Manual:$wgLBFactoryConf

Details
To set up a multi-master wiki farm, set the class here to something that can return a LoadBalancer with an appropriate master on a call to getMainLB. The class identified here is responsible for reading $wgDBservers, $wgDBserver, etc., so overriding it may cause those globals to be ignored.

The LBFactory_Multi class is provided for this purpose, the configuration for this class is provided below:

If you use this class, all previous settings like $wgDBservers, $wgExternalServers, ... will be ignored.


 * sectionsByDB
 * A map of database names to section names


 * sectionLoads
 * A 2-d map. For each section, gives a map of server names to load ratios. For example:


 * serverTemplate
 * A server info associative array as documented for $wgDBservers. The host, hostName and load entries will be overridden.


 * groupLoadsBySection
 * A 3-d map giving server load ratios for each section and group. For example:


 * groupLoadsByDB
 * A 3-d map giving server load ratios by DB name.


 * hostsByName
 * A map of hostname to IP address.


 * externalLoads
 * A map of external storage cluster name to server load map


 * externalTemplate
 * A server info structure used for external storage servers


 * templateOverridesByServer
 * A 2-d map overriding mainTemplate or externalTemplate on a server-by-server basis.


 * templateOverridesByCluster
 * A 2-d map overriding externalTemplate by cluster


 * masterTemplateOverrides
 * An override array for mainTemplate and externalTemplate for all master servers.

Wikimedia configuration
To see how Wikimedia uses  to configure its wikis see:
 * db-eqiad.php