ManagedMqttClient Issue with sending message just after Start.

[pdufrene]

Hello,

Describe the bug

I have the following case:
One server, one client (producer), another client (consumer).
I start the server.
I start the producer and I send immediately a message with retain flag.
I start the consumer and subscribe to the topic.

I am facing a strange behavior where sometimes, the retained message is not received by the consumer.

I am able to work around if I add a Task.Delay(1) between the start of producer and the enqueue of the message.

Which component is your bug related to?

• ManagedClient v4.3.1.873

To Reproduce

Open the attached visual studio solution, execute the unit tests.
There is 2 tests, one where the server is restarted at each loop, another where the server is started only once.
I have Theory, (one with Task.Delay(0) failing, one with Task.Delay(1) success)

Expected behavior

A reproducible behavior without Task.Delay or a way to be sure that initialization is ok.

Code example

See attached solution.

MqttNetTester.zip

[rabejens]

I have a similar problem. I am using the server and the client in an XUnit test, and in my test method, I get very erratic behavior.

With waiting for half a second after starting the client and after subscribing, I receive messages about half the time. Currently, my solution is to ditch the managed client and use the unmanaged one, implementing the reconnection logic myself.

[pdufrene]

The point is that I am facing similar issue in my normal execution environment (Windows 10 Machine) in some rare cases.
This is why I started to isolate the issue using unit tests, but I now realize that XUnit execution is maybe not behaving in same way that normal execution. (Specially on Task management).

I'll try with a regular console application.

[pdufrene]

While testing with external broker (Mosquitto in that case) I don't have the issue, the code works perfectly without Task.Delay.
So I am presuming the issue is in Server part. I saw from the logs that some task are not stopped before a certain amount of time, may be it's related.
@chkr1011 any advice on that ?

[kdurkin77]

Any update on this? I'm having a very similar issue where I need about a half a second delay between starting the managed client and subscribing or I miss messages