FAQ: Installation: Redis Server

Installation Instructions

Summary:

This document will walk through the setup and configuration of enabling Redis in your Wordpress environment.

Redis Setup

Redis is a very performant solution to give your site a quick speed boost and doesn't require much effort.

Enabling Redis cache support

• Make sure that the redis server is accessible from the web application servers
  • Redis installation instructions: https://redis.io/topics/quickstart
  • If installing redis on a dedicated server, make sure that the web application servers have access to TCP Port 6379
  • Add the following at the end of your /etc/redis/redis.conf config file

    maxmemory 2048mb  # This should be 50% of your available RAM in the node 
    maxmemory-policy allkeys-lru
    

• Add the following in the db-config.php file in the ini directory of the w3-total-cache plugin directory

  //
  // redis config cache
  //
  define( 'W3TC_CONFIG_CACHE_ENGINE', 'redis');
  define( 'W3TC_CONFIG_CACHE_REDIS_SERVERS', 'redis_hostname::6379' );
  
  // optional redis settings
  define( 'W3TC_CONFIG_CACHE_REDIS_PERSISTENT', true );
  define( 'W3TC_CONFIG_CACHE_REDIS_DBID', 0 );
  define( 'W3TC_CONFIG_CACHE_REDIS_PASSWORD', '' );
  

• Enable the following in the Performance menu in the WP Admin
  • General > Page Cache > Redis -- This provides the most bang for the buck
  • General > Database Cache > Redis
  • General > Object Cache > Redis

Performance Testing results

Environment Setup

• docker
• php-fpm 7.2
• nginx
• mariadb 10.1
• redis 4.0
• siege
• WP Plugin: Export All Posts
• wptest.io sample content
• MacOS High Sierra
• 512GB SSD w/ 16GB RAM
• IntelliJ 2017.03

Object and Database Cache enabled 5 minute run:

Transactions:		        1441 hits
Availability:		      100.00 %
Elapsed time:		      250.83 secs
Data transferred:	       87.08 MB
Response time:		        2.12 secs
Transaction rate:	        5.74 trans/sec
Throughput:		        0.35 MB/sec
Concurrency:		       12.19
Successful transactions:        1362
Failed transactions:	           0
Longest transaction:	        5.93
Shortest transaction:	        0.49

Page, Object and Database Cache enabled for 10 minute run:

Transactions:		       13862 hits
Availability:		      100.00 %
Elapsed time:		      563.31 secs
Data transferred:	      291.82 MB
Response time:		        0.11 secs
Transaction rate:	       24.61 trans/sec
Throughput:		        0.52 MB/sec
Concurrency:		        2.73
Successful transactions:       13107
Failed transactions:	           0
Longest transaction:	        1.03
Shortest transaction:	        0.06

Redis Socket Support

W3 Total Cache supports Redis Unix socket. All you need to replace the default hostname with a Redis Unix socket (usually /var/run/redis/redis.sock or /var/run/redis/redis.sock:0) as shown in the example below (Please note that the screenshot shows Memcached, however, the procedure is same)