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

Detaching a problematic node

There's one last thing we need to cover before ending this chapter. If a server is causing problems, there's a good chance that the infrastructure department will want to reclaim, rebuild, or replace it. Simply stopping the broken server is a possible solution, but there is a safer way to decouple DRBD from another system.

In this recipe, we'll quickly cover partially dismantling a running DRBD system without disrupting the active server.

Getting ready

By now, we need the full stack and probably a fully active database server as well. Follow all the recipes up to Tweaking XFS performance before starting here.

How to do it...

For this recipe, we will need two PostgreSQL servers: pg1 and pg2, where pg1 is the currently active node. Follow these steps as the root user on the system indicated to permanently remove pg2 from the DRBD cluster:

  1. Execute this command on both pg1 and pg2 to disconnect DRBD:
drbdadm disconnect pg
  1. Invalidate the data on the remote node with drbdadm...