Per design in YARN-2938, set up the ATS reader as a service and implement the basic structure as a service. It includes lifecycle management, request serving, and so on.
[Collector implementation] Implement timeline collector functionality to serve ATS readers' requests for live apps
[Data Serving] Handle how to set up and start/stop ATS reader instances
[Data Serving] Clustering of ATS reader instances
[Storage abstraction] Create backing storage read interface for ATS readers