When the MQTT Endpoint is started the MQTT connection is immediately established, causing an immediate influx of persisted messages (put on the topic when the client was not available).
Issue is that at this point, most likely no consumers are available yet to process these messages.
Receiving a PUBLISH message
Publish message are received without any consumers. Result : msg with QoS > 0 that were put on the topic while the client was not connected are never processed.
Daemon Thread [hawtdispatch-DEFAULT-3] (Suspended (breakpoint at line 815 in CallbackConnection))
CallbackConnection.toReceiver(PUBLISH) line: 815
CallbackConnection.processFrame(MQTTFrame) line: 732
CallbackConnection.access$1500(CallbackConnection, MQTTFrame) line: 51
CallbackConnection$6.onTransportCommand(Object) line: 392
TcpTransport.drainInbound() line: 709
TcpTransport$6.run() line: 588
NioDispatchSource$3.run() line: 209
SerialDispatchQueue.run() line: 100
SimpleThread.run() line: 77
No consumers registered yet
Only when this finishes will Camel be able to process the messages.
Daemon Thread [localhost-startStop-1] (Suspended (breakpoint at line 164 in MQTTEndpoint))
owns: SpringCamelContext (id=92)
owns: Object (id=143)
owns: StandardContext (id=144)
MQTTEndpoint.addConsumer(MQTTConsumer) line: 164
MQTTConsumer.doStart() line: 35
MQTTConsumer(ServiceSupport).start() line: 61
SpringCamelContext(DefaultCamelContext).startService(Service) line: 2158
SpringCamelContext(DefaultCamelContext).doStartOrResumeRouteConsumers(Map<Integer,DefaultRouteStartupOrder>, boolean, boolean) line: 2452
SpringCamelContext(DefaultCamelContext).doStartRouteConsumers(Map<Integer,DefaultRouteStartupOrder>, boolean) line: 2388
SpringCamelContext(DefaultCamelContext).safelyStartRouteServices(boolean, boolean, boolean, boolean, Collection<RouteService>) line: 2318
SpringCamelContext(DefaultCamelContext).doStartOrResumeRoutes(Map<String,RouteService>, boolean, boolean, boolean, boolean) line: 2091
SpringCamelContext(DefaultCamelContext).doStartCamel() line: 1951
SpringCamelContext(DefaultCamelContext).doStart() line: 1777
These messages will never be picked up.
Perhaps it's more the responsibility of the consumer / producer to start a connection when they get attached to the endpoint ?