www.it-ebooks.info www.it-ebooks.info Cassandra: The Definitive Guide www.it-ebooks.info www.it-ebooks.info Cassandra: The Definitive Guide Eben Hewitt Beijing • Cambridge • Farnham • Köln • Sebastopol • Tokyo www.it-ebooks.info Cassandra: The Definitive Guide by Eben Hewitt Copyright © 2011 Eben Hewitt. All rights reserved. Printed in the United States of America. Published by O’Reilly Media, Inc., 1005 Gravenstein Highway North, Sebastopol, CA 95472. O’Reilly books may be purchased for educational, business, or sales promotional use. Online editions are also available for most titles (http://my.safaribooksonline.com). For more information, contact our corporate/institutional sales department: (800) 998-9938 or corporate@oreilly.com. Editor: Mike Loukides Production Editor: Holly Bauer Copyeditor: Genevieve d’Entremont Proofreader: Emily Quill Indexer: Ellen Troutman Zaig Cover Designer: Karen Montgomery Interior Designer: David Futato Illustrator: Robert Romano Printing History: November 2010: First Edition. Nutshell Handbook, the Nutshell Handbook logo, and the O’Reilly logo are registered trademarks of O’Reilly Media, Inc. Cassandra: The Definitive Guide, the image of a Paradise flycatcher, and related trade dress are trademarks of O’Reilly Media, Inc. Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and O’Reilly Media, Inc. was aware of a trademark claim, the designations have been printed in caps or initial caps. While every precaution has been taken in the preparation of this book, the publisher and author assume no responsibility for errors or omissions, or for damages resulting from the use of the information con- tained herein. TM This book uses RepKover™, a durable and flexible lay-flat binding. ISBN: 978-1-449-39041-9 [M] 1289577822 www.it-ebooks.info This book is dedicated to my sweetheart, Alison Brown. I can hear the sound of violins, long before it begins. www.it-ebooks.info www.it-ebooks.info Table of Contents Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii 1. Introducing Cassandra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 What’s Wrong with Relational Databases? 1 A Quick Review of Relational Databases 6 RDBMS: The Awesome and the Not-So-Much 6 Web Scale 12 The Cassandra Elevator Pitch 14 Cassandra in 50 Words or Less 14 Distributed and Decentralized 14 Elastic Scalability 16 High Availability and Fault Tolerance 16 Tuneable Consistency 17 Brewer’s CAP Theorem 19 Row-Oriented 23 Schema-Free 24 High Performance 24 Where Did Cassandra Come From? 24 Use Cases for Cassandra 25 Large Deployments 25 Lots of Writes, Statistics, and Analysis 26 Geographical Distribution 26 Evolving Applications 26 Who Is Using Cassandra? 26 Summary 28 2. Installing Cassandra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Installing the Binary 29 Extracting the Download 29 vii www.it-ebooks.info What’s In There? 29 Building from Source 30 Additional Build Targets 32 Building with Maven 32 Running Cassandra 33 On Windows 33 On Linux 33 Starting the Server 34 Running the Command-Line Client Interface 35 Basic CLI Commands 36 Help 36 Connecting to a Server 36 Describing the Environment 37 Creating a Keyspace and Column Family 38 Writing and Reading Data 39 Summary 40 3. The Cassandra Data Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 The Relational Data Model 41 A Simple Introduction 42 Clusters 45 Keyspaces 46 Column Families 47 Column Family Options 49 Columns 49 Wide Rows, Skinny Rows 51 Column Sorting 52 Super Columns 53 Composite Keys 55 Design Differences Between RDBMS and Cassandra 56 No Query Language 56 No Referential Integrity 56 Secondary Indexes 56 Sorting Is a Design Decision 57 Denormalization 57 Design Patterns 58 Materialized View 59 Valueless Column 59 Aggregate Key 59 Some Things to Keep in Mind 60 Summary 60 viii | Table of Contents www.it-ebooks.info [...]... enormous volumes of data; the fact that it does stands as a monument to the ingenious architecture of the Web But some of this infrastructure is starting to bend under the weight In 1966, a company like IBM was in a position to really make people listen to their innovations They had the problems, and they had the brain power to solve them As we enter the second decade of the 21st century, we’re starting... for some length of time; that’s the very point of making updates— that they’re there for others to read However, a more subtle examination might lead us to want to find a way to tune these properties a bit and control them slightly There is, as they say, no free lunch on the Internet, and once we see how we’re paying for our transactions, we may start to wonder whether there’s an alternative Transactions... DB2 database gets its name as the successor to DB1 the product built around the hierarchical data model IMS IMS was released in 1968, and subsequently enjoyed success in Customer Information Control System (CICS) and other applications It is still used today But in the years following the invention of IMS, the new model, the disruptive model, the threatening model, was the relational database In his... www.it-ebooks.info RDBMS, NoSQL The horse, the car, the plane They each build on prior art, they each attempt to solve certain problems, and so they’re each good at certain things—and less good at others They each coexist, even now So let’s examine for a moment why, at this point, we might consider an alternative to the relational database, just as Codd himself four decades ago looked at the Information Management... through the use of transactions, which require locking some portion of the database so it’s not available to other clients This can become untenable under very heavy loads, as the locks mean that competing users start queuing up, waiting for their turn to read or write the data We typically address these problems in one or more of the following ways, sometimes in this order: • Throw hardware at the problem... and updates in the database, which is exacerbated over a cluster • We turn our attention to the database again and decide that, now that the application is built and we understand the primary query paths, we can duplicate some of the data to make it look more like the queries that access it This process, called denormalization, is antithetical to the five normal forms that characterize the relational... www.it-ebooks.info www.it-ebooks.info CHAPTER 1 Introducing Cassandra If at first the idea is not absurd, then there is no hope for it —Albert Einstein Welcome to Cassandra: The Definitive Guide The aim of this book is to help developers and database administrators understand this important new database, explore how it compares to the relational database management systems we’re used to, and help you put... same time, then one of them will have to wait for the other to complete Durable Once a transaction has succeeded, the changes will not be lost This doesn’t imply another transaction won’t later modify the same data; it just means that writers can be confident that the changes are available for the next transaction to work with as necessary On the surface, these properties seem so obviously desirable as... First, the new model was very different from the old model, which it pointedly controverted It was threatening because it can be hard to understand something different and new Ensuing debates can help entrench people stubbornly further in their views—views that might have been 1 www.it-ebooks.info largely inherited from the climate in which they learned their craft and the circumstances in which they... a day, and in other Web 2.0 applications The idea here is that you split the data so that instead of hosting all of it on a single server or replicating all of the data on all of the servers in a cluster, you divide up portions of the data horizontally and host them each separately For example, consider a large customer table in a relational database The least disruptive thing (for the programming . www.it-ebooks.info www.it-ebooks.info Cassandra: The Definitive Guide www.it-ebooks.info www.it-ebooks.info Cassandra: The Definitive Guide Eben Hewitt Beijing • Cambridge • Farnham • Köln • Sebastopol • Tokyo www.it-ebooks.info Cassandra:. 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