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The KIP also proposes adding the ability for users to choose between target cluster's default or source cluster's default when using IncrementalAlterConfigs for syncing topic configurations. For instance, users would be able to configure ConfigPropertyFilter to check if the configuration on the source topic is the default and choose whether or not to replicate it to the target topic. This gives users a bit more control in how they want to replicate their topic configurations. 

Proposed Changes

1) Extend ConfigPropertyFilter  class to have a new method called shouldReplicateSourceDefault which would always return false by default. User would be able to configure this method to return true in order to replicate source cluster's configurations with default values. 2) Add a new configuration setting to MirrorMaker:

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• When explicitly set to "never", MirrorMaker will use the deprecated AlterConfigs API for syncing topic configurations.
• When explicitly set to "required", MirrorMaker will use the IncrementalAlterConfigs API for syncing topic configurations. If it receives an error from an incompatible broker, the MirrorMaker will report this to the user and fail the connector.

2) Extend ConfigPropertyFilter  class to have a new method called shouldReplicateSourceDefault which would return false by default. User would be able to configure this method to return true in order to replicate source cluster's configurations with default values. 

3) From Kafka 4.0, MirrorMaker will use IncrementalAlterConfigs API for syncing topic configuration. 

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