1 memcached support for MediaWiki:
3 From ca August 2003, MediaWiki has optional support for memcached, a
4 "high-performance, distributed memory object caching system".
5 For general information on it, see: http://www.danga.com/memcached/
7 Memcached is likely more trouble than a small site will need, but
8 for a larger site with heavy load, like Wikipedia, it should help
9 lighten the load on the database servers by caching data and objects
14 * PHP must be compiled with --enable-sockets
16 * libevent: http://www.monkey.org/~provos/libevent/
17 (as of 2003-08-11, 0.7a is current)
19 * optionally, epoll-rt patch for Linux kernel:
20 http://www.xmailserver.org/linux-patches/nio-improve.html
22 * memcached: http://www.danga.com/memcached/download.bml
23 (as of this writing, 1.1.9 is current)
25 Memcached and libevent are under BSD-style licenses.
27 The server should run on Linux and other Unix-like systems... you
28 can run multiple servers on one machine or on multiple machines on
29 a network; storage can be distributed across multiple servers, and
30 multiple web servers can use the same cache cluster.
32 ********************* W A R N I N G ! ! ! ! ! ***********************
33 Memcached has no security or authentication. Please ensure that your
34 server is appropriately firewalled, and that the port(s) used for
35 memcached servers are not publicly accessible. Otherwise, anyone on
36 the internet can put data into and read data from your cache.
38 An attacker familiar with MediaWiki internals could use this to give
39 themselves developer access and delete all data from the wiki's
40 database, as well as getting all users' password hashes and e-mail
42 ********************* W A R N I N G ! ! ! ! ! ***********************
46 If you want to start small, just run one memcached on your web
49 memcached -d -l 127.0.0.1 -p 11000 -m 64
51 (to run in daemon mode, accessible only via loopback interface,
52 on port 11000, using up to 64MB of memory)
54 In your LocalSettings.php file, set:
56 $wgMainCacheType = CACHE_MEMCACHED;
57 $wgMemCachedServers = array( "127.0.0.1:11000" );
59 The wiki should then use memcached to cache various data. To use
60 multiple servers (physically separate boxes or multiple caches
61 on one machine on a large-memory x86 box), just add more items
62 to the array. To increase the weight of a server (say, because
63 it has twice the memory of the others and you want to spread
64 usage evenly), make its entry a subarray:
66 $wgMemCachedServers = array(
67 "127.0.0.1:11000", # one gig on this box
68 array("192.168.0.1:11000", 2 ) # two gigs on the other box
71 == PHP client for memcached ==
73 As of this writing, MediaWiki includes version 1.0.10 of the PHP
74 memcached client by Ryan Gilfether <hotrodder@rocketmail.com>.
75 You'll find some documentation for it in the 'php-memcached'
76 subdirectory under the present one.
78 We intend to track updates, but if you want to check for the lastest
79 released version, see http://www.danga.com/memcached/apis.bml
81 MediaWiki use three object for memcaching:
82 * $wgMemc, controlled by $wgMainCacheType
83 * $parserMemc, controlled by $wgParserCacheType
84 * $messageMemc, controlled by $wgMessageCacheType
85 If you set CACHE_NONE to one of the three control variable, (default
86 value for $wgMainCacheType), MediaWiki still create a MemCacheClient,
87 but requests to it are no-ops and we always fall through to the
88 database. If the cache daemon can't be contacted, it should also
89 disable itself fairly smoothly.
91 By default, $wgMemc is used but when it is $parserMemc or $messageMemc
92 this is mentionned below.
