public DocumentProtocolRoutingPolicy createPolicy(String param) {
            if (config != null) {
                if (config.cluster(param) == null)
                    return new ErrorPolicy("No message type config for cluster '" + param + "'");

                return new MessageTypePolicy(config.cluster(param));
            }
            return new MessageTypePolicy(param == null || param.isEmpty() ? configId : param);
        }
@author Simon Thoresen Hult
@author jonmv
documentapi/src/main/java/com/yahoo/documentapi/messagebus/protocol/RoutingPolicyFactories.java