Containerized Python Azure Function cannot start locally

Question

Hi all,

I followed https://learn.microsoft.com/en-us/azure/azure-functions/functions-deploy-container?tabs=acr%2Cbash%2Cazure-cli&pivots=programming-language-python
and I can build docker image on my local machine but starting the container results in failure:

fail: Host.Startup[402]
      The 'function' function is in error: Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions.function'. Microsoft.Azure.WebJobs.Extensions.Storage.Blobs: Storage account connection string 'AzureWebJobsStorage' does not exist. Make sure that it is a defined App Setting.
Hosting environment: Production

This is my Dockerfile:

# To enable ssh & remote debugging on app service change the base image to the one below
# FROM mcr.microsoft.com/azure-functions/python:4-python3.12-appservice
FROM mcr.microsoft.com/azure-functions/python:4-python3.12

ENV AzureWebJobsScriptRoot=/home/site/wwwroot \
    AzureFunctionsJobHost__Logging__Console__IsEnabled=true \
    PYTHON_ISOLATE_WORKER_DEPENDENCIES=1

COPY requirements.txt /
RUN pip install requirements.txt

COPY . /home/site/wwwroot

I put the value of AzureWebJobsStorage to local.settings.json and removed this file from .dockerignore

Is there anything I'm missing? Btw it only doesn't when I run locally

Answer 1

Hi Maria,

Thx for posting your question here at Q&A portal. The problem you're experiencing is that while you've added AzureWebJobsStorage to local.settings.json and removed it from .dockerignore, the Azure Functions runtime in the container isn't picking up these settings. Some issues in your current setup:

local.settings.json isn't automatically loaded in containers, this file is only used by the Functions Core Tools (func host start), not by the container runtime. Missing WORKER_RUNTIME setting - Python functions require this environment variable. Potential pip install issue - your run pip install requirements.txt should be RUN pip install -r requirements.txt ....

FROM mcr.microsoft.com/azure-functions/python:4-python3.12

ENV AzureWebJobsScriptRoot=/home/site/wwwroot \
    AzureFunctionsJobHost__Logging__Console__IsEnabled=true \
    PYTHON_ISOLATE_WORKER_DEPENDENCIES=1 \
    FUNCTIONS_WORKER_RUNTIME=python \
    AzureWebJobsStorage="DefaultEndpointsProtocol=http;AccountName=devstoreaccount1;AccountKey=Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq/K1SZFPTOtr/KBHBeksoGMGw==;BlobEndpoint=http://azurite:10000/devstoreaccount1;QueueEndpoint=http://azurite:10001/devstoreaccount1;TableEndpoint=http://azurite:10002/devstoreaccount1;"

COPY requirements.txt /
RUN pip install -r requirements.txt

COPY . /home/site/wwwroot

I would like to post some recommendations for local development if you like.

Use Azurite for local storage

docker run -d -p 10000:10000 -p 10001:10001 -p 10002:10002 --name azurite mcr.microsoft.com/azure-storage/azurite

Build and run your function with networking

docker build -t mypythonfunction .
docker run -p 8080:80 --link azurite -e AzureWebJobsStorage="UseDevelopmentStorage=true" mypythonfunction

The UseDevelopmentStorage=true setting only works when your function can connect to Azurite on the default ports. For production deployments, you'll need to provide a real storage account connection string. Make sure your requirements.txt file includes azure-functions package. Hope that would help.

rgds, Alex

P.s. If my answer help to you, please Accept my answer