[KAFKA-10189] Reset metric EventQueueTimeMs

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.7.0
• Component/s: controller, core, metrics
• Assignee: Jeff Kim
• Reporter: Jeff Kim
• Reviewer: José Armando García Sancio
• Created: 19/Jun/20 22:38
• Updated: 21/Jul/20 00:56
• Resolved: 21/Jul/20 00:56

Description

The metric EventQueueTimeMs does not reset and therefore misrepresents the controller event queue time in these two scenarios:
1. upon losing leader election - `EventQueueTimeMs` portrays the last event queue time of the previous controller and not the current controller
2. no controller events are added to the queue - `EventQueueTimeMs` portrays the most recent event queue time, not the current queue time (which is 0)

For both cases, we should reset the controller event queue time to 0.

Implementation:

Instead of using `LinkedBlockingQueue.take()` here, we can use `LinkedBlockingQueue.poll(long timeout, TimeUnit unit)` and reset `EventQueueTimeMs` if the queue is empty.

Issue Links

• links to: GitHub Pull Request #8935