| CommandClient | A convenient helper to send controller command to ControllerService. | 
| CommandListener | An HTTP server listening to incoming controller commands sent from CommandClient (or any of your favorite REST client
 ) and dispatching the command to the ZooKeeperServerController for execution. | 
| ControlCommand | Set of commands that this controller can execute. | 
| ControllableConnection | Extension of NIOServerCnxn which can inject changes per controller commands. | 
| ControllableConnectionFactory | Extension of NIOServerCnxnFactory which can inject changes per controller commands. | 
| ControllerServerConfig | Config for the ControllerService. | 
| ControllerService | Main class which starts a ZooKeeperServer, a ZooKeeperServerController and the ControllerService. | 
| ZooKeeperServerController | Class which accepts commands to modify ZooKeeperServer state or Connection state at runtime for the purpose of
 single machine integration testing. |