Manual:$wgMemCachedServers

Memcached settings: $wgMemCachedServers
Memcached servers
Introduced in version:Before 1.1.0
Removed in version:Still in use
Allowed values:Unspecified
Default value:[ '127.0.0.1:11211', ] (1.22+)
array( '127.0.0.1:11000' ) (1.1-1.21)

Array of memcached network servers, or unix socket pathnames using the PHP form (example) unix:///var/run/memcached/socket (for use with the memcached memory-based object store).

Note that beginning in MediaWiki 1.35.6, 1.36.4 and 1.37.2, when specifying a unix socket pathname, a trailing :port number must not be specified. It was ignored by the prior versions, but is now treated as part of the pathname.

Details

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To use multiple servers (physically separate boxes or multiple caches on one machine on a large-memory x86 box), just add more items to the array. To increase the weight of a server (say, because it has twice the memory of the others and you want to spread usage evenly), make its entry a subarray:

$wgMemCachedServers = [
  "127.0.0.1:11211", # one gig on this box
  [ "192.168.0.1:11211", 2 ] # two gigs on the other box
];

You can have multiple wikis point to the same Memcached server, as long as each have different wiki-ids ($wgDBname ). Certain cache keys are intentionally shared in such a scenario, such as rate limiting stuff.

More information in docs/memcached.md.