@Override
    public int hashCode() {
        return Objects.hash(id, rack);
    }
@param id an integer that uniquely identifies this broker
@param rack the rack of the broker, which is used to in rack aware partition assignment for fault tolerance.
            Examples: "RACK1", "us-east-1d"
server-common/src/main/java/org/apache/kafka/admin/BrokerMetadata.java