install and setup 3 or more mongod servers in a replicaset setup read preference tags so queries can be controlled to specific servers take one server and disconnect it from all others. e.g. myhost.example.org write a tool in c++ that : uses a ScopedDbConnection to connect mongo cluster perform one or more read-only queries that uses read preference tags to select myhost.example.org exits run tool ./dbtest1 myreplset/myhost.mydomain