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 a node back into the cluster

Recovering systems after a major crash or outage is not an enjoyable experience. We must reboot or restore one or more servers, perform forensics to determine the root cause of the failure, and attempt to repair or replace corrupt binaries.

This is no less true on systems that rely on Patroni as their high availability solution. However, Patroni automates the more annoying portions of recovering a damaged PostgreSQL database.

Let's see how.

Getting ready

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

We also need a broken server. The easiest way to do this is to break it ourselves. Execute these commands on any system to simulate an unrecoverable server crash:

pkill -9 patronipkill -9 postgresfind /db/pgdata -name '*r*' -o  -name '*0*' -delete

How to do it...

For this recipe, we should already have three PostgreSQL servers. As before, we'll assume they are named pg1, pg2, and pg3...