YARN-1197 addresses the functionality of container resource resize. One major use case of this feature is for long running services managed by Slider to dynamically flex up and down resource allocation of individual components (e.g., HBase region server), based on application metrics/alerts obtained through third-party monitoring and policy engine.
One key issue with increasing container resource at any point of time is that the additional resource needed by the application component may not be available on the specific node. In this case, we need to rely on preemption logic to reclaim the required resource back from other (preemptable) applications running on the same node. But this may not be possible today because:
- preemption doesn't consider constraints of pending resource requests, such as hard locality requirements, user limits, etc (being addressed in
YARN-2154and possibly in YARN-3769?)
- there may not be any preemptable container available due to the fact that no queue is over its guaranteed capacity.
What we need, ideally, is a way for YARN to support future capacity planning of long running services. At the minimum, we need to provide a way to let YARN know about the resource usage prediction/pattern of a long running service. And given this knowledge, YARN should be able to preempt resources from other applications to accommodate the resource needs of the long running service.