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JIRA:  

Motivation

In KAFKA-18225, we identified that ClientQuotaCallback#updateClusterMetadata is not supported in KRaft mode, even though it is supported in Zookeeper mode. In Kafka 4.0, we addressed this gap by implementing the missing functionality; however, some limitations still remain:

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public interface ClientQuotaCallback extends Configurable {
	...
     /**
     * This callback is invoked whenever there are changes in the cluster metadata, such as 
     * brokers being added or removed, topics being created or deleted, or partition leadership updates.
     * This is useful if quota computation takes partitions into account.
     * Topics that are being deleted will not be included in `cluster`.
     *
	 * @deprecated since 4.4 and should not be used any longer.
     * @param cluster Cluster metadata including partitions and their leaders if known
     * @return true if quotas have changed and metric configs may need to be updated
     */
	@Deprecated(since = "4.4", forRemoval = true)
    default boolean updateClusterMetadata(Cluster cluster) {
       return false;
	
    }
    ...
}

Documentation

docs/getting-started/upgrade.md

add under Notable changes in 4.4.0

  * The `ClientQuotaCallback#updateClusterMetadata` method is deprecated and will be removed in Kafka 5.0. Custom implementations of `ClientQuotaCallback` no longer need to override this method, as a default no-op implementation is now provided. For further details, please refer to [KIP-1200](https://cwiki.apache.org/confluence/x/axBJFg).

Proposed Changes

Deprecating ClientQuotaCallback#updateClusterMetadata. No alternative method will be introduced, because the method showed no demand during its three-year absence before 4.0, and its reintroduced form contains multiple pitfalls that would require significant effort to fix.

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