Contains Mapper, Combiner and Reducer roles to simplify writing Hadoop Streaming jobs

Simplify writing Hadoop Streaming jobs. Combiner follows the same interface as Reducer. Requires a combine() function which will be called for each line of combiner data. Combiners are run on the same machine as the mapper as a pre-reduce reduction step.

Simplify writing Hadoop Streaming Mapper jobs. Write a map() function and let this role handle the Stream interface.

Simplify writing Hadoop Streaming jobs. Write a reduce() function and let this role handle the Stream interface. This Reducer roll provides an iterator over the multiple values for a given key.

Parse input stream for reducer

Collects values for each key together with an iterator interface

Role providing access to values for a given key.

Role to provide emit, counter, and status interaction with Hadoop::Streaming.

Role to require has_next and next