Client isn't being notified if message is not delivered

[EdwardSkrobala]

Summary

Our team faced up with issue on our production environment - after RabbitMQ maintance all queues were deleted and our client is still publishing messages without any error.
We've prepared a short Pub/Sub demo reproducing it (https://github.com/EdwardSkrobala/MqttIssue).

Publisher & Subscriber connect to broker via websockets, publisher sends message every 5 sec with Qos-1 level set.
We need publisher to be acknowledged if it publishes message that is not delivered to subscriber.

Environment:

• .NET Core 3.0
• RabbitMQ 3.7
• Plugin: Mqtt
• Client Lib: MQTTnet 3.0.8 (https://github.com/chkr1011/MQTTnet)

Steps to reproduce:

• Run docker-compose -f docker-compose-brokers.yml up from root folder
• Run dotnet run from project folder (src/Test/)
• Trigger management UI - http://localhost:15672/#/queues (username="test", pass="test")
• Delete Queue mqtt-subscription-subscriberqos1 to simulate maintance on server.

Code lines showing issue

Message configuration
var message = new MqttApplicationMessageBuilder() .WithTopic("MyTopic") .WithPayload($"Hello World [{DateTime.Now.ToLongTimeString()}]") .WithQualityOfServiceLevel(MQTTnet.Protocol.MqttQualityOfServiceLevel.AtLeastOnce) .WithRetainFlag(false) .Build()
PublishAsync returns MqttClientPublishResult containing MqttClientPublishReasonCode (https://github.com/chkr1011/MQTTnet/blob/master/Source/MQTTnet/Client/Publishing/MqttClientPublishResult.cs)
var publishResult = await publisherClient.PublishAsync(message)

Expected result:
Exception or MqttClientPublishResult.ReasonCode = MqttClientPublishReasonCode.NoMatchingSubscribers

Actual result:
MqttClientPublishResult.ReasonCode = Success

Thanks in advance for the assistance