All intermediate values associated with a given output key are subsequently grouped by the framework, and passed to the Reducer(s) to determine the final output.

Outputs of the map-tasks go directly to the FileSystem, into the output path set by setOutputPath(Path).

Reporter is also used to update Counters, or just indicate that they are alive.

JobConf is typically used to specify the Mapper, combiner (if any), Partitioner, Reducer, InputFormat, OutputFormat and OutputCommitter implementations.

Task setup takes a while, so it is best if the maps take at least a minute to execute

The child-task inherits the environment of the parent TaskTracker.

To get the values in a streaming job's mapper/reducer use the parameter names with the underscores.

Get the result by passing your Get class instance to the get method of the HTable class. This method returns the Result class object, which holds the requested result.

The child-jvm always has its current working directory added to the java.library.path and LD_LIBRARY_PATH.

You can create a configuration object using the create() method of the HbaseConfiguration class.