Not receiving messages with MqttAsyncClient in Java Paho library

Question

I have a new thread that creates a MqttAsyncClient instance and connects to a remote server. After connecting the client subscribes to a specific topic. If I use the MqttClient instead of the MqttAsyncClient I receive the messages, but if I use the MqttAsyncClient no messages are received. Below is my code, would someone please take a moment to see if I have something missing or incorrect?

public class MqttEventReceiver implements Runnable {

    private static final String CLIENT_ID = UUID.randomUUID().toString();

    private IMqttAsyncClient client = null;

    public MqttEventReceiver(String apiStreamingUri, String 
        connectionAccessToken) {
    }

    private MqttCallback mqttCallback = new MqttCallback() {

        public void messageArrived(String topic, MqttMessage message) throws Exception {
            String incomingMsg = new String(message.getPayload());

            LOG.info("Message: ", new String(payload));
        }

        public void deliveryComplete(IMqttDeliveryToken arg0) {
            // TODO Auto-generated method stub
        }

        public void connectionLost(Throwable arg0) {
            // TODO Auto-generated method stub
        }
    };

    @Override
    public void run() {
        String tmpDir = System.getProperty("java.io.tmpdir");
        MqttDefaultFilePersistence dataStore = new MqttDefaultFilePersistence(tmpDir);

        //make the connect request. this request establishes a permanent connection
        MqttConnectOptions options = new MqttConnectOptions();
        options.setAutomaticReconnect(true);
        options.setCleanSession(true);
        options.setConnectionTimeout(10);
        options.setUserName("authorization");
        options.setPassword(connectionAccessToken.toCharArray());

        Long threadId = successfullyConnected();

        client = new MqttAsyncClient(apiStreamingUri, CLIENT_ID, dataStore);
        client.setCallback(mqttCallback);
        client.connect(options).waitForCompletion();
        client.subscribe("topic", 1).waitForCompletion();
    }
}

Answer 1

Turns out it was the QoS setting causing the message to be delivered slowly. I set the QoS to 0 and the message was delivered promptly.