void put(Node node, ClientRequest request) {
            ArrayDeque<ClientRequest> requests = unsent.computeIfAbsent(node, n -> new ArrayDeque<>());
            requests.add(request);
        }
An inter-broker send thread that utilizes a non-blocking network client.
server-common/src/main/java/org/apache/kafka/server/util/InterBrokerSendThread.java