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

Managing WAL files with walctl

The walctl toolkit provides two extra scripts that a DBA should never have to call manually: walctl_push and walctl_pull. These are purely intended to facilitate the preferred architecture of walctl. However, we also understand that many PostgreSQL servers exist already, and not every cluster is new.

It's actually very likely that at least one clone exists now and that such behavior is directly supported by PostgreSQL 9.1 and more. In this recipe, we'll explore how to convert an existing cluster to use walctl for WAL management instead.

Getting ready

This recipe depends on walctl being installed on a primary server and any existing PostgreSQL clones. Please follow the Installing and configuring walctl recipe before continuing.

How to do it...

For this recipe, imagine we have four PostgreSQL servers. The primary PostgreSQL server is pg-primary, and we also have three existing replicas named pg-clone1, pg-clone2, and pg-clone3. Execute this command as the postgres...