[KAFKA-2530] metrics for old replica fetcher thread need to be deregistered

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 0.8.2.1
• Component/s: core
• Assignee: Unassigned
• Reporter: Jun Rao
• Created: 10/Sep/15 16:45
• Updated: 05/Dec/16 12:37
• Resolved: 05/Dec/16 12:37

Description

Currently, the lag metrics in the replica fetcher has the following format where the leader broker id is included in the clientId tag.

clientId="ReplicaFetcherThread-0-101",partition="0",topic="test",mbean_property_type="FetcherLagMetrics",Value="262"

There are a couple of issues. (1) When the replica changes from a follower to a leader, we will need to set the lag to 0 or deregister the metric. (2) Similarly, when the follower switch to another leader, we should deregister the metric or clear the value. Also, we probably should remove the leader broker id from the clientId tag. That way, the metric name doesn't change when the follower switches leaders.