Contributors: ryan, sivel, tott Tags: cache, memcached Requires at least: 3.0 Tested up to: 3.7.1 Stable tag: 2.1

Use memcached and the PECL memcache extension to provide a backing store for the WordPress object cache.

Memcached Object Cache provides a persistent backend for the WordPress object cache. A memcached server and the PECL memcache extension are required.

1. Install memcached on at least one server. Note the connection info. The default is 127.0.0.1:11211.

2. Install the PECL memcache extension

3. Copy object-cache.php to wp-content

Add something similar to the following to wp-config.php above /* That's all, stop editing! Happy blogging. */:

$memcached_servers = array(
	'default' => array(
		'10.10.10.20:11211',
		'10.10.10.30:11211'
	)
);

The top level array keys, are cache groups, where 'default' corresponds to any cache group that is not explicitly defined. This allows for specifying memcached servers that only handle certain cache groups. The most common use is only specifying 'default'.

Possible cache groups are:

{$taxonomy}_relationships
{$meta_type}_meta
{$taxonomy}_relationships
blog-details
blog-id-cache
blog-lookup
bookmark
calendar
category
comment
counts
general
global-posts
options
plugins
post_ancestors
post_meta
posts
rss
site-lookup
site-options
site-transient
terms
themes
timeinfo
transient
user_meta
useremail
userlogins
usermeta
users
userslugs
widget

• For debugging purposes the following debug parameters can be used
  • ?memcache=skip would skip memcache and fallback to regular cache class
  • ?memcache=wipe-page-cache would delete each key before trying to get it.
• Set WP_CACHE_KEY_SALT to DB_NAME by default to ensure that multiple installs on one server won't overlap
• You can define the memcache parameters used for skip/wipe adding define( 'WP_CACHE_SECRET_KEY_SKIP', '' ); define( 'WP_CACHE_SECRET_KEY_WIPE', '' ); to your wp-config.php (functions.php would be to late).
• Added a simple admin bar menu

• Break references by cloning objects
• Keep local cache in sync with memcached when using incr and decr
• Handle limited environments where is_multisite() is not defined
• Fix setting and getting 0
• PHP 5.2.4 is now required
• Use the WP_CACHE_KEY_SALT constant if available to gaurantee uniqueness of keys