[Bug Report] ClassCastException: class com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection cannot be cast to class com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection

[claudiadahl]

Context

• OS and version used: amazoncorretto:25-alpine-jdk (Dockerfile)
• Java runtime used: 25.0.2
• SDK version used: 2.5.1

Description of the issue

We have some DeviceClients - using the IotHubClientProtocol.MQTT - that connects, sends and close their connection afterwards.

In case the IoTHub is not available at the moment that DeviceClients try to reconnect to it causing the following exception:

java.lang.ClassCastException: class com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection cannot be cast to class com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection (com.microsoft.azure.sdk.iot.device.transport.mqtt.MqttIotHubConnection and com.microsoft.azure.sdk.iot.device.transport.amqps.AmqpsIotHubConnection are in unnamed module of loader org.springframework.boot.loader.launch.LaunchedClassLoader @3c27f72)
	at com.microsoft.azure.sdk.iot.device.transport.IotHubTransport.singleDeviceReconnectAttemptAsync(IotHubTransport.java:1464)
	at com.microsoft.azure.sdk.iot.device.transport.IotHubTransport.reconnect(IotHubTransport.java:649)
	at com.microsoft.azure.sdk.iot.device.transport.IotHubReconnectTask.run(IotHubReconnectTask.java:94)
	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:545)
	at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:369)
	at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:310)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1090)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:614)
	at java.base/java.lang.Thread.run(Thread.java:1474)

Since the IoTHub is seldom out of order we do not see that exception very often. But when it is there are a lot of devices that try to reconnect causing a lot of exceptions for a very short time range.