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

Performing a managed failover

Managing a Patroni cluster is relatively easy as long as it's operating normally. The primary reason for this is the provided patronictl command-line tool. Beyond simply displaying cluster status, it also manages several other helpful operations.

In particular, we can use it to force the primary node to step down and allow one of the replicas to take its place. In a high availability context, this is a great way to perform system upgrades. We merely need switch to another primary, upgrade the old system, and repeat. We're done when every node is the latest PostgreSQL version. During this process, the database is never offline. This procedure also works for regular system maintenance.

Let's see how to change the primary node using Patroni.

Getting ready

This recipe depends on the presence of the entire stack. Please complete all previous recipes in this chapter before continuing.

How to do it...

For this recipe, we should already have three PostgreSQL servers. As usual...