Book Image

Redis Essentials

Book Image

Redis Essentials

Overview of this book

Redis is the most popular in-memory key-value data store. It's very lightweight and its data types give it an edge over the other competitors. If you need an in-memory database or a high-performance cache system that is simple to use and highly scalable, Redis is what you need. Redis Essentials is a fast-paced guide that teaches the fundamentals on data types, explains how to manage data through commands, and shares experiences from big players in the industry. We start off by explaining the basics of Redis followed by the various data types such as Strings, hashes, lists, and more. Next, Common pitfalls for various scenarios are described, followed by solutions to ensure you do not fall into common traps. After this, major differences between client implementations in PHP, Python, and Ruby are presented. Next, you will learn how to extend Redis with Lua, get to know security techniques such as basic authorization, firewall rules, and SSL encryption, and discover how to use Twemproxy, Redis Sentinel, and Redis Cluster to scale infrastructures horizontally. At the end of this book, you will be able to utilize all the essential features of Redis to optimize your project's performance.
Table of Contents (17 chapters)
Redis Essentials
Credits
About the Authors
Acknowledgments
About the Reviewers
www.PacktPub.com
Preface
5
Clients for Your Favorite Language (Become a Redis Polyglot)
Index

Using Swap


There is a Linux kernel parameter called swappiness that controls when the operating system will start using the swap space. This parameter can be set to values between 0 and 100. A lower value tells the kernel to use the swap space less frequently, and a higher value tells it to use the swap space more frequently. The default value is 60.

Here are some special cases of using swaps:

Value

Strategy

vm.swappiness = 0

  • Linux 3.5 and newer: Disables swap entirely

  • Linux 3.4 and older: Swap only to avoid an "out of memory" condition

vm.swappiness = 1

  • Linux 3.5 and newer: Minimum amount of swapping without disabling it entirely

vm.swappiness = 100

  • Linux will swap aggressively

In a scenario where Redis needs to access from the swap space, the OS needs to move the necessary pages back into the RAM. During this process, Redis is blocked until the OS finishes its job.

We recommend that you use a swappiness of 0 when your data always fits into the RAM and 1 when you are not sure...