public int requestCount(Node node) {
            ConcurrentLinkedQueue<ClientRequest> requests = unsent.get(node);
            return requests == null ? 0 : requests.size();
        }
Return whether the caller is still awaiting an IO event.
@return true if so, false otherwise.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/ConsumerNetworkClient.java