Azure Python function Service Bus outbound attribute

Question

I have a azure python function : It gets triggered by HTTP , responds with HTTP response and puts the message in the Azure Service Bus Queue.

Function.json: for outbound Azure Service bus

{
    "type": "serviceBus",
    "connection": "ServiceBus",
    "name": "outputMessage",
    "queueName": "testqueue",
    "accessRights": "send",
    "direction": "out"
    }

I have function as

def main(req: func.HttpRequest, outputMessage:  func.Out[func.ServiceBusMessage]) -> str:

I get below error: Result: Failure Exception: FunctionLoadError: cannot load the HttpTrg function: type of outputMessage binding in function.json "serviceBus" does not match its Python annotation "ServiceBusMessage"

Question: 1. What should be the python annotation for Azure Service Bus outbound ?

def main( , outputMessage:  func.Out[func.ServiceBusMessage]) 

2. Can I keep -> str for Azure Service Bus ?

   func.Out[func.ServiceBusMessage]) -> str

3. Can i use the set method to send message like :

   outputMessage.set(text)

"To produce multiple outputs, use the set() method provided by the azure.functions.Out interface to assign a value to the binding" -> will this work?

Thanks Sandeep

Answer 1

Using the Azure ServiceBusMessage class as an outbound parameter is not supported:

Attributes are not supported by Python.
Use the Azure Service Bus SDK rather than the built-in output binding.

Azure Service Bus output binding for Azure Functions

ServiceBusMessage can only be used for Trigger binding:

import azure.functions as func
def main(msg: func.ServiceBusMessage):

The queue message is available to the function via a parameter typed as func.ServiceBusMessage. The Service Bus message is passed into the function as either a string or JSON object.

Azure Service Bus trigger for Azure Functions

Answer 2

Another example of being able to do output binding to service bus with python:

// function.json

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "authLevel": "function",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "$return"
    },
    {
      "type": "serviceBus",
      "direction": "out",
      "connection": "AzureWebJobsServiceBusConnectionString",
      "name": "msg",
      "queueName": "outqueue"
    }
  ]
}

.

# __init__.py

import azure.functions as func

def main(req: func.HttpRequest, msg: func.Out[str]) -> func.HttpResponse:

    msg.set(req.get_body())

    return 'OK'

Answer 3

When you say Azure Service Queue you probably mean Azure Storage Queue.

The binding serviceBus is specifically for Service Bus, not Storage Queues.

You need to use queueName.

Here's an example of output binding. Firstly, we have the function.json file:

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "authLevel": "function",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "$return"
    },
  {
      "type": "queue",
      "direction": "out",
      "name": "msg",
      "queueName": "outqueue",
      "connection": "AzureWebJobsStorage"
    }
  ]
}

Now we can use it like so:

import logging

import azure.functions as func


def main(req: func.HttpRequest, msg: func.Out[func.QueueMessage]) -> str:

    name = req.params.get('name')
    if not name:
        try:
            req_body = req.get_json()
        except ValueError:
            pass
        else:
            name = req_body.get('name')

    if name:
        msg.set(name)
        return func.HttpResponse(f"Hello {name}!")
    else:
        return func.HttpResponse(
            "Please pass a name on the query string or in the request body",
            status_code=400
        )

Output Binding with Python to Service Bus

Here's your function.json code:

{
    "name": "outputSbQueue",
    "type": "serviceBus",
    "queueName": "testqueue",
    "connection": "MyServiceBusConnection",
    "direction": "out"
}

Also, the following references may be helpful for you:

Azure Function - Python - ServiceBus Output Binding - Setting Custom Properties https://github.com/yokawasa/azure-functions-python-samples/blob/master/docs/quickstart-v2-python-functions.md https://learn.microsoft.com/en-us/azure/azure-functions/functions-reference-python https://azure.microsoft.com/en-us/blog/taking-a-closer-look-at-python-support-for-azure-functions/

https://unofficialism.info/posts/quick-start-with-azure-function-v2-python-preview/

Sending messages to service bus queue without an explicit binding

from azure.servicebus import QueueClient, Message

# Create the QueueClient
queue_client = QueueClient.from_connection_string(
    "<CONNECTION STRING>", "<QUEUE NAME>")

# Send a test message to the queue
msg = Message(b'Test Message')
queue_client.send(msg)