public static enum ConsumerPartitionAssignor.RebalanceProtocol
extends Enum<ConsumerPartitionAssignor.RebalanceProtocol>

The rebalance protocol defines partition assignment and revocation semantics. The purpose is to establish a consistent set of rules that all consumers in a group follow in order to transfer ownership of a partition. ConsumerPartitionAssignor implementors can claim supporting one or more rebalance protocols via the ConsumerPartitionAssignor.supportedProtocols(), and it is their responsibility to respect the rules of those protocols in their ConsumerPartitionAssignor.assign(Cluster, GroupSubscription) implementations. Failures to follow the rules of the supported protocols would lead to runtime error or undefined behavior. The EAGER rebalance protocol requires a consumer to always revoke all its owned partitions before participating in a rebalance event. It therefore allows a complete reshuffling of the assignment. COOPERATIVE rebalance protocol allows a consumer to retain its currently owned partitions before participating in a rebalance event. The assignor should not reassign any owned partitions immediately, but instead may indicate consumers the need for partition revocation so that the revoked partitions can be reassigned to other consumers in the next rebalance event. This is designed for sticky assignment logic which attempts to minimize partition reassignment with cooperative adjustments.