Azure function missing IoT hub trigger messages

Question

I have created an Azure function to route messages from an IoT hub to an Azure SQL DB using the IoTHubTrigger following mostly the instructions in this link Azure Functions - how to set up IoTHubTrigger for my IoTHub messages?.

Each IoT device captures data every 8 minutes. When capturing is done, the device streams the data in 4 different messages. Then the azure function takes over to write these 4 different messages to the database.

When only one device was streaming, I had no issues with the data, which where written in the db and I could also see/monitor events/messages using az iot hub monitor-events.

When a second device started streaming in the same IoT hub, I started missing messages, meaning that from each device only one message is being stored in the db. Also when using iot hub monitor-events only one message appears from each device. I was also expecting that if I disable the 2nd device, then the 1st one will go back to normal. Unfortynately the issue remains the same.

So my question is: how is it possible a 2nd device screwing up the way that the 1st one interacts with the hub?

If that's not the case, then how we are supposed to figure out what causes the problem at this stage?

Thanks :)

Answer 1

Difficult to say without more details. Are you routing messages in IoT Hub somewhere else? I would go back to a clean IoT Hub with one device and create a consumer group on the IoT Hub for the function. Before running the function I would monitor that consumer group (I like to use the Azure IoT Explorer application) to see if data is coming through as expected, then add another device and keep monitoring the same consumer group. If data is coming through then start the function (consuming data from the consumer group). If telemetry was not getting read from the IoT Hub consumer group then you will need to look at your device code for any issues.