[BUG] Result: Failure Exception: ModuleNotFoundError: No module named 'azure.storage'.

I’ve got an Azure Function app with two Azure Functions which use external packages (e.g. azure-storage-blob). In VSCode locally (even if it’s a Windows box) this works fine. I have a CI/CD pipeline which deploys the function app to Azure using the recommended approach by Microsoft described here. The deployment works fine as well and the Azure Functions run successfully until I use external packages. When I do so, the following error occurs:

Result: Failure Exception: ModuleNotFoundError: No module named 'azure.storage'. 
Troubleshooting Guide: https://aka.ms/functions-modulenotfound Stack: File "/azure-functions-host/workers/python/3.6/LINUX/X64/azure_functions_worker/dispatcher.py", line 275, 
in _handle__function_load_request func_request.metadata.entry_point) File "/azure-functions-host/workers/python/3.6/LINUX/X64/azure_functions_worker/utils/wrappers.py", line 34, 
in call raise extend_exception_message(e, message) File "/azure-functions-host/workers/python/3.6/LINUX/X64/azure_functions_worker/utils/wrappers.py", line 32, 
in call return func(*args, **kwargs) File "/azure-functions-host/workers/python/3.6/LINUX/X64/azure_functions_worker/loader.py", line 76, 
in load_function mod = importlib.import_module(fullmodname) File "/usr/local/lib/python3.6/importlib/__init__.py", line 126, 
in import_module return _bootstrap._gcd_import(name[level:], package, level) File "/home/site/wwwroot/GenerateReport/__init__.py", line 5, 
in <module> import azure.storage.blob as azureBlob

I investigated all the things described here all the root causes do not seem to match:

• Package exists in the zip file in .python_packages/lib/site-packages/azure/storage/blob (as it does locally)
• Tag section in the WHEEL file contains Tag: py3-none-any which indicates it should run on linux
• Classifier section in the METADATA file contains
  • Classifier: Programming Language :: Python :: 3.5
  • Classifier: Programming Language :: Python :: 3.6
  • Classifier: Programming Language :: Python :: 3.7
  • Classifier: Programming Language :: Python :: 3.8
  • Classifier: Programming Language :: Python :: 3.9 so should be ok as well
• There are no conflicts with other packages described here and I do not have the deprecated azure-storage package referenced in requirements.txt
• The package supports linux I think: https://pypi.org/project/azure-storage-blob/12.7.1/ At least it’s not mentioned that it isn’t. But here I’m not sure.

The service plan of the Azure Function App is a Consumption plan (Y1).

What I also tried:

• Use Azure Function Core Tools to deploy instead: func azure functionapp publish <app-name> --build-native-deps This leaded into the same error.
• I tried to use the following versions of Python 3.6, 3.7, 3.8, 3.8 both for the pip install --target="./.python_packages/lib/site-packages" -r ./requirements.txt command and the LinuxFxVersion of the Azure Function App. There I used the notation Python|3.x
• I removed the dependency to the package azure-storage-blob but left a dependency to another external package (fpdf2). The result was the following error: Result: Failure Exception: ModuleNotFoundError: No module named 'fpdf2'.
• I locally renamed folder .venv\Lib\site-packages\azure to .venv\Lib\site-packages\azure_ which lead to the same error: Exception: ModuleNotFoundError: No module named 'azure.storage'.

So to me it looks like the azure function totally ignores the folder .python_packages/lib/site-packages/ somehow.

Perhaps this is related to the following issues which did not help in my case: https://github.com/Azure/azure-functions-python-worker/issues/477 https://github.com/Azure/azure-functions-python-worker/issues/800

Investigative information

Please provide the following:

• Timestamp: 2021-02-17 12:33:00.049
• Function App name: bc-func-batch-analytics-dev
• Function name(s) (as appropriate): GenerateReport
• Core Tools version: 3.0.3233
• Azure region: West Europe

Expected behavior

Provide a description of the expected behavior.

After deployment the Azure Function App should run the same way as it does locally.

Actual behavior

Provide a description of the actual behavior observed.

It runs locally but it doesn’t on Azure because of the following error mentioned above: Result: Failure Exception: ModuleNotFoundError: No module named 'azure.storage'.

Contents of the requirements.txt file:

Provide the requirements.txt file to help us find out module related issues.

azure-functions
azure-storage-blob
fpdf2

[oliverchristen]

I found the reason why it was not working. I was just missing to set environment variable FUNCTIONS_WORKER_RUNTIME to python.

It’s just weird to me that it works fine without external packages even without this environment variable.

Hope this helps someone.

[caffinit]

@abhiraj1289 Thank you for the reply! Your comments helped me get past this exception.