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Redis Object Cache for WordPress

A persistent object cache backend powered by Redis®¹. Supports Predis, PhpRedis (PECL), Relay, replication, sentinels, clustering and WP-CLI.

Redis Object Cache screenshots

Object Cache Pro

A business class Redis®¹ object cache backend. Truly reliable, highly optimized, fully customizable and with a dedicated engineer when you most need it.

  • Rewritten for raw performance
  • 100% WordPress API compliant
  • Faster serialization and compression
  • Easy debugging & logging
  • Cache prefetching and advanced analytics
  • Fully unit tested (100% code coverage)
  • Optimized for WooCommerce, Jetpack & Yoast SEO
  • And much more...

Installation

To get started, please see the installation instructions.

FAQ & Troubleshooting

Answers to common questions and troubleshooting of common errors can be found in the FAQ.

Configuration

The Redis Object Cache plugin comes with vast set of configuration options. If you're unsure how to use them read the installation instructions.

Configuration constant Default Description
WP_REDIS_HOST 127.0.0.1 The hostname of the Redis server
WP_REDIS_PORT 6379 The port of the Redis server
WP_REDIS_PATH The path to the unix socket of the Redis server
WP_REDIS_SCHEME tcp The scheme used to connect: tcp or unix
WP_REDIS_DATABASE 0 The database used by the cache: 0-15
WP_REDIS_PREFIX The prefix used for all cache keys to avoid data collisions (replaces WP_CACHE_KEY_SALT), should be human readable and not a "salt"
WP_REDIS_PASSWORD The password of the Redis server, supports Redis ACLs arrays: ['user', 'password']
WP_REDIS_MAXTTL 0 The maximum time-to-live of cache keys
WP_REDIS_CLIENT The client used to communicate with Redis (defaults to phpredis when installed, otherwise predis), supports phpredis, predis, relay
WP_REDIS_TIMEOUT 1 The connection timeout in seconds
WP_REDIS_READ_TIMEOUT 1 The timeout in seconds when reading/writing
WP_REDIS_IGNORED_GROUPS [] Groups that should not be cached between requests in Redis
Advanced configuration options
Configuration constant Default Description
WP_CACHE_KEY_SALT Deprecated. Replaced by WP_REDIS_PREFIX
WP_REDIS_FLUSH_TIMEOUT 5 Experimental. The timeout in seconds when flushing
WP_REDIS_RETRY_INTERVAL The number of milliseconds between retries (PhpRedis only)
WP_REDIS_GLOBAL_GROUPS [] Additional groups that are considered global on multisite networks
WP_REDIS_METRICS_MAX_TIME 3600 The maximum number of seconds metrics should be stored
WP_REDIS_IGBINARY false Whether to use the igbinary PHP extension for serialization
WP_REDIS_DISABLED false Emergency switch to bypass the object cache without deleting the drop-in
WP_REDIS_DISABLE_ADMINBAR false Disables admin bar display
WP_REDIS_DISABLE_METRICS false Disables metrics collection and display
WP_REDIS_DISABLE_BANNERS false Disables promotional banners
WP_REDIS_DISABLE_DROPIN_CHECK false Disables the extended drop-in write test
WP_REDIS_DISABLE_DROPIN_AUTOUPDATE false Disables the drop-in auto-update
WP_REDIS_SSL_CONTEXT [] TLS connection options for tls or rediss scheme
Unsupported configuration options

Options that exist, but should not, may break without notice in future releases and won't receive any support whatsoever from our team:

Configuration constant Default Description
WP_REDIS_GRACEFUL false Prevents exceptions from being thrown, but will cause data corruption
WP_REDIS_SELECTIVE_FLUSH false Uses terribly slow Lua script for flushing
WP_REDIS_UNFLUSHABLE_GROUPS [] Uses terribly slow Lua script to prevent groups from being flushed

