Book Image

PostgreSQL High Availability Cookbook - Second Edition

By : Shaun Thomas
Book Image

PostgreSQL High Availability Cookbook - Second Edition

By: Shaun Thomas

Overview of this book

Databases are nothing without the data they store. In the event of a failure - catastrophic or otherwise - immediate recovery is essential. By carefully combining multiple servers, it’s even possible to hide the fact a failure occurred at all. From hardware selection to software stacks and horizontal scalability, this book will help you build a versatile PostgreSQL cluster that will survive crashes, resist data corruption, and grow smoothly with customer demand. It all begins with hardware selection for the skeleton of an efficient PostgreSQL database cluster. Then it’s on to preventing downtime as well as troubleshooting some real life problems that administrators commonly face. Next, we add database monitoring to the stack, using collectd, Nagios, and Graphite. And no stack is complete without replication using multiple internal and external tools, including the newly released pglogical extension. Pacemaker or Raft consensus tools are the final piece to grant the cluster the ability to heal itself. We even round off by tackling the complex problem of data scalability. This book exploits many new features introduced in PostgreSQL 9.6 to make the database more efficient and adaptive, and most importantly, keep it running.
Table of Contents (18 chapters)
Title Page
About the Author
About the Reviewer
Customer Feedback

Swapping active nodes with pgpool

With pgpool installed, we have an abstraction layer above PostgreSQL, which hides the active node from the client. This allows us to change the primary node so that we can perform maintenance, and yet we never have to actually stop the database.

This kind of design will work best when pgpool is not installed on one of the PostgreSQL servers, but it has its own dedicated hardware or virtual machine. This allows us full control over each PostgreSQL server, including the ability to reboot for kernel upgrades, without potentially disrupting pgpool.

Let's discuss the elements involved in switching the primary server with a replica so that we can have high availability in addition to regular maintenance.

Getting ready

Make sure pgpool is installed and configured according to the Installing pgpool and Configuring pgpool for master/slave mode recipes. We will need two nodes so that we can promote one and demote the other.

Next, we will ready the operating system so that...