[SPARK-29151] Support fraction resources for task resource scheduling

• Type: Story
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.0
• Fix Version/s: 3.0.0
• Component/s: Scheduler, Spark Core
• Assignee: Alessandro Bellina
• Reporter: Thomas Graves
• Created: 18/Sep/19 13:04
• Updated: 17/May/20 17:47
• Resolved: 05/Nov/19 14:58

Description

The current resource scheduling code for GPU/FPGA, etc only supports amounts as integers, so you can only schedule whole resources.  There are cases where you may want to share the resources and schedule multiple tasks to run on the same resources (GPU).  It would be nice to support fractional resources for the task level settings.  Somehow say we want a task to have 1/4 of a GPU for instance.  I think we only want to support fractional when the resources amount is < 1.  Otherwise you run into issues where someone asks for 2 1/8 GPU, which doesn't really make sense to me and makes assigning addresses very complicated.

Need to think about implementation details, for instance using a float can be troublesome here due to floating point math precision issues.

Another thing to consider, depending on implementation is limiting the precision - go down to tenths, hundreths, thousandths, etc.

Issue Links

• relates to: SPARK-24615 SPIP: Accelerator-aware task scheduling for Spark
• relates to: SPARK-27495 SPIP: Support Stage level resource configuration and scheduling
• links to: GitHub Pull Request #26078