PAHO MQTT 5 throwing exception when using same clientId in routes

Question

When using paho-mqtt5:test more than once with same clientId then it throw exception Client not connected but if i will use different clientId for each to and from then it will work fine

2021-10-05 19:25:28,650 ERROR [org.apa.cam.pro.err.DefaultErrorHandler] (Camel (camel-1) thread #0 - timer://test) Failed delivery for (MessageId: 871E4623819E4FB-000000000000001B on ExchangeId: 871E4623819E4FB-000000000000001B). Exhausted after delivery attempt: 1 caught: Client is not connected (32104)

Message History (complete message history is disabled)
---------------------------------------------------------------------------------------------------------------------------------------
RouteId              ProcessorId          Processor                                                                        Elapsed (ms)
[route1            ] [route1            ] [from[timer://test?period=1000]                                                ] [         0]
    ...
[route1            ] [to1               ] [paho:test                                                                     ] [         0]

Stacktrace
---------------------------------------------------------------------------------------------------------------------------------------
: Client is not connected (32104)
    at org.eclipse.paho.mqttv5.client.internal.ExceptionHelper.createMqttException(ExceptionHelper.java:32)
    at org.eclipse.paho.mqttv5.client.internal.ClientComms.sendNoWait(ClientComms.java:231)
    at org.eclipse.paho.mqttv5.client.MqttAsyncClient.publish(MqttAsyncClient.java:1530)
    at org.eclipse.paho.mqttv5.client.MqttClient.publish(MqttClient.java:564)
    at org.apache.camel.component.paho.mqtt5.PahoMqtt5Producer.process(PahoMqtt5Producer.java:55)
    at org.apache.camel.support.AsyncProcessorConverterHelper$ProcessorToAsyncProcessorBridge.process(AsyncProcessorConverterHelper.java:66)
    at org.apache.camel.processor.SendProcessor.process(SendProcessor.java:172)
    at org.apache.camel.processor.errorhandler.RedeliveryErrorHandler$SimpleTask.run(RedeliveryErrorHandler.java:463)
    at org.apache.camel.impl.engine.DefaultReactiveExecutor$Worker.schedule(DefaultReactiveExecutor.java:179)
    at org.apache.camel.impl.engine.DefaultReactiveExecutor.scheduleMain(DefaultReactiveExecutor.java:64)
    at org.apache.camel.processor.Pipeline.process(Pipeline.java:184)
    at org.apache.camel.impl.engine.CamelInternalProcessor.process(CamelInternalProcessor.java:398)
    at org.apache.camel.component.timer.TimerConsumer.sendTimerExchange(TimerConsumer.java:210)
    at org.apache.camel.component.timer.TimerConsumer$1.run(TimerConsumer.java:76)
    at java.base/java.util.TimerThread.mainLoop(Timer.java:556)
    at java.base/java.util.TimerThread.run(Timer.java:506)

Here is my code which is throwing exception

@ApplicationScoped
class TestRouter : RouteBuilder() {
    override fun configure() {
        val mqtt5Component = PahoMqtt5Component()
        mqtt5Component.configuration = PahoMqtt5Configuration().apply {
            brokerUrl = "tcp://192.168.99.101:1883"
            clientId = "paho123"
            isCleanStart = true
        }
        context.addComponent("paho-mqtt5", mqtt5Component)

        from("timer:test?period=1000").setBody(constant("Testing timer2")).to("paho-mqtt5:test")
  
        from("paho-mqtt5:test").process { e ->
            val body = (e.`in`?.body as? ByteArray)?.let { String(it) }
            println("test body 1 => $body")
        }
               
    }
}

Answer 1

@William, this is expected behavior
The message broker uses the client id to differentiate between clients so it can perform housekeeping for a client connection that is no longer used
In addition, a client may have a "Last Will and Testament" that the broker keeps track of

It is acceptable to append a random number to the end of your current 'clientId' since it is likely no one but you will care about this
If you have access to the individuals login, you could use that as well but you would still want to make each session unique in case they run multiple sessions

Maybe I don't understand what your problem is
Each client must have a unique Id
What are you observing that makes you think that it is creating multiple connections for a single client?
Is there a chance you are opening multiple windows and each is generating a different clientId?

This is a good way to diagnose issues by monitoring what the server is seeing
My paho-mqtt client (Javascript) is connecting as "webclient" and I append a randome number (webclient173) to identify this client
To troubleshoot, I would suggest you close all connections on the client and monitor the log of the MQTT process
When the monitor is in place, open a connection from a client that currently has no connections

This is an example connection to my Mosquitto log file

$ tail -f /var/log/mosquitto/mosquitto.log
1635169943: No will message specified.
1635169943: Sending CONNACK to webclient173 (0, 0)
1635169943: Received SUBSCRIBE from webclient173
1635169943: testtopic (QoS 0)
1635169943: Sending SUBACK to webclient173
1635170003: Received PINGREQ from webclient173
1635170003: Sending PINGRESP to webclient173
1635170003: Received PINGREQ from webclient173
1635170003: Sending PINGRESP to webclient173

What does your log show?