What is a useful Azure IoT Hub JSON message structure for consumption in Time Series Insights - json

Question

The title sounds quite comprehensive, but my baseline question is quite simple, I guess.
Context
I Azure, I have an IoT hub, which I am sending messages to. I use a modified version one of the samples from the Azure Iot SDK for python.
Sending works fine. However, instead of a string, I send a JSON structure.
When I watch the events flowing into the IoT hub, using the Cloud shell, it looks like this:
PS /home/marcel> az iot hub monitor-events --hub-name weathertestiothub
This extension 'azure-cli-iot-ext' is deprecated and scheduled for removal. Please remove and add 'azure-iot' instead.
Starting event monitor, use ctrl-c to stop...
{
"event": {
"origin": "raspberrypi-zero-wh",
"payload": "{ \"timestamp\": \"1608643863720\", \"locationDescription\": \"Attic\", \"temperature\": \"21.941\", \"relhumidity\": \"71.602\" }"
}
}
Issue
The data seems fine, except the payload looks strange here. BUT, the payload is literally what I send from the device, using the SDK sample.
Is this the correct way to do it? At the end, I have a very hard time to actually get the data into the Time Series Insights model. So I guess, my structure is to be blamed.
Question
What is a recommended JSON data structure to send to the IoT hub for later use?

Answer 1

You should add the following 2 lines to your message in your python SDK sample:
msg.content_encoding = "utf-8"
msg.content_type = "application/json"
This should resolve your formatting concern.
We've also updated our samples to reflect this: https://github.com/Azure/azure-iot-sdk-python/blob/master/azure-iot-device/samples/sync-samples/send_message.py

Answer 2

I ended up using the tip by #elhorton, but it was not the key change. Nonetheless, the formatting in the Azure Shell Monitor looks now much better:
"event": {
"origin": "raspberrypi-zero-wh",
"payload": {
"temperature": 21.543947753906245,
"humidity": 69.22964477539062,
"locationDescription": "Attic"
}
}
The key was:
include the message source time in ISO format
from datetime import datetime
timestampIso = datetime.now().isoformat()
message.custom_properties["iothub-creation-time-utc"] = timestampIso
Using the locationDescription as the Time Series ID Property See https://learn.microsoft.com/en-us/azure/time-series-insights/how-to-select-tsid (Maybe I could also have taken the iothub-connection-device-id, but I did not test that alone specifically)

Answer 3

I guess using "iothub-connection-device-id" will make "raspberrypi-zero-wh" as the name of the time series instance. I agree with your choice of using "locationDescription" as TSID; so Attic becomes the time series instance name, temperature and humidity will be your variables.