[YARN-6769] Make schedulables without demand less needy in FairSharePolicy#compare

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.7.2
• Fix Version/s: 2.9.0, 3.0.0-beta1
• Component/s: fairscheduler
• Target Version/s: 2.8.1
• Assignee: YunFan Zhou
• Reporter: YunFan Zhou
• Created: 07/Jul/17 02:09
• Updated: 22/Jul/17 15:44
• Resolved: 14/Jul/17 06:16

Description

When use fairsheduler as RM scheduler, before assign container we will sort all queues or applications.
We will use FairSharePolicy#compare as the comparator， but the comparator is not so perfect.
It have a problem as blow:
1. when a queue use resource over minShare(minResources), it will put behind the queue whose demand is zeor.
so it will greater opportunity to get the resource although it do not want. It will waste schedule time when assign container
to queue or application.

I have fix it, and I will upload the patch to the jira.