[YARN-10573] Enhance placement rule conversion in fs2cs in weight mode and enable it by default

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.0
• Fix Version/s: 3.4.0
• Component/s: capacity scheduler
• Labels: fs2cs
• Target Version/s: 3.4.0
• Hadoop Flags: Reviewed
• Assignee: Peter Bacsko
• Reporter: Peter Bacsko
• Created: 15/Jan/21 12:19
• Updated: 12/Feb/24 01:08
• Resolved: 19/Jan/21 08:43

Description

If we're using weight mode, we have much more freedom when it comes to placement rules.

We need to do three things in this ticket:
#1
In YARN-10525, weight conversion became the default in fs2cs. This also means that we can support nested rules properly and also queues can be created under root. 

Therefore, a lot of warnings and validations inside QueuePlacementConverter are not necessary and only relevant if the user chose percentage-based conversion in the command line.

#2
Remove unnecessary stuff in the RuleHandler which are already supported (plus the test code which affected by this):

• SPECIFIED_NOT_FIRST
• USER_MAX_APPS_DEFAULT
• USER_MAX_RUNNING_APPS

#3
Currently, users have to use "-m" or "--convert-placement-rules" switch to convert the placement rules from FS.
Initially, we converted to the old mapping rule format, which has serious limitations, so we disabled the automatic conversion.
With the new JSON-based format and placement engine, this conversion should happen automatically.