[YARN-9019] Ratio calculation of ResourceCalculator implementations could return NaN

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0, 2.10.3, 3.2.5
• Hadoop Flags: Reviewed
• Assignee: Szilard Nemeth
• Reporter: Szilard Nemeth
• Created: 13/Nov/18 21:11
• Updated: 06/Sep/22 17:25
• Resolved: 05/Dec/18 23:45

Description

Found out that ResourceCalculator.ratio (with implementors DefaultResourceCalculator and DominantResourceCalculator) can produce NaN (Not-A-Number) as a result.

This is because IEEE 754 defines 1.0 / 0.0 as Infinity and -1.0 / 0.0 as -Infinity and 0.0 / 0.0 as NaN, see here: https://stackoverflow.com/a/14138032/1106893 

I think it's very dangerous to rely on NaN can be returned from ratio calculations and this could have side-effects.

When ratio calculates the result and if both the numerator and the denominator is zero, we should use 0 as a result, I think.

Issue Links

• is depended upon by: YARN-8059 Resource type is ignored when FS decide to preempt