Book Image

High Availability MySQL Cookbook

By : Alexander Davies
Book Image

High Availability MySQL Cookbook

By: Alexander Davies

Overview of this book

High Availability is something that all web sites hope to achieve, especially those that are linked to big companies.MySQL, an open source relational database management system (RDBMS), can be made highly available to protect from corruption, hardware failure, software crashes, and user error. Running a MySQL setup is quite simple. Things start getting complex when you start thinking about the best way to provide redundancy. There are a large number of techniques available to add 'redundancy' and 'high availability' to MySQL, but most are both poorly understood and documented.This book will provide you with recipes showing how to design, implement, and manage a MySQL Cluster and achieve high availability using MySQL replication, block level replication, shared storage, and the open source Global File System (GFS).This book covers all the major techniques available for increasing availability of your MySQL databases. It demonstrates how to design, implement, troubleshoot and manage a highly available MySQL setup using any one of several techniques, which are shown in different recipes. It is based on MySQL Cluster 7.0, MySQL (for non clustered recipes) 5.0.77, and CentOS / RedHat Enterprise Linux 5.3.The book starts by introducing MySQL Cluster as a technology and explaining how to set up a simple cluster. It will help you to master the options available for backing up and restoring a file in the MySQL Cluster. By following the practical examples in this book, you will learn how to manage the MySQL Cluster. Further, we will discuss some troubleshooting aspects of the MySQL Cluster.We also have a look at achieving high availability for MySQL databases with the techniques of MySQL Replication, block level replication, shared storage (a SAN or NAS), and DRBD.Finally, you will learn the principles of Performance tuning and tune MySQL database for optimal performance.
Table of Contents (17 chapters)
High Availability MySQL Cookbook
Credits
About the Author
About the Reviewers
Preface
Base Installation
Index

Restricting write access to a MySQL Cluster with single-user mode


Most MySQL Clusters will have more than one SQL node (mysqld process) as well as the option for other API nodes such as ndb_restore to connect to the cluster. Occasionally, it is essential for only one API node to access the cluster. MySQL Cluster has a single-user mode which, allows you to temporarily specify only a single API node that may execute the queries against the cluster.

In this recipe, we will use an example cluster with two SQL nodes, nodeIDs 13 and 14, execute a query against both the nodes, enter single-user mode, repeat the experiment, and finish by verifying that once the single user mode is exited, the query works as it did at the beginning of the exercise.

Note

Within a single SQL node, the standard MySQL LOCK TABLES queries will work as expected, if no other nodes are changing the data in NDBCLUSTER tables. The only way to be sure of this is to use a single-user mode.

How to do it…

A single-user mode is controlled...