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

Reducing contention with concurrent indexes

When administering a PostgreSQL installation, we will eventually need to create new tables and indexes. In the case of new indexes, the table is locked in shared exclusive access mode for the duration of the creation process, blocking any insert, update, or delete activity. This both prevents inconsistencies, and allows the database to modify the table structure to reflect the new index.

Unfortunately, this process is fundamentally incompatible with maintaining a highly-available server. While building the index, PostgreSQL needs to examine every valid table row, which means loading it from the disk into memory. For large or active tables, this can cause excessive strain on the system. Other database activities will reduce available disk bandwidth, and the required lock will block all modifications of data in that table. Combined, this can lead to a table being locked for a very long time.

Beginning with PostgreSQL 8.2, indexes can be created concurrently...