I am using Python v2 programming model to develop azure function for topic output. I want to implement filters so i want to send key value in custom properties in topic but I am unable to set custom properties to message. My code is below.

Question

@app.function_name(name="TopicOut2")
@app.route(route="topic_out2/{sub}")
@app.service_bus_topic_output(arg_name="message", connection="ServiceBusConnectionString", topic_name="testtopicdl")
def test_function(req: func.HttpRequest, message: func.Out[ServiceBusMessage]) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')
    sub = req.route_params.get('sub')
    # logging.info(type(ServiceBusMessage))
    if sub is not None:
        # message_body = {
        #     "msg" : "Hello " + sub,
        #     "sub" : "sub1"
        # }
        message_body = "Hello " + sub
        message_body = send_message(message_body)
        # logging.info(message_body)
        # custom_properties = {
        #     "sub":"sub1"
        # Add more custom properties as needed
    # }
        # message_body_str = json.dumps(message_body)
        message.set(message_body)
    else:    
        logging.info('sub is none')
    return 'ok'

def send_message(toSub: str):
    message_body = "Hello, " + toSub
    logging.info(message_body)
    # Create a ServiceBusMessage instance
    message = ServiceBusMessage(json.dumps({
        "msg":"Hello all"
    }))
    
    # message.application_properties = {

    # }
    logging.info(message)
    return message

Answer 1

One 08 Thanks for posting your question in Microsoft Q&A. Currently, outbound message doesn't support additional attributes such as application properties (or user/custom properties) and feature request #1139 is still open. Please refer to the doc https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-service-bus-output?pivots=programming-language-python&tabs=python-v2%2Cin-process%2Cextensionv5#example for more info on supported parameters.

If you have any feedback on this, please feel free to submit it in GitHub repo or via Azure Functions. Others with similar interests can upvote your idea too. I hope this helps and let me know if you have any questions.

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