Class Summary Class Description BlockManagerMasterMaster-side block manager. BlockManagerMaster.BlockRequestHandlerThe handler of block location requests. BroadcastManagerMasterBroadcast variables saved in the master. PipeManagerMasterMaster-side pipe manager. PlanAppenderAn implementation of plan appender which append two plans regarding to caching. PlanStateManagerMaintains three levels of state machines (PlanState, StageState, and TaskState) of a physical plan. RuntimeMaster(WARNING) Use runtimeMasterThread for all public methods to avoid race conditions.