Douglas C. Schmidt - Pattern-Oriented Software Architecture, Patterns for Concurrent and Networked Objects

Patterns for Concurrent and Networked Objects

The Wrapper Facade design pattern (47) encapsulates the functions and data provided by existing non-object-oriented APIs within more concise, robust, portable, maintainable, and cohesive object-oriented class interfaces.

The Component Configurator design pattern (75) allows an application to link and unlink its component implementations at run-time without having to modify, recompile, or statically relink the application. Component Configurator further supports the reconfiguration of components into different application processes without having to shut down and re-start running processes.

The Interceptor architectural pattern (109) allows services to be added transparently to a framework and triggered automatically when certain events occur.

The Extension Interface design pattern (141) allows multiple interfaces to be exported by a component, to prevent bloating of interfaces and breaking of client code when developers extend or modify the functionality of the component.

The Reactor architectural pattern (179) allows event-driven applications to demultiplex and dispatch service requests that are delivered to an application from one or more clients.

The Proactor architectural pattern (215) allows event-driven applications to efficiently demultiplex and dispatch service requests triggered by the completion of asynchronous operations, to achieve the performance benefits of concurrency without incurring certain of its liabilities.

The Asynchronous Completion Token design pattern (261) allows an application to demultiplex and process efficiently the responses of asynchronous operations it invokes on services.

The Acceptor-Connector design pattern (285) decouples the connection and initialization of cooperating peer services in a networked system from the processing performed by the peer services after they are connected and initialized.

The Scoped Locking C++ idiom (325) ensures that a lock is acquired when control enters a scope and released automatically when control leaves the scope, regardless of the return path from the scope.

The Strategized Locking design pattern (333) parameterizes synchronization mechanisms that protect a components critical sections from concurrent access.

The Thread-Safe Interface design pattern (345) minimizes locking overhead and ensures that intra-component method calls do not incur self-deadlock by trying to reacquire a lock that is held by the component already.

The Double-Checked Locking Optimization design pattern (353) reduces contention and synchronization overhead whenever critical sections of code must acquire locks in a thread-safe manner just once during program execution.

The Active Object design pattern (369) decouples method execution from method invocation to enhance concurrency and simplify synchronized access to objects that reside in their own threads of control.

The Monitor Object design pattern (399) synchronizes concurrent method execution to ensure that only one method at a time runs within an object. It also allows an objects methods to cooperatively schedule their execution sequences.

The Half-Sync/Half-Async architectural pattern (423) decouples asynchronous and synchronous service processing in concurrent systems, to simplify programming without unduly reducing performance. The pattern introduces two intercommunicating layers, one for asynchronous and one for synchronous service processing.

The Leader/Followers architectural pattern (447)provides an efficient concurrency model where multiple threads take turns sharing a set of event sources in order to detect, demultiplex, dispatch, and process service requests that occur on the event sources.

The Thread-Specific Storage design pattern (475) allows multiple threads to use one logically global access point to retrieve an object that is local to a thread, without incurring locking overhead on each object access.

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British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library

ISBN 978-0-471-60695-6 (hbk)

For Sonja, Mom, and Dad

Douglas C. Schmidt

For Gisela

Michael Stal

For Regine, Anja, Sandro, and Nicolas

Hans Rohnert

For Beb and Martina

Frank Buschmann

Beb, July 3, 1999

Foreword

Middleware is the set of services, protocols, and support utilities providing the plumbing that makes modern distributed systems and applications possiblethe infrastructure that underlies web services, distributed objects, collaborative applications, e-commerce systems, and other important platforms. Not long ago, the term middleware was rarely heard, and middleware developers were rarer still. But over the past decade, the term, the research and practice, and its impact have become ubiquitous. Yet, until now, there has not been a book describing how to construct networked and concurrent object-oriented (OO) middleware, so its design has remained something of a black art. This book demystifies middleware construction, replacing the need to have an expert looking over your shoulder with well-reasoned, empirically-guided accounts of common design problems, forces, successful solutions, and consequences.