97 key: $wgDBname:ajaxsearch:md5( $search )
98 ex: wikidb:ajaxsearch:9565814d5d564fa898dd6111b94fae0b
99 stores: array with the result of research of a given text
104 key: $wgDBname:dateformatter
105 ex: wikidb:dateformatter
106 stores: a single instance of the DateFormatter class
111 key: $wgDBname:diff:version:{MW_DIFF_VERSION}:oldid:$old:newid:$new
112 ex: wikidb:diff:version:1.11a:oldid:1:newid:2
113 stores: body of a difference
118 key: $wgDBname:interwiki:$prefix
119 ex: wikidb:interwiki:w
120 stores: object from the interwiki table of the database
121 expiry: $wgInterwikiExpiry
124 Lag time of the databases:
125 key: $wgDBname:lag_times
127 stores: array mapping the database id to its lag time
132 key: $wgDBname:localisation:$lang
133 ex: wikidb:localisation:de
134 stores: array of localisation settings
135 set in: Language::loadLocalisation()
137 cleared by: Language::loadLocalisation()
140 stored in: $parserMemc
141 key: $wgDBname:messages, $wgDBname:messages-hash, $wgDBname:messages-status
142 ex: wikidb:messages, wikidb:messages-hash, wikidb:messages-status
143 stores: an array where the keys are DB keys and the values are messages
144 set in: wfMsg(), Article::editUpdates() both call wfLoadAllMessages()
145 expriy: $wgMsgCacheExpiry
149 key: $wgDBname:newtalk:ip:$ip
150 ex: wikidb:newtalk:ip:123.45.67.89
151 stores: integer, 0 or 1
152 set in: User::loadFromDatabase()
153 cleared by: User::saveSettings() # ?
157 stored in: $parserMemc
158 controlled by: $wgEnableParserCache
159 key: $wgDBname:pcache:idhash:$pageid-$renderkey!$hash$edit
160 $pageid: id of the page
161 $renderkey: 1 if action=render, 0 otherwise
162 $hash: hash of user options, see User::getPageRenderingHash()
163 $edit: '!edit=0' if the user can't edit the page, '' otherwise
164 ex: wikidb:pcache:idhash:1-0!1!0!!en!2
165 stores: ParserOutput object
166 modified by: Article::editUpdates()
167 expriy: $wgParserCacheExpireTime or one hour if it contains specific magic
171 controlled by: $wgRateLimits
172 key: $wgDBname:limiter:action:$action:ip:$ip,
173 $wgDBname:limiter:action:$action:user:$id,
174 mediawiki:limiter:action:$action:ip:$ip and
175 mediawiki:limiter:action:$action:subnet:$sub
176 ex: wikidb:limiter:action:edit:ip:123.45.67.89,
177 wikidb:limiter:action:edit:user:1012
178 mediawiki:limiter:action:edit:ip:123.45.67.89 and
179 mediawiki:limiter:action:$action:subnet:123.45.67
180 stores: number of action made by user/ip/subnet
182 expiry: expiry set for the action and group in $wgRateLimits
185 Proxy Check: (deprecated)
186 key: $wgDBname:proxy:ip:$ip
187 ex: wikidb:proxy:ip:123.45.67.89
188 stores: 1 if the ip is a proxy
190 expiry: $wgProxyMemcExpiry
193 key: $wgDBname:revisiontext:textid:$id
194 ex: wikidb:revisiontext:textid:1012
195 stores: text of a revision
197 expriry: $wgRevisionCacheExpiry
200 controlled by: $wgSessionsInMemcached
201 key: $wgBDname:session:$id
202 ex: wikidb:session:38d7c5b8d3bfc51egf40c69bc40f8be3
203 stores: $SESSION, useful when using a multi-sever wiki
205 cleared by: session_destroy()
208 stored in: $parserMemc
209 controlled by: $wgEnableSidebarCache
210 key: $wgDBname:sidebar
212 stores: the html output of the sidebar
213 expriy: $wgSidebarCacheExpiry
214 cleared by: MessageCache::replace()
217 key: $wgDBname:allpages:ns:$ns
218 ex: wikidb:allpages:ns:0
219 stores: array of pages in a namespace
223 Special:Recentchanges (feed):
224 stored in: $messageMemc
225 key: $wgDBname:rcfeed:$format:limit:$imit:minor:$hideminor and
226 rcfeed:$format:timestamp
227 ex: wikidb:rcfeed:rss:limit:50:minor:0 and rcfeed:rss:timestamp
228 stores: xml output of feed
230 clear by: calling Special:Recentchanges?action=purge
233 controlled by: $wgStatsMethod
234 key: $wgDBname:stats:$key
235 ex: wikibd:stats:request_with_session
236 stores: counter for statistics (see maintenance/stats.php script)
238 cleared by: maintenance/clear_stats.php script
241 key: $wgDBname:user:id:$sId
242 ex: wikidb:user:id:51
243 stores: instance of class User
244 set in: User::saveToCache()
245 cleared by: User::saveSettings(), User::clearSharedCache()