Neal Ford - Building Evolutionary Architectures, 2nd Edition

by Neal Ford , Rebecca Parsons , Patrick Kua , and Pramod Sadalage

Copyright 2023 Neal Ford, Rebecca Parsons, Patrick Kua, and Pramod Sadalage. All rights reserved.

Printed in the United States of America.

Published by OReilly Media, Inc. , 1005 Gravenstein Highway North, Sebastopol, CA 95472.

OReilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://oreilly.com). For more information, contact our corporate/institutional sales department: 800-998-9938 or corporate@oreilly.com.

• Acquisitions Editor: Melissa Duffield
• Development Editor: Virginia Wilson
• Production Editor: Christopher Faucher
• Copyeditor: Audrey Doyle
• Proofreader: Piper Editorial Consulting, LLC
• Indexer: WordCo Indexing Services, Inc.
• Interior Designer: David Futato
• Cover Designer: Karen Montgomery
• Illustrator: OReilly Media, Inc.

• October 2017: First Edition
• December 2022: Second Edition

See http://oreilly.com/catalog/errata.csp?isbn=9781492097549 for release details.

The OReilly logo is a registered trademark of OReilly Media, Inc. Building Evolutionary Architectures, the cover image, and related trade dress are trademarks of OReilly Media, Inc.

The views expressed in this work are those of the authors and do not represent the publishers views. While the publisher and the authors have used good faith efforts to ensure that the information and instructions contained in this work are accurate, the publisher and the authors disclaim all responsibility for errors or omissions, including without limitation responsibility for damages resulting from the use of or reliance on this work. Use of the information and instructions contained in this work is at your own risk. If any code samples or other technology this work contains or describes is subject to open source licenses or the intellectual property rights of others, it is your responsibility to ensure that your use thereof complies with such licenses and/or rights.

978-1-492-09754-9

[LSI]

For a long time, the software industry followed the notion that architecture was something that ought to be developed and completed before writing the first line of code. Inspired by the construction industry, it was felt that the sign of a successful software architecture was something that didnt need to change during development, often a reaction to the high costs of scrap and rework that would occur due to a re-architecture event.

This vision of architecture was rudely challenged by the rise of agile software methods. The preplanned architecture approach was founded on the notion that requirements should also be fixed before coding began, leading to a phased (or waterfall) approach where requirements were followed by architecture which itself was followed by construction (programming). The agile world, however, challenged the very notion of fixed requirements, observing that regular changes in requirements were a business necessity in the modern world and providing project planning techniques to embrace controlled change.

In this new agile world, many people questioned the role of architecture. And certainly the preplanned architecture vision couldnt fit in with modern dynamism. But there is another approach to architecture, one that embraces change in the agile manner. In this perspective, architecture is a constant effort, one that works closely with programming so that architecture can react both to changing requirements and to feedback from programming. Weve come to call this evolutionary architecture, to highlight that while the changes are unpredictable, the architecture can still move in a good direction.

At Thoughtworks, weve been immersed in this architectural worldview. Rebecca led many of our most important projects in the early years of this millennium and developed our technical leadership as our CTO. Neal has been a careful observer of our work, synthesizing and conveying the lessons weve learned. Pat has combined his project work with developing our technical leads. Weve always felt that architecture is vitally important and cant be left to idle chance. Weve made mistakes, but weve learned from them, growing a better understanding of how to build a codebase that can respond gracefully to the many changes in its purpose.

The heart of doing evolutionary architecture is to make small changes and put in feedback loops that allow everyone to learn from how the system is developing. The rise of Continuous Delivery has been a crucial enabling factor in making evolutionary architecture practical. The authorial trio use the notion of fitness functions to monitor the state of the architecture. They explore different styles of evolvability for architecture and emphasize the issues around long-lived dataoften a topic that gets neglected. Conways Law towers over much of the discussion, as it should.

While Im sure we have much to learn about doing software architecture in an evolutionary style, this book marks an essential road map for the current state of understanding. As more people are realizing the central role of software systems in our 21st-century human world, knowing how best to respond to change while keeping on your feet will be an essential skill for any software leader.

Martin Fowler

martinfowler.com

September 2017