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

Preparing startup services

A common interpretation of a functional server is one that runs on its own recognizance. After being rebooted, it starts all necessary services and does its job as configured. It might be hard to believe, but we want to fight that inclination for two important reasons:

  • Pacemaker is a state machine
  • Pacemaker needs total control of any service it manages

Pacemaker wants to start services itself so it knows that the current status is the one it created. It will perform tests to obtain this information, but for things such as DRBD, this isn't always reliable. It's generally safer to start from scratch. Beyond this, if a service that isn't supposed to be running starts, Pacemaker will only have to stop it anyway.

In this recipe, we'll quickly cover which services to disable on each of our PostgreSQL nodes.

Getting ready

As we're continuing to configure Corosync and Pacemaker, make sure you've followed all the previous recipes.

How to do it...

For this recipe, we will use the...