Exhibit Deadlock in Paho Java Client

Deadlock.java

package org.springframework.integration.mqtt;

import org.eclipse.paho.client.mqttv3.IMqttDeliveryToken;
import org.eclipse.paho.client.mqttv3.MqttCallback;
import org.eclipse.paho.client.mqttv3.MqttClient;
import org.eclipse.paho.client.mqttv3.MqttMessage;

/**
 * @author Gary Russell
 *
 */
public class Deadlock implements MqttCallback {

	private final MqttClient mqttClient1;

	private final MqttClient mqttClient2;

	public static void main(String[] args) throws Exception {
		new Deadlock().test();
	}

	private Deadlock() throws Exception {
		mqttClient1 = new MqttClient("tcp://iot.eclipse.org:1883", "foo");
		mqttClient1.setCallback(this);
		mqttClient1.connect();
		mqttClient2 = new MqttClient("tcp://iot.eclipse.org:1883", "bar");
		mqttClient2.setCallback(this);
		mqttClient2.connect();
		mqttClient2.subscribe("bar");
	}

	private void test() throws Exception {
		for (int i = 0; i < 16; i++) {
			System.out.println("sending");
			mqttClient1.publish("bar", new MqttMessage("foo".getBytes()));
		}
	}

	@Override
	public void connectionLost(Throwable cause) {
	}

	@Override
	public void messageArrived(String topic, MqttMessage message) throws Exception {
		System.out.println(new String(message.getPayload()));
		Thread.sleep(5000);
		throw new RuntimeException("deadlock");
	}

	@Override
	public void deliveryComplete(IMqttDeliveryToken token) {
	}

}

Hi garyrussell ,
I am facing the same issue as referenced on
http://stackoverflow.com/questions/25620196/spring-integration-mqtt-subscriber-paho-stops-processing-messages

On my application i am pushing continious huge load I found that, sometimes application is dropping connection with IMA (mqtt) and this was happened three times in a span of 1 Lac record.
But it regains the connectivity and started consuming messages received there after.
There is some other issue which I faced during this testing.

When there is continuous load on application , at some point application stops receiving messages and we can see one message flashed on screen i.e.

May 04, 2015 2:45:29 PM org.eclipse.paho.client.mqttv3.internal.ClientState checkForActivity
SEVERE: HUGHJACK:gvjIpONtSpP: Timed out as no activity, keepAlive=60,000 lastOutboundActivity=1,430,730,869,017 lastInboundActivity=1,430,730,929,151

After this we can see that there are no messages received on application even if continuous load is pushed through utility.
This behavior I found it three times.

• At around 40K.
• At around 90K.
• At around 145K.

There is no consistent point or figures where application actually stops receiving messages.
So is this problem solved in the next releases, i am using 4.0.4 version. Please let me know .