Retrieve sensor data from Azure EventHub Message with Azure Function (Python)

Question

I'm trying to send sensor data from a device to Azure IoT Hub and process it inside Azure Function. I managed to trigger the function when Azure IoT Hub receives data using EventHubTrigger.

However, I cannot find any way to retrieve sensor data.

The following data is sent from the device:

{"temperature": 27.5, "humidity": 63.0}

And the bellow is what I get from EventHubEvent body

{'properties': {}, 'systemProperties': {'iothub-connection-device-id': 'raspberrypi', 'iothub-connection-auth-method': '{"scope":"device","type":"sas","issuer":"iothub","acceptingIpFilterRule":null}', 'iothub-connection-auth-generation-id': '637374141338740275', 'iothub-enqueuedtime': '2020-10-04T16:21:15.0190000Z', 'iothub-message-source': 'Telemetry'}, 'body': 'eyJ0ZW1wZXJhdHVyZSI6IDI3LjUsICJodW1pZGl0eSI6IDYzLjB9'}

Source code for the sender and function app is as follows:

Sender/device (related part only)

# Define the JSON message to send to IoT Hub.
MSG_TXT = '{{"temperature": {temperature}, "humidity": {humidity}}}'

client = IoTHubDeviceClient.create_from_connection_string(CONNECTION_STRING)

msg_txt_formatted = MSG_TXT.format(temperature=sensor_data["temperature"]["value"], humidity=sensor_data["humidity"]["value"])
message = Message(msg_txt_formatted)
client.send_message(message)

Function app （__init__.py)

from typing import List
import logging
import json

import azure.functions as func

def main(event: List[func.EventHubEvent]):
    body = event.get_body()
    logging.info(body)
    my_json = body.decode('utf8').replace("'", '"')
    event_data_json = json.loads(my_json)
    logging.info(event_data_json[0]["data"])

Is there any additional setting necessary to route IoTHub telemetry data? Any help would be appreciated.

Have you set up message routing for Device telemetry messages in IoT hub? — iAviator
thanks a lot! I didn't notice that I need to add the custom endpoints.. — Shoko
thanks for clarification. I have added the answer based on your inputs.You can accept it. — iAviator

iAviator iAviator · Accepted Answer · 2020-10-05T13:01:01

You need to add message routing from IoT hub blade. If using Built in end point event hub, route the DeviceTelemetry messages to events endpoint else route to the custom endpoint i.e. in this case it is your event hub created in event hub namespace.

Retrieve sensor data from Azure EventHub Message with Azure Function (Python)

1 Answers