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

Testing a write query on pgpool

The load-balancing mode in pgpool presumably distributes connections according to server weight. Then, master/slave mode defines which servers are read-only as opposed to writable.

But can we depend on this behavior? We should at least verify these claims before using such a configuration in a production environment. Our uptime depends upon it.

Getting ready

Make sure pgpool is installed and configured according to the Installing pgpool and Configuring pgpool for master/slave mode recipes. We will follow these two recipes by testing a pool setup with write activity, so we need a fully functional pgpool environment.

To simplify this recipe, perform all the tests as the postgres system user. To facilitate this, we may need to set all the pg_hba.conf authentication types to trust, though we strongly suggest user and password combinations instead.

If our primary PostgreSQL server is on, we can connect to pgpool by using port 9999. With psql, we can connect...