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Improvements in the Hadoop YARN Fair Scheduler

Sandy Ryza goes through the changes in the YARN Fair Scheduler:

A big change in the YARN Fair Scheduler is how it defines a “resource”. In MR1, the basic unit of scheduling was the “slot”, an abstraction of a space for a task on a machine in the cluster. Because YARN expects to schedule jobs with heterogeneous task resource requests, it instead allows containers to request variable amounts of memory and schedules based on those. Cluster resources no longer need to be partitioned into map and reduce slots, meaning that a large job can use all the resources in the cluster in its map phase and then do so again in its reduce phase. This allows for better utilization of the cluster, better treatment of tasks with high resource requests, and more portability of jobs between clusters — a developer no longer needs to worry about a slot meaning different things on different clusters; rather, they can request concrete resources to satisfy their jobs’ needs. Additionally, work is being done (YARN-326) that will allow the Fair Scheduler to schedule based on CPU requirements and availability as well.

Basically the scheduler in Hadoop goes from a minimum viable product to a resource aware scheduler. But as far as I know, schedulers in commercial MPP systems are even smarter and more configurable, so there’s still room for improvements.

Original title and link: Improvements in the Hadoop YARN Fair Scheduler (NoSQL database©myNoSQL)