MR3 is a new execution engine for Hadoop. Similar in spirit to (and inspired by) Tez, it can be thought of as an enhancement of Tez with simpler design, better performance, and more features. MR3 is ready for production use as it supports all major features from Tez such as Kerberos-based security, authentication and authorization, fault-tolerance, and recovery.
MR3 serves as a framework for running jobs in Hadoop and can work with different runtime environments. Currently its supports runtime environments of Tez 0.7.0, 0.8.4, and 0.9.1. MR3 also has its own runtime, called ASM, which is under development as a research project.
MR3 is implemented in Scala. Currently it is distributed in binary form as part of Hive-MR3, an extension of Hive that runs on top of MR3.