Building Microservices

Preface

Microservices are an approach to distributed systems that promote the use of finely grained services with their own lifecycles, which collaborate together. Because microservices are primarily modeled around business domains, they avoid the problems of traditional tiered architectures. Microservices also integrate new technologies and techniques that have emerged over the last decade, which helps them avoid the pitfalls of many service-oriented architecture implementations.

This book is full of concrete examples of microservice use around the world, including in organizations like Netflix, Amazon, Gilt, and the REA group, who have all found that the increased autonomy this architecture gives their teams is a huge advantage.

Who Should Read This Book

The scope of this book is broad, as the implications of fine-grained microservice architectures are also broad. As such, it should appeal to people interested in aspects of design, development, deployment, testing, and maintenance of systems. Those of you who have already embarked on the journey toward finer-grained architectures, whether for a greenfield application or as part of decomposing an existing, more monolithic system, will find plenty of practical advice to help you. It will also help those of you who want to know what all the fuss is about, so that you can determine whether microservices are right for you.

Why I Wrote This Book

I started thinking about the topic of application architectures many years ago, when working to help people deliver their software faster. I realized that while infrastructure automation, testing, and continuous delivery techniques could help, if the fundamental design of the system doesn’t make it easy to make changes, then there are limits to what can be accomplished.

At the same time, many organizations were experimenting with finer-grained architectures to accomplish similar goals, but also to achieve things like improved scaling, increasing autonomy of teams, or to more easily embrace new technologies. My own experiences, as well as those of my colleagues at ThoughtWorks and elsewhere, reinforced the fact that using larger numbers of services with their own independent lifecycles resulted in more headaches that had to be dealt with. In many ways, this book was imagined as a one-stop shop that would help encompass the wide variety of topics that are necessary for understanding microservices—something that would have helped me greatly in the past!

A Word on Microservices Today

Microservices is a fast-moving topic. Although the idea is not new (even if the term itself is), experiences from people all over the world, along with the emergence of new technologies, are having a profound effect on how they are used. Due to the fast pace of change, I have tried to focus this book on ideas more than specific technologies, knowing that implementation details always change faster than the thoughts behind them. Nonetheless, I fully expect that in a few years from now we’ll have learned even more about where microservices fit, and how to use them well.

So while I have done my best to distill out the essence of the topic in this book, if this topic interests you, be prepared for many years of continuous learning to keep on top of the state of the art!

Navigating This Book

This book is primarily organized in a topic-based format. As such, you may want to jump into the specific topics that interest you the most. While I have done my best to reference terms and ideas in the earlier chapters, I’d like to think that even people who consider themselves fairly experienced will find something of interest in all chapters here. I would certainly suggest that you take a look at Chapter 2, which touches on the breadth of the topic as well as providing some framing for how I go about things in case if you want to dive deeper into some of the later topics.

For people new to the subject, I’ve structured the chapters in a way that I hope will make sense to read from beginning to end.

Here is an overview of what we cover:

Chapter 1, Microservices

We’ll begin with an introduction to microservices, including the key benefits as well as some of the downsides.

Chapter 2, The Evolutionary Architect

This chapter discusses the difficulties we face in terms of making trade-offs as architects, and covers specifically just how many things we need to think about with microservices.

Chapter 3, How to Model Services

Here we’ll start to define the boundary of microservices, using techniques from domain-driven design to help focus our thinking.

Chapter 4, Integration

This is where we start getting a bit deeper into specific technology implications, as we discuss what sorts of service collaboration techniques will help us most. We’ll also delve into the topic of user interfaces and integrating with legacy and commercial off-the-shelf (COTS) products.

Chapter 5, Splitting the Monolith

Many people get interested in microservices as an antidote to large, hard-to-change monolithic systems, and this is exactly what we’ll cover in detail in this chapter.

Chapter 6, Deployment

Although this book is primarily theoretical, few topics in the book have been as impacted by recent changes in technology as deployment, which we’ll explore here.

Chapter 7, Testing

This chapter goes deep into the topic of testing, an area of particular concern when handling the deployment of multiple discrete services. Of particular note will be the role that consumer-driven contracts can play in helping us ensure the quality of our software.

Chapter 8, Monitoring

Testing our software before production doesn’t help if problems occur once we go live, and this chapter explores how we can monitor our fine-grained systems and deal with some of the emergent complexity of distributed systems.

Chapter 9, Security

Here we’ll examine the security aspects of microservices and consider how to handle user-to-service and service-to-service authentication and authorization. Security is a very important topic in computing, one that is all too readily ignored. Although I am in no way a security expert, I hope that this chapter will at least help you consider some of the aspects you need to be aware of when building systems, and microservice systems in particular.

Chapter 10, Conway’s Law and System Design

This chapter focuses on the interplay of organizational structure and architecture. Many organizations have realized that trouble will occur if you don’t keep the two in harmony. We’ll attempt to get to the bottom of this dilemma, and consider some different ways to align system design with the structure of your teams.

Chapter 11, Microservices at Scale

This is where we start looking at doing all of this at scale, so that we can handle the increased chance of failure that can happen with large numbers of services, as well as large volumes of traffic.

Chapter 12, Bringing It All Together

The final chapter attempts to distill down the core essence of what makes microservices different. It includes a list of seven microservices principles, as well as a wrap-up of the key points of the book.

Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, and file extensions.

Constant width

Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.

Constant width bold

Shows commands or other text that should be typed literally by the user.

Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.

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Acknowledgments

This book is dedicated to Lindy Stephens, without whom it wouldn’t exist. She encouraged me to start on this journey, supported me throughout the often stressful process of writing, and is the best partner I could have ever asked for. I would also like to dedicate this to my dad, Howard Newman, who has always been there for me. This is for both of you.

I would like to single out Ben Christensen, Venkat Subramaniam, and Martin Fowler for providing detailed feedback throughout the writing process, helping shape what this book became. I’d also like to thank James Lewis, with whom I have consumed many beers discussing the ideas presented in this book. This book would be a shadow of itself without their help and guidance.

In addition, many others provided help and feedback on early versions of the book. Specifically, I would like to thank (in no particular order) Kane Venables, Anand Krishnaswamy, Kent McNeil, Charles Haynes, Chris Ford, Aidy Lewis, Will Thames, Jon Eaves, Rolf Russell, Badrinath Janakiraman, Daniel Bryant, Ian Robinson, Jim Webber, Stewart Gleadow, Evan Bottcher, Eric Sword, Olivia Leonard, and all my other colleagues at ThoughtWorks and across the industry who have helped me get this far.

Finally, I would like to thank all the people at O’Reilly, including Mike Loukides for getting me on board, my editor Brian MacDonald, Rachel Monaghan, Kristen Brown, Betsy Waliszewski, and all the other people who have helped in ways I may never know about.