Get target route parameters when using proxies

Investigative information

Please provide the following:

• Function App version: 2.0.12285
• Python worker version: 1.0.0b3
• Function name: test-list

Repro steps

1. Create sample function based on source code below
2. Hit API /api/list_proxy/group_1/product_a?validate=true
3. It should be routed to /api/list/

Expected behavior

I expected to have route parameter from the target function and some additional information from source proxy in another property:

{
  "route_params": {
    "group": "group_1",
    "product": "product_a"
  },
  "params": {
    "validate": "true"
  }
}

Actual behavior

Instead I have the route params from the original proxy:

{
  "method": "POST",
  "url": "http://localhost:7071/api/list/group_1/product_a?validate=true",
  "headers": {
    "connection": "keep-alive"
  },
  "route_params": {
    "restOfPath": "group_1/product_a"
  },
  "params": {
    "validate": "true"
  },
  "get_body": ""
}

Known workarounds

We will add logic to our Function App to reconstruct the route params by using the URL and route from function.json.

Related information

Provide any related information

• Sample source files

Source

## function.json
{
  "scriptFile": "__init_py",
  "bindings": [
    {
      "authLevel": "anonymous",
      "type": "httpTrigger",
      "direction": "in",
      "name": "request",
      "methods": [
        "post"
      ],
      "route": "list/{group}/{product}"
    },
    {
      "type": "http",
      "direction": "out",
      "name": "$return"
    }
  ]
}

## proxies.json
{
  "proxies": {
    "internal-routing": {
      "matchCondition": {
        "route": "/api/list_proxy/{*restOfPath}"
       },
       "backendUri": "https://localhost/api/list/{restOfPath}"
      },
  }
}

## __init_py
def main(request: azure.functions.HttpRequest) -> azure.functions.HttpResponse:

    route_params = {}
    if hasattr(request, 'route_params'):
        route_params = dict(request.route_params)
    params = {}
    if hasattr(request, 'params'):
        params = dict(request.params)
    headers = dict(request.headers)
    return json.dumps({
        'method': request.method,
        'url': request.url,
        'headers': headers,
        'route_params': route_params,
        'params': params,
        'get_body': request.get_body().decode(),
    })

[alexkarcher-msft]

Cool! I was able to repo this issue on my own with a JS function, and setting the app setting AZURE_FUNCTION_PROXY_DISABLE_LOCAL_CALL to true restored the correct behavior.

We’re going to take a look at the root cause for this, but that app setting should mitigate the issue for the time being 🙂

[jeffhollan]

Thanks @alexkarcher-msft and @eduardomourar for investigation. Closing this one and will track work item here: https://github.com/Azure/azure-functions-host/issues/3593