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

Using an outage to test availability

Every high availability cluster must possess the capability to detect and route around server failures. Hardware faults, virtual instance crashes, mistyped commands, and any number of potential disasters lurk around every corner. The best way to determine the true resilience of our stack is to test it by breaking something.

Let's see what happens by attacking Patroni directly.

Getting ready

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

How to do it...

For this recipe, we should already have three PostgreSQL servers. As usual, we'll assume they are named pg1, pg2, and pg3. If pg2 is the current primary, follow these steps to simulate a server failure:

  1. Execute the following command as the postgres user on pg2:
pkill -f patroni
  1. Follow the Patroni log on pg1 or pg3 with this command:
tail -f /var/log/postgresql/patroni.log

How it works...

This recipe relies on a dirty...