Writing a Hazelcast / CastMapR MapReduce Task in Java

Hazelcast is a distributed In-Memory-Datagrid written in Java. In addition to the internal features like EntryProcessors and queries you can write MapReduce tasks using the CastMapR projects which adds MapReduce capabilities on top of Hazelcast 3.x. To make it comparable to other MapReduce frameworks we will try to reimplement

CastMapR - The Hazelcast 3 MapReduce Framework

A few days ago while porting our current system to Hazelcast 3 Snapshots I finally decided to start a MapReduce implementation for Hazelcast which I was missing for a long time. Whereas there always was a way to query IMaps in a distributed manner using Predicates I missed a solution