Redis Object Cache for WordPress

A persistent object cache backend powered by Redis. Supports HHVM's Redis extension, the PECL Redis Extension and the Predis library for PHP.

Forked from Eric Mann's and Erick Hitter's Redis Object Cache.

Installation

For detailed installation instructions, please read the standard installation procedure for WordPress plugins.

1. Make sure Redis in installed and running.
2. Install and activate plugin.
3. Enable the object cache under Settings -> Redis.
4. If necessary, adjust connection parameters.

If you server doesn't support the WordPress Filesystem API, you have to manually copy the object-cache.php file from the /plugins/redis-cache/includes/ directory to the /wp-content/ directory.

Connection Parameters

By default the object cache drop-in will connect to Redis over TCP at 127.0.0.1:6379 and select database 0.

To adjust the connection parameters, define any of following constants in your wp-config.php file.

• WP_REDIS_CLIENT (default: not set)

  Specifies the client used to communicate with Redis. Supports hhvm, pecl and predis.

• WP_REDIS_SCHEME (default: tcp)

  Specifies the protocol used to communicate with an instance of Redis. Internally the client uses the connection class associated to the specified connection scheme. Supports tcp (TCP/IP), unix (UNIX domain sockets) or http (HTTP protocol through Webdis).

• WP_REDIS_HOST (default: 127.0.0.1)

  IP or hostname of the target server. This is ignored when connecting to Redis using UNIX domain sockets.

• WP_REDIS_PORT (default: 6379)

  TCP/IP port of the target server. This is ignored when connecting to Redis using UNIX domain sockets.

• WP_REDIS_PATH (default: not set)

  Path of the UNIX domain socket file used when connecting to Redis using UNIX domain sockets.

• WP_REDIS_DATABASE (default: 0)

  Accepts a numeric value that is used to automatically select a logical database with the SELECT command.

• WP_REDIS_PASSWORD (default: not set)

  Accepts a value used to authenticate with a Redis server protected by password with the AUTH command.

Configuration Parameters

To adjust the configuration, define any of the following constants in your wp-config.php file.

• WP_CACHE_KEY_SALT [default: not set]

  Set the prefix for all cache keys. Useful in setups where multiple installs share a common wp-config.php or $table_prefix, to guarantee uniqueness of cache keys.

• WP_REDIS_MAXTTL (default: not set)

  Set maximum time-to-live (in seconds) for cache keys with an expiration time of 0.

Replication & Clustering

To use Replication and Clustering, make sure your server is running PHP7, your setup is using Predis to connect to Redis and you consulted the Predis documentation.

For replication, use the WP_REDIS_SERVERS constant and for clustering the WP_REDIS_CLUSTER constant. You can use a named array or an URI string to specify the parameters.

Master-Slave Replication

define( 'WP_REDIS_SERVERS', [
    'tcp://127.0.0.1:6379?database=15&alias=master',
    'tcp://127.0.0.2:6379?database=15&alias=slave-01',
] );

Clustering via Client-side Sharding

define( 'WP_REDIS_CLUSTER', [
    'tcp://127.0.0.1:6379?database=15&alias=node-01',
    'tcp://127.0.0.2:6379?database=15&alias=node-02',
] );