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From Wikitech

The linked pages contain technical documentation on how search works on Wikipedia and its sister projects (Wikimedia Commons, Wikidata, etc). This software and infrastructure are owned and supported by the Wikimedia Foundation’s Search Platform team.

In case of emergency

Here is the (sorted) emergency contact list for Search issues on the WMF production clusters:

Name IRC nick
David Causse dcausse
Erik Bernhardson ebernhardson
Brian King inflatador
Ryan Kemper ryankemper
Guillaume Lederrey gehel

You can get contact information from officewiki.


The WMF’s production system has four components: Elastica, CirrusSearch, Cirrus Streaming Updater, and Elasticsearch.


Elastica is a MediaWiki extension that provides the library to interface with Elasticsearch. It wraps the Elastica library. It has no configuration.


CirrusSearch is a MediaWiki extension that provides search support backed by Elasticsearch. For more details about how the CirrusSearch Mediawiki plugin is deployed in WMFs production environment, see this page.

Cirrus Streaming Updater

The Cirrus Streaming Updater updates the Elasticsearch indexes for each and every mediawiki edit. In other words, when someone edits a Wikipedia page, this is the process that finds the edit and adds it to the Elasticsearch index, making it possible for others to find it via a search from a Wikipedia page.


Elasticsearch is the application that stores our search data. It can be queried via its rest API. For more details on how Elasticsearch is deployed in WMF’s production environment, see this page.