Containers Reserved Yarn ResourceManager

The management page for yarn RM shows an overview of the cluster, with one indicator called containers Reserved.

Reserved containers, why is reserved, the cluster of resources to use the full, the new app requests the resources will generally enter the pending state, why need to reserve,

Access to the data is that if the app application resources are not easy to allocate, such as the new app is a computationally intensive, a task requires 6 vcores, other tasks need one,

The resources that have just been released will be used by other tasks if they are not reserved, which is unfair.

This is also a feature of yarn fairness Scheduler, for more information on the Fair scheduler, please read:

Fair Scheduler

For best practices in yarn resource management, I also read another article, good, recommended here:

Best practices for YARN Resource Management

Containers Reserved Yarn ResourceManager