org.apache.hadoop.mapreduce.task.reduce
Interfaces 
ExceptionReporter
MergeManager
ShuffleScheduler
Classes 
InMemoryReader
InMemoryWriter
MapHost
MapOutput
MapOutput.MapOutputComparator
MergeManagerImpl
Shuffle
ShuffleClientMetrics
ShuffleHeader
ShuffleSchedulerImpl
Enums 
MapHost.State
Exceptions 
Shuffle.ShuffleError