void sendInternalMetadataRequest(MetadataRequest.Builder builder, String nodeConnectionId, long now) {
        ClientRequest clientRequest = newClientRequest(nodeConnectionId, builder, now, true);
        doSend(clientRequest, true, now);
    }
Queue up the given request for sending. Requests can only be sent out to ready nodes.
@param request The request
@param now The current timestamp
clients/src/main/java/org/apache/kafka/clients/NetworkClient.java