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

Adding DRBD to cluster management

DRBD is actually one of the most difficult resources to manage with Pacemaker. Unlike a regular service that is started or stopped depending on where it is active, DRBD is always active. The only thing that changes between two nodes running DRBD is the Primary or Secondary state ascribed to each.

Due to this complication, DRBD is not one resource, but two:

  • A DRBD resource to manage starting and stopping DRBD
  • A master/slave resource to control which node acts as the Primary

In this recipe, we'll allocate both of these resources so that Pacemaker can manage DRBD properly.

Getting ready

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

How to do it...

In the previous chapter, we created a DRBD resource named pg. With this in mind, follow these steps as the root user to add DRBD to Pacemaker:

  1. Create a basic Pacemaker primitive for DRBD with this command:
crm configure primitive drbd_pg ocf:linbit:drbd \        params drbd_resource...