The multi-datacenter work requires cirrussearch to be able to fail over from querying the local cluster to querying a cluster in another datacenter over the WAN. It additionally requires being able to write to both clusters from a single instance of php in any cluster.
Currently Elastica\Connection is a singleton, but mmulie made it possible to use as a normal object as well. Cirrussearch should be refactor to create and pass arround connection objects, rather than reuse a singleton all over the place.
Related: T105707