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

Terminating rogue connections

There comes a time in every DBA's life when they must disconnect a PostgreSQL client from the server; for us, that time is now. There are varying degrees of escalation available for this purpose, and several system catalog views to provide viable targets. Why would we want to forcefully cancel a query or disconnect a user?

To prevent utter havoc, should a user forget an important clause, a query could require several hours to complete. During this time, it is consuming an entire CPU and saturating the storage bandwidth while doing so. A buggy application could start a transaction and stop responding, leaving an idle transaction potentially holding locks and causing a wait backlog.

There are many reasons to evict a connection, and most of them revolve around maintaining a regular flow of queries. If we're unable to maintain low latency and high throughput, our work in building a highly-available environment is wasted.

Getting ready

Luckily, PostgreSQL provides most...