Overview

A WordPress object cache backend that implements all available methods using the Redis PECL library.

Authors

• Eric Mann
• Erick Hitter
• Tuan Duong

Installation

1. Install and configure Redis. There is a good tutorial here.
2. Install the Redis PECL module.
3. Add object-cache.php to the wp-content directory. It is a drop-in file, not a plugin, so it belongs in the wp-content directory, not the plugins directory.
4. By default, the script will connect to Redis at 127.0.0.1:6379. See the Connecting to Redis section for further options.

Connecting to Redis

By default, the plugin uses 127.0.0.1 and 6379 as the default host and port when creating a new client instance; the default database of 0 is also used. Three constants are provided to override these default values.

Specify WP_REDIS_BACKEND_HOST, WP_REDIS_BACKEND_PORT, and WP_REDIS_BACKEND_DB to set the necessary, non-default connection values for your Redis instance.

Prefixing Cache Keys

The constant WP_CACHE_KEY_SALT is provided to add a prefix to all cache keys used by the plugin. If running two single instances of WordPress from the same Redis instance, this constant could be used to avoid overlap in cache keys. Note that special handling is not needed for WordPress Multisite.

In-memory cache support

It's disabled by default. Define WP_INNER_CACHE to enable this feature

define('WP_INNER_CACHE', true)

When this feature is enabled, cache data will be stored into PHP variable $wp_inner_cache, to avoid getting same redis key many times and save ton of requests to Redis

• Please ensure your PHP memory setting is enough for this feature or you have to write addition code to limit the $wp_inner_cache by $group and $key