[YARN-7921] Transform a PlacementConstraint to a string expression

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.1.0
• Target Version/s: 3.1.0
• Assignee: Weiwei Yang
• Reporter: Weiwei Yang
• Created: 11/Feb/18 09:58
• Updated: 26/Feb/18 20:41
• Resolved: 26/Feb/18 20:24

Description

Purpose:

Let placement constraint viewable on UI or log, e.g print app placement constraint in RM app page. Help user to use constraints and analysis placement issues easier.

Propose:

Like what was added for DS, toString is a reversed process of PlacementConstraintParser that transforms a PlacementConstraint to a string, using same syntax. E.g

AbstractConstraint constraintExpr = targetIn(NODE, allocationTag("hbase-m"));

constraint.toString();

// This prints: IN,NODE,hbase-m