Issue with Handling Chunked Transfer Encoding in Azure Functions (Python v2)

Question

I am encountering an issue with handling requests that use chunked transfer encoding in my Azure Function (Python v2). When I add the header in Postman and send a POST request, the request fails, and I am unable to properly read the body content.

Steps to Reproduce:

1. I created an HTTP trigger function using Python (v2) in Azure Functions.
2. In Postman, I added the header and sent a POST request with a large payload.
3. The request fails, and when I debug and inspect req.get_body(), it returns an empty byte string (b'').

Expected Behavior: I expect the function to handle the chunked transfer encoding and allow me to process the body of the request as it is streamed.

Current Behavior: The function is unable to retrieve the request body correctly, as req.get_body() returns b'', indicating that no data is being received, even though the client (Postman) is sending data with chunked encoding.

Request: Can you please provide guidance on how to properly handle incoming chunked transfer encoding in Azure Functions with Python v2? Is there a specific configuration or feature I need to enable to support this scenario?

Additional Information:

• I am using the App Service Plan (or specify your plan here).
• I tested using Postman to simulate chunked transfer encoding.
• The issue occurs only when the transfer encoding header is used.

Thank you for your assistance!

Answer 1

Hi @Charles,

When you are sending chunked data to local azure function, it gives you 0 bytes because get_body() will work for chunked data only when deployed to Azure.

Firstly, below is the code which I used:

import azure.functions as func

import logging as rilg

import sys

chop = func.FunctionApp(http_auth_level=func.AuthLevel.ANONYMOUS)

@chop.route(route="http_trigger")

def http_trigger(req: func.HttpRequest) -> func.HttpResponse:

    rilg.info('Hello Rithwik')

    try:

        rith_bdy = req.get_body()  

        rilg.info(f"Received {len(rith_bdy)} bytes")

        body_text = rith_bdy.decode("utf-8")

        return func.HttpResponse(f"Received {len(rith_bdy)} bytes\nData: {body_text}", status_code=200)

    except Exception as cho:

        rilg.error(f"Hello Rithwik, there is an error: {str(cho)}")

        return func.HttpResponse(f"Error: {str(cho)}", status_code=500)

When calling local azure function, I too recieved 0 bytes as this is a known limitation that get_body() will work with chunked data only in Azure.

Deploying to Consumption Plan's Azure Function:

Firstly, created a function app in Consumption plan.

Now deployed the code to the function app created:

After Deploying, It worked even after adding Transfer Encoding : chunked :

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If you have any other questions or still running into more issues, let me know in the "comments" and I would be happy to help you.