Vaughn Vernon - Reactive Messaging Patterns with the Actor Model: Applications and Integration in Scala and Akka

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Applications and Integration in
Scala and Akka

Vaughn Vernon

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Library of Congress Cataloging-in-Publication Data
Vernon, Vaughn.
Reactive messaging patterns with the Actor model : applications and integration in Scala and
Akka / Vaughn Vernon.
pages cm
Includes bibliographical references and index.
ISBN 978-0-13-384683-6 (hardcover : alk. paper)
1. Scala (Computer program language) 2. Application softwareDevelopment. 3. Computer
multitaskingMathematics. 4. Java virtual machine. 5. Business enterprisesData processing.
I. Title.
QA76.73.S28V47 2016
005.2762dc23
2015016389

Copyright 2016 Pearson Education, Inc.

All rights reserved. Printed in the United States of America. This publication is protected by copyright, and permission must be obtained from the publisher prior to any prohibited reproduction, storage in a retrieval system, or transmission in any form or by any means, electronic, mechanical, photocopying, recording, or likewise. To obtain permission to use material from this work, please submit a written request to Pearson Education, Inc., Permissions Department, 200 Old Tappan Road, Old Tappan, New Jersey 07657, or you may fax your request to (201) 236-3290.

ISBN-13: 978-0-13-384683-6
ISBN-10: 0-13-384683-0

Text printed in the United States on recycled paper at Courier in Westford, Massachusetts.
First printing, July 2015

To my dearest Nicole and Tristan.
Your continued love and support are uplifting.

When Carl Hewitt invented the Actor model in the early 1970s he was way ahead of his time. Through the idea of actors he defined a computational model embracing nondeterminism (assuming all communication being asynchronous), which enabled concurrency and, together with the concept of stable addresses to stateful isolated processes, allowed actors to be decoupled in both time and space, supporting distribution and mobility.

Today the world has caught up with Hewitts visionary thinking; multicore processors, cloud computing, mobile devices, and the Internet of Things are the norm. This has fundamentally changed our industry, and the need for a solid foundation to model concurrent and distributed processes is greater than ever. I believe that the Actor model can provide the firm ground we so desperately need in order to build complex distributed systems that are up for the job of addressing todays challenge of adhering to the reactive principles of being responsive, resilient, and elastic. This is the reason I created Akka: to put the power of the Actor model into the hands of the regular developer.

Im really excited about Vaughns book. It provides a much-needed bridge between actors and traditional enterprise messaging and puts actors into the context of building reactive systems. I like its approach of relying only on the fundamentals in Akkathe Actor model and not its high-level librariesas the foundation for explaining and implementing high-level messaging and communication patterns. It is fun to see how the Actor model can, even though it is a low-level computation model, be used to implement powerful and rich messaging patterns in a simple and straightforward manner. Once you understand the basic ideas, you can bring in more high-level tools and techniques.

This book also does a great job of formalizing and naming many of the patterns that users in the Akka community have had to discover and reinvent themselves over the years. I remember enjoying reading and learning from the classic Enterprise Integration Patterns [putting it in a fresh context. But I believe that the most important contribution of this book is that it does not stop there but takes the time to define and introduce a unique pattern language for actor messaging, giving us a vocabulary for how to think about, discuss, and communicate the patterns and ideas.

This is an important bookregardless if you are a newbie or a seasoned hakkerand I hope that you will enjoy it as much as I did.

Jonas Bonr
Founder of the Akka Project

Today, many software projects fail. There are various surveys and reports that show this, some of which report anywhere from 30 to 50 percent failure rates. This number doesnt count those projects that delivered but with distress or that fell short of at least some of the prerequisite success criteria. These failures, of course, include projects for the enterprise. See the Chaos Report [].

At the same time, some notable successes can be found among companies that use Scala and Akka to push the limits of performance and scalability []. So, there is not only success but success in the face of extreme nonfunctional requirements. Certainly it was not Scala and Akka alone that made these endeavors successful, but at the same time it would be difficult to deny that Scala and Akka played a significant role in those successes. I am also confident that those who make use of these tools would stand by their platform decisions as ones that were key to their successes.