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

Installing and configuring walctl

There's something to be said for simplicity. So far, the tools we've discussed in this chapter are larger client-server mechanisms or components of entire toolkits. One of the central tenets of the Unix philosophy is to build tools that do one thing well. In this case, we turn to Peak6 and their walctl WAL-management tools.

I created walctl specifically to address shortcomings in existing WAL-related utilities. Primarily of note is the question of architecture. Existing WAL tools follow an architecture diametrically opposed to the end goal of high availability. We often see this:

In this kind of model, the master node is tasked with transmitting transaction streams or WAL files to every node in the cluster. This makes it fantastically difficult to change the active master node and potentially overloads the master node itself. The primary write node of any cluster should be focused on fulfilling client requests. The purpose of walctl is to impose a structure...