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

Upgrading while staying online

We've all encountered this scenario. PostgreSQL recently released version 9.6.1 and we need to upgrade to protect ourselves from potential data corruption. Or perhaps it isn't PostgreSQL that requires an upgrade, but the system kernel or another critical element of the operating system.

Regardless of the reason, we must accommodate the procedure somehow. Upgrading software while remaining online is the ultimate aspiration of maintaining a high availability stack. Let's see how we can reach that goal by leveraging Patroni's functionality.

Getting ready

This recipe depends on the presence of the entire stack. Please complete all recipes up to Installing and configuring HAProxy before continuing.

How to do it...

For this recipe, we should still have three PostgreSQL servers. As usual, we'll assume they are named pg1, pg2, and pg3. If pg1 is the initial leader, follow these steps to perform an in-place system upgrade:

  1. Start a status monitor on pg3 with the following...