[IMPALA-8858] Add metrics to improve observability of idle executor groups

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Impala 3.4.0
• Epic Color: ghx-label-2
• Assignee: Bikramjeet Vig
• Reporter: Andrew Sherman
• Created: 13/Aug/19 00:36
• Updated: 20/Sep/19 21:08
• Resolved: 20/Sep/19 21:08

Description

The metrics provided in IMPALA-8806 are useful but there is not a way to see how many executor groups are idle.
Please add a metric which measures the number of executor groups that are both healthy and idle.
It is OK to for this to be 0 for a short time for example when an executor group is created.
This should be part of the new "cluster-membership" metric group.