Azure functions decoding error

Question

Azure functions with Python language and Linux hosting are throwing this error when trigger is service bus queue message having IoTHub device connection state message schema.

Result: Failure Exception: ValueError: cannot convert value of field 'SequenceNumber' in trigger metadata into int: invalid literal for int() with base 10: '000000000000000001dummy100000004000000000000000000

Answer 1

Hello @Nayangiri Goswami

The error message suggests that the value of the SequenceNumber field is '000000000000000001dummy100000004000000000000000000', which is not a valid integer value.

To resolve this issue, you can modify the code of your Azure function to handle this specific case. One way to do this is to extract the numeric part of the SequenceNumber field and convert it to an integer. Here's an example of how you can modify your code to handle this case:

import logging
import azure.functions as func
def main(msg: func.ServiceBusMessage): 
  	sequence_number = msg.sequence_number 
	# Extract the numeric part of the sequence number 
	numeric_sequence_number = int(sequence_number.split('dummy')[0]) 
	logging.info(f'Sequence number: {numeric_sequence_number}') 

In this example, we extract the numeric part of the SequenceNumber field by splitting the string at the dummy substring and taking the first part. We then convert this numeric part to an integer using the 'int' function. You can then use this integer value in your function as needed. I hope this helps! Let me know if you have any further questions.

Answer 2

Hi @Nayangiri Goswami Greetings! Thank you for posting this question here.

I could reproduce the same issue you are facing with Python application when trying to process a message triggered from Device Connection Status event generated from IoT Hub through event routing.

I notice that the message body for the message generated through this event consists only a sequenceNumber property in the above-mentioned Base 10 format. The function app is trying to format this sequnceNumber property to an int even before entering the code which is leading to the above error.

Instead of going with routing in IoT Hub, use Events under IoT Hub and create an Event subscription to filter Device Connected and Device Disconnected event types. Choose the end point as Service Bus Queue and point to your queue to send the events. Please find the below image for reference

Once you have this configured, disable any routes you may have under the IoT Hub that sends Device Connection status to the Service Bus Queue end point.

The message delivered to the queue using the event subscription have a different template. Please find the below message body for reference

You can then use the below Function app code to process the message body and extract the sequence number

@app.service_bus_queue_trigger(arg_name="azservicebus", queue_name="lsayanaiot",
                               connection="lsayanaservicebus_SERVICEBUS") 
def lsayana_servicebus_queue_trigger(azservicebus: func.ServiceBusMessage):
    message_body = json.loads(azservicebus.get_body().decode('utf-8'))
    logging.info('Message body is %s', message_body)
    sequence_number = message_body['data']['deviceConnectionStateEventInfo']['sequenceNumber']
    logging.info('Python ServiceBus Queue trigger processed a message: %s',
                sequence_number)

Hope this helps! Please let us know if you have any additional questions or need further assistance.

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