MasterSlaveConnection manages a MongoClient directly connected to the master, plus a set of MongoClients directly connected to the slaves. It's little more useful than a set of MongoClient instances managed by the application. Additionally, master-slave setups are themselves obsolete. Replica sets are superior, especially now that the maximum size has been increased (SERVER-15060).

MasterSlaveConnection will be removed in PyMongo 3.0. Deprecate it in 2.8.