@Override
    public String toString() {
        return "ClusterDelta(" +
            "changedBrokers=" + changedBrokers +
            ", changedControllers=" + changedControllers +
            ", nextNodeId=" + nextNodeId +
            ')';
    }
Represents changes to the cluster in the metadata image.
metadata/src/main/java/org/apache/kafka/image/ClusterDelta.java