Invalid resource name characters when downloading blob file with Azure Functions-App

Question

I´m trying to download a file from Azure blob storage to to Azure Functions-App temp folder with python.

blobClient = BlobClient.from_connection_string(
    conn_str = os.getenv('CONNECTION_STRING'), 
    container_name = 'data', 
    blob_name = 'data.csv'
)

filepath = os.path.join(tempfile.gettempdir(), 'data.csv')

with open(file = filepath, mode="wb") as file:
    downloadStream = blobClient.download_blob()
    file.write(downloadStream.readall())

On my local development environment it works well without any errors (connection string to cloud blob storgae, not local Azurite), but if i run the Functions-App on cloud environment I get following error:

Result: Failure Exception: HttpResponseError: The specifed resource name contains invalid characters.
[...]
line 366, in __init__ self._response = self._initial_request() File "/home/site/wwwroot/.python_packages/lib/site-packages/azure/storage/blob/_download.py", line 466, in _initial_request process_storage_error(error) File "/home/site/wwwroot/.python_packages/lib/site-packages/azure/storage/blob/_shared/response_handlers.py", line 189, in process_storage_error exec("raise error from None") # pylint: disable=exec-used # nosec File "<string>", line 1, in <module>

Same error appears for upload_blob() in other Functions-App.

I´ve found some similar questions and answers, like no special characters (naming convention) or only blob name not full path but nothing worked for me so far.

It´s the common connection string I´ve received with ''az storage account show-connection-string -g MyResourceGroup -n MyStorageAccount'' — Jens
– Jens, Commented Mar 4, 2023 at 18:05
I don't see an issue with the container name or blob name. Only thing I could think of is invalid connection string. Have you set the environment variable correctly? Can you try to execute other method like exists() on the blob client? — Gaurav Mantri
– Gaurav Mantri, Commented Mar 4, 2023 at 18:13

Venkatesan · Accepted Answer · 2023-03-16 18:51:48Z

I tried to run the function app in my local environment with a wrong container or blob name & I received a similar error code as yours and also check whether the container and blobs are present in the blob storage:-

enter image description here

I deployed my HTTP Trigger function with the code below in the Function app of my Azure Portal:-

_init_.py

import logging
from azure.storage.blob import BlobClient
import tempfile
import os

import azure.functions as func


def main(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')

    blobClient = BlobClient.from_connection_string('<connection-string>;EndpointSuffix=core.windows.net','container-name', 'blob-name')
    filepath = os.path.join(tempfile.gettempdir(), 'secret.txt')
    with open(file = filepath, mode="wb") as file:
      downloadStream = blobClient.download_blob()
      file.write(downloadStream.readall())
      return func.HttpResponse(filepath)

Used the commands below to deploy my Function from the local environment to Azure Portal:-

az login
az account set --subscription "<subscription-name>"

func azure functionapp publish app326

HTTP function got deployed in Azure successfully like below:-

Output:-

enter image description here

Now, When I browse my Azure Function URL, I get the temp file location like the below:-

https://<functionapp>.azurewebsites.net/api/HttpTrigger1

Portal:-

enter image description here

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