Connections

Connecting over Unix socket 
define( 'WP_REDIS_SCHEME', 'unix' );
define( 'WP_REDIS_PATH', '/var/run/redis.sock' );
Connecting over TCP+TLS 
define( 'WP_REDIS_SCHEME', 'tls' );
define( 'WP_REDIS_HOST', 'master.ncit.ameaqx.use1.cache.amazonaws.com' );
define( 'WP_REDIS_PORT', 6379 );

Additional TLS/SSL stream connection options for connections can be defined using WP_REDIS_SSL_CONTEXT:

define( 'WP_REDIS_SSL_CONTEXT', [
    'verify_peer' => false,
    'verify_peer_name' => false,
]);
Connecting using ACL authentication 
define( 'WP_REDIS_PASSWORD', [ 'username', 'password' ] );

Scaling

Redis Object Cache offers various replication, sharding, cluster and sentinel setups to users with advanced technical knowledge of Redis and PHP, that have consulted the Predis, PhpRedis or Relay documentation.

Relay

Relay is a next-generation cache that keeps a partial replica of Redis' dataset in PHP's memory for ridiculously fast lookups, especially when Redis Server is not on the same machine as WordPress.

define( 'WP_REDIS_CLIENT', 'relay' );

define( 'WP_REDIS_HOST', '127.0.0.1' );
define( 'WP_REDIS_PORT', 6379 );

// when using Relay, each WordPress installation
// MUST a dedicated Redis database and unique prefix
define( 'WP_REDIS_DATABASE', 0 );
define( 'WP_REDIS_PREFIX', 'db3:' );

// consume less memory
define( 'WP_REDIS_IGBINARY', true );
Replication

https://redis.io/docs/management/replication/

define( 'WP_REDIS_CLIENT', 'predis' );

define( 'WP_REDIS_SERVERS', [
    'tcp://127.0.0.1:6379?database=5&role=master',
    'tcp://127.0.0.2:6379?database=5&alias=replica-01',
] );
Sharding

This is a PhpRedis specific feature using RedisArray.

define( 'WP_REDIS_CLIENT', 'phpredis' );

define( 'WP_REDIS_SHARDS', [
    'tcp://127.0.0.1:6379?database=10&alias=shard-01',
    'tcp://127.0.0.2:6379?database=10&alias=shard-02',
    'tcp://127.0.0.3:6379?database=10&alias=shard-03',
] );
Redis Sentinel

https://redis.io/docs/management/sentinel/

define( 'WP_REDIS_CLIENT', 'predis' );

define( 'WP_REDIS_SENTINEL', 'my-sentinel' );
define( 'WP_REDIS_SERVERS', [
    'tcp://127.0.0.1:5380',
    'tcp://127.0.0.2:5381',
    'tcp://127.0.0.3:5382',
] );
Redis Cluster

https://redis.io/docs/management/scaling/

define( 'WP_REDIS_CLIENT', 'phpredis' );

define( 'WP_REDIS_CLUSTER', [
    'tcp://127.0.0.1:6379?alias=node-01',
    'tcp://127.0.0.2:6379?alias=node-02',
    'tcp://127.0.0.3:6379?alias=node-03',
] );

WP CLI commands

Redis Object Cache has various WP CLI commands, for more information run wp help redis.

Command Description
wp redis status Shows the object cache status and diagnostics
wp redis enable Enables the object cache
wp redis disable Disables the object cache
wp redis update-dropin Updates the object cache drop-in

Actions & Filters

Redis Object Cache has various hooks and the commonly used ones are listed below.

Filter / Action Description
redis_cache_expiration Filters the cache expiration for individual keys
redis_cache_validate_dropin Filters whether the drop-in is valid
redis_cache_add_non_persistent_groups Filters the groups to be marked as non persistent

Footnotes

¹ Redis is a registered trademark of Redis Ltd. Any rights therein are reserved to Redis Ltd. Any use by Redis Object Cache is for referential purposes only and does not indicate any sponsorship, endorsement or affiliation between Redis and Redis Object Cache.