If a client connects to MQTT broker with cleanSession=false, the broker creates a durable subscription for the client. If the application/camel-paho is shutdown (e.g. application deployment) the client is being unsubscribed from the topic (doStop() method in PahoConsumer.java). All messages that are sent in the meantime (while the client is offline) are lost for the client (irrespective of QOS level) because of unsubscription.
Expected behaviour: Camel / Paho Route Shutdown should not unsubscribe durable subscribers (QOS > 1) from topics.