Page History

...

The proposal is to expose the ReplicaPlacer interface. It will move from the org.apache.kafka.controller package in the metadata project to the org.apache.kafka.server.placer package in the clients project. Similarly the existing UsableBroker class will move from org.apache.kafka.metadata package in the metadata project to the org.apache.kafka.server.placer package in the clients project. Sanity checks about the replication factor that are currently performed in StripedReplicaPlacer will be performed in ControlClusterManager as they are common to all ReplicaPlacer implementations.

To address the use cases identified in the motivation section, some knowledge about the current state of the cluster is necessary. Details whether a new broker has just been added or is being decommissioned are not part of the cluster metadata. Therefore such knowledge has to be provided via an external mean to the ReplicaPlacer, for example via the configuration. Apart from configure(), this KIP does not provide a mechanism for defining the behavior of ReplicaPlacer implementation and cluster operators wanting to use this feature will have to build such a mechanism for their specific environments.

The logic assigning replicas to partition differs so much between ZooKeeper and KRaft that I propose making this feature only available in KRaft mode.

...