Bell Charles - MySQL High Availability

A lot of research has been done on replication, but most of the resulting concepts are never put into production. In contrast, MySQL replication is widely deployed but has never been adequately explained. This book changes that. Things are explained here that were previously limited to people willing to read a lot of source code and spend a lot of time debugging it in production, including a few late-night sessions.

Replication enables you to provide highly available data services while enduring the inevitable failures. There are an amazing number of ways for things to fail, including the loss of a disk, server, or data center. Even when hardware is perfect or fully redundant, people are not. Database tables will be dropped by mistake. Applications will write incorrect data. Occasional failure is assured. But with reasonable preparation, recovery from failure can also be assured. The keys to survival are redundancy and backups. Replication in MySQL supports both.

But MySQL replication is not limited to supporting failure recovery. It is frequently used to support read scale-out. MySQL can efficiently replicate to a large number of servers. For applications that are read-mostly, this is a cost-effective strategy for supporting a large number of queries on commodity hardware.

And there are other interesting uses for MySQL replication. Online DDL is a very complex feature to implement in an relational database management system. MySQL does not support online DDL, but through the use of replication you can implement something that is frequently good enough. You can get a lot done with replication if you are willing to be creative.

Replication is one of the features that made MySQL wildly popular. It is also the feature that allows you to convert a popular MySQL prototype into a successful business-critical deployment. Like most of MySQL, replication favors simplicity and ease of use. As a consequence, it is occasionally less than perfect when running in production. This book explains what you need to know to successfully use MySQL replication. It will help you to understand how replication has been implemented, what can go wrong, how to prevent problems, and how to fix them when they crop up despite your best attempts at prevention.

MySQL replication is also a work in progress. Change, like failure, is also assured. MySQL is responding to that change and replication continues to get more efficient, more robust, and more interesting. For instance, row-based replication is new in MySQL 5.1.

While MySQL deployments come in all shapes and sizes, I care most about data services for Internet applications and am excited about the potential to replicate from MySQL to distributed storage systems like HBase and Hadoop. This will make MySQL better at sharing the data center.

I have been on teams that support important MySQL deployments at Facebook and Google. I have had the opportunity, problems, and time to learn much of what is covered in this book. The authors of this book are also experts on MySQL replication, and by reading this book you can share their expertise.