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

Swapping active nodes with repmgr

Creating a clone can be surprisingly dangerous. When using a utility such as rsync, accidentally transposing the source and target can result in erasing the source PostgreSQL data directory. This is especially true when swapping from one node to another and then reversing the process. It's all too easy to accidentally invoke the wrong script when the source and target are so readily switched.

We've already established how repmgr can ease the process of clone creation, and now it's time to discuss node promotion. There are two questions we will answer in this recipe. How do we swap from one active PostgreSQL node to another? How do we then reactivate the original node without risking our data? The second question is perhaps more important due to the fact that we are at reduced capacity following node deactivation.

Let's explore how to keep our database available through multiple node swaps.

Getting ready

This recipe depends on repmgr being installed on both a...