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Current state: adopted
Discussion thread: here
JIRA:
KAFKA-15980
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STATUS
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
Motivation
The purpose of adding a CurrentControllerId metric is to have an easy way to identify the current controller by looking at the metrics of any Kafka node (broker or controller).
Public Interfaces
CurrentControllerId
Name | Context | Type | Mode | Description |
|---|---|---|---|---|
kafka.server:type=MetadataLoader,name=CurrentControllerId | Broker and Controller | Integer | KRaft and ZK | Outputs the ID of the current controller, or -1 if none is known. |
The CurrentControllerId metric shows the ID of the controller, as seen by the node in question. If the current node doesn't think there is an active controller, the value of thisd metric will be -1.
Compatibility, Deprecation, and Migration Plan
Since this is a new metric, there are no compatibility issues.
Test Plan
The new metric will need unit and integration tests as per usual.
Rejected Alternatives
One rejected alternative is using the existing ActiveControllerCount metric. However, when in KRaft mode, ActiveControllerCount is only exposed on controller nodes, not on broker nodes. That makes it impossible to monitor what the brokers think the current active controller is.