Wikimedia servers

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Wikipedia and the other Wikimedia projects are run from several racks full of servers. See also Wikimedia's technical blog.

System architecture[edit]

Network topology[edit]

The Network topology is described in the article Server layout diagrams.

Software[edit]

Simplified overview of the employed software as of October 2015. (A very complex LAMP "stack")
  • Our DNS servers run gdnsd. We use geographical DNS to distribute requests between our four data centers (3x US, 1x Europe) depending on the location of the client.
  • We use Linux Virtual Server (LVS) on commodity servers to load balance incoming requests. LVS is also used as an internal load balancer to distribute MediaWiki requests. For back end monitoring and failover, we have our own system called PyBal.
  • For regular MediaWiki web requests (articles/API) we use Varnish caching proxy servers in front of Apache HTTP Server.
  • All our servers run either Ubuntu Server or Debian.
  • For distributed object storage we use Swift.
  • Our main web application is MediaWiki, which is written in PHP (~70 %) and JavaScript (~30 %).[1]
  • Our structured data is stored in MariaDB.[2] We group wikis into clusters, and each cluster is served by several MariaDB servers, replicated in a single-master configuration.
  • We use Memcached for caching of database query and computation results.
  • For full-text search we use Elasticsearch (Extension:CirrusSearch).
  • https://noc.wikimedia.org/conf/ - Wikimedia configuration files.

Hosting[edit]

Diagram showing flow of data between Wikipedia's servers. Twenty database servers talk to hundreds of Apache servers in the backend; the Apache servers talk to fifty squids in the frontend.
Overview of system architecture
Wikimedia server racks at CyrusOne
See also: wikitech:Clusters

As of October 2014, we have the following colocation facilities (the name is derived from an acronym of the facility's company and acronym of nearby airport):

eqiad 
Equinix in Ashburn, Virginia.
esams 
EvoSwitch in Amsterdam, the Netherlands (cache).
knams 
Kennisnet in Amsterdam, the Netherlands (networking for the above).
ulsfo 
United Layer in San Francisco (cache; USA West and East Asia).
codfw 
CyrusOne in Carrollton, Texas.

The backend web and database servers are in Ashburn, with Carrollton to handle emergency fallback in the future. Carrollton was chosen for this as a result of the 2013 Datacenter RfC. At EvoSwitch, we have a Varnish cache cluster and several miscellaneous servers. The Kennisnet location is now used only for network access and routing.

Ashburn (eqiad) became the primary data center in January 2013, taking over from Tampa (pmtpa and sdtpa) which had been the main data centre since 2004. Around April 2014, sdtpa (Equinix - formerly Switch and Data - in Tampa, Florida, provided networking for pmtpa) was shut down, followed by pmtpa (Hostway - formerly PowerMedium - in Tampa, Florida) in October 2014.

In the past we've had other caching locations like Seoul (yaseo, Yahoo!) and Paris (lopar, Lost Oasis); the WMF 2010-2015 strategic plan reach target includes «additional caching centers in key locations to manage increased traffic from Latin America, Asia and the Middle East, as well as to ensure reasonable and consistent load times no matter where a reader is located».

EvoSwitch and Kennisnet are recognised as benefactors for their in-kind donations. See the current list of benefactors.

A list of servers and their functions used to be available at the server roles page; no such list is currently maintained publicly (perhaps the private racktables tool has one). It's however possible to see a compact table of all servers grouped by type on icinga (click to have a list of the servers in each group and then click on the names to see their machine details). The puppet configuration provides a pretty good reference for software what each server runs however.

Status and problems[edit]

You can check one of the following sites if you want to know if the Wikimedia servers are overloaded, or if you just want to see how they are doing.

If you are seeing errors in real time, visit #wikimedia-techconnect on irc.freenode.net. Check the topic to see if someone is already looking into the problem you are having. If not, please report your problem to the channel. It would be helpful if you could report specific symptoms, including the exact text of any error messages, what you were doing right before the error, and what server(s) are generating the error, if you can tell.

See also[edit]

More hardware info[edit]

Admin logs[edit]

Offsite traffic pages[edit]

Long-term planning[edit]

Out of date information[edit]

Energy consumption[edit]

Useful information about other sites[edit]

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