based subsystem Consists of one or more objects Objects all execute on same node Communication between component-based subsystems Message communication Copyright 2011 H. Gomaa 11 Steps in Designing Distributed Applications System Decomposition Decompose system into distributed subsystems Each subsystem designed as configurable component Component Active self-contained object with a well-defined interface, capable of being used in different applications from that for which it was originally defined Define message communication interfaces Subsystem Decomposition Structure subsystem into active objects (tasks) and passive objects System Configuration Define component subsystem instances of target system Map to hardware configuration Copyright 2011 H. Gomaa 12

7 Figure Design of Subsystem interfaces high level communication diagram for Banking System Copyright 2011 H. Gomaa 13 Define Subsystem Interfaces Message Communication between distributed subsystems Loosely coupled (asynchronous) message communication Multiple Client / Server message communication Tightly coupled (synchronous) message communication Remote Procedure Call Group Message Communication Broadcast message communication Multicast message communication Object Broker Architecture Negotiation among Software Agents Transaction Processing Copyright 2011 H. Gomaa 14

8 Asynchronous Message Communication (Loosely Coupled) Producer sends message and continues Consumer receives message Suspended if no message is present Activated when message arrives Message queue may build up at Consumer Figure 12.8 Asynchronous message communication Copyright 2011 H. Gomaa 15 Synchronous Message Communication with Reply (Tightly Coupled) Service Responds to message requests from several clients Client Sends message to Service and Waits for response Remote Procedure Call Client makes RPC to service on different node Communication details hidden from client & service Remote method invocation (RMI) Client object sends message to service object Figure 15.7 Synchronous message communication with reply Copyright 2011 H. Gomaa 16

9 Group Message Communication One-to-many message communication Same message sent to several recipients Broadcast message communication Message sent to all recipients Multicast message communication Same message sent to all members of group Subscription/Notification communication Client subscribes to group Receives messages sent to all members of group Sender sends message to group Does not need to know recipients Copyright 2011 H. Gomaa 17 Figure Example of subscription/notification (message multicast) communication Copyright 2011 H. Gomaa 18

10 Distributed Objects and Object broker Clients and Servers designed as distributed objects Object Broker Mediates interactions between clients and servers Frees client from having to maintain information Where particular service provided How to obtain service Servers register Services & Location with Broker Clients request information from Broker about Servers Broker provides different services Copyright 2011 H. Gomaa 19 Object Broker Architecture White pages Client knows name of service but not location Forwarding design Broker forwards client request to Server Broker forwards Server response to Client Handle-driven design Broker returns handle (remote reference) to Client Client uses handle to communicate with Server Copyright 2011 H. Gomaa 20

11 Figure 16.1 Service registration with Broker Services registers service information with Broker Service name Service interface Service description Location Service re-registers after moving to different location abroker R1: register Service R2: registrationack aservice Copyright 2011 H. Gomaa Figure 16.2: Broker Forwarding (White pages) pattern Broker Forwarding Pattern - Broker forwards client request to Service - Broker forwards Service response to Client Copyright 2011 H. Gomaa 22

12 Figure 16.3: Broker Handle (White pages) pattern Broker Handle Pattern - Broker returns handle (remote reference) to Client - Client uses handle to communicate with Service abroker B1: servicerequest B2: servicehandle B3: servicerequestwithhandle aservicerequester aservice B4: servicereply Copyright 2011 H. Gomaa 23 Steps in Using COMET/UML 1 Develop Software Requirements Model 2 Develop Software Analysis Model 3 Develop Software Design Model Design Overall Software Architecture (Chapter 12, 13) Design Distributed Applications (Chapter 12,13,15) Structure Subsystems into Concurrent Tasks (Chapter 18) Design Information Hiding Classes (Chapter 14) Develop Detailed Software Design Figure 6.1 COMET object-oriented software life cycle model User 1 Requirements 2 Modeling Analysis Modeling Design Throwaway Prototyping Modeling 6 Incremental Software Construction 7 Incremental Software Integration 8 Customer Incremental Prototyping 9 System Testing Copyright 2006 H. Gomaa Copyright 2011 H. Gomaa 24