Can I create a CI/CD pipeline to deploy Python Function to Azure Function App using Windows self-hosted Azure DevOps agent?

pool:
  vmImage: ubuntu-latest
steps:
- task: UsePythonVersion@0
  displayName: "Setting python version to 3.7 as required by functions"
  inputs:
    versionSpec: '3.7'
    architecture: 'x64'
- bash: |
if [ -f extensions.csproj ]
then
dotnet build extensions.csproj --output ./bin
fi
pip install --target="./.python_packages/lib/site-packages" -r ./requirements.txt
- task: ArchiveFiles@2
  displayName: "Archive files"
  inputs:
    rootFolderOrFile: "$(System.DefaultWorkingDirectory)"
    includeRootFolder: false
    archiveFile: "$(System.DefaultWorkingDirectory)/build$(Build.BuildId).zip"
- task: PublishBuildArtifacts@1
  inputs:
    PathtoPublish: '$(System.DefaultWorkingDirectory)/build$(Build.BuildId).zip'
    artifactName: 'drop'

trigger:
- main
variables:
# Azure service connection established during pipeline creation
  azureSubscription: <Name of your Azure subscription>
  appName: <Name of the function app>
# Agent VM image name
  vmImageName: 'ubuntu-latest'
- task: AzureFunctionApp@1 # Add this at the end of your file
  inputs:
    azureSubscription: <Azure service connection>
    appType: functionAppLinux # default is functionApp
    appName: $(appName)
    package: $(System.ArtifactsDirectory)/**/*.zip
#Uncomment the next lines to deploy to a deployment slot
#Note that deployment slots is not supported for Linux Dynamic SKU
#deployToSlotOrASE: true
#resourceGroupName: '<Resource Group Name>'
#slotName: '<Slot name>'

1. Install it to the following folder on your DevOps machine: $AGENT_TOOLSDIRECTORYPython3.9.9x64; Python version may vary.
2. Install Python for All Users.
3. Manually create an empty x64.complete file. This will indicate that Python “downloading” step is complete during your DevOps operations.

- https://docs.microsoft.com/en-us/azure/devops/pipelines/tasks/tool/use-python-version?view=azure-devops

- bash: |
if [ -f extensions.csproj ]
then
dotnet build extensions.csproj --output ./bin
fi
pip install --target="./.python_packages/lib/site-packages" -r ./requirements.txt

- task: CmdLine@2
  displayName: "Updating Python pip"
  inputs:
    script: 'python.exe -m pip install --upgrade pip'              
    workingDirectory: $(System.DefaultWorkingDirectory)/fapp
- task: CmdLine@2
  displayName: "Installing Python libraries"
    inputs:
    script: 'python.exe -m pip install --target="./.python_packages/lib/site-packages" -r requirements.txt'              
    workingDirectory: $(System.DefaultWorkingDirectory)/fapp

trigger:
  branches:
    include:
    - main
  paths:
    include:
    - fapp/*
    exclude:
    - fapp/README.md
variables:
# Agent VM image name
  vmImageName: ubuntu-latest
stages:
- stage: Build
  displayName: Build stage
  jobs:  
  - job: Build
    displayName: Build
    pool:
      vmImage: $(vmImageName)
    steps:
      displayName: "Updating Python pip"
      inputs:
        script: 'pip install --upgrade pip'              
        workingDirectory: $(System.DefaultWorkingDirectory)/fapp
    - task: CmdLine@2
      displayName: "Installing Python libraries"
      inputs:
        script: 'pip install --target="./.python_packages/lib/site-packages" -r requirements.txt'              
        workingDirectory: $(System.DefaultWorkingDirectory)/fapp
    - task: ArchiveFiles@2
      displayName: "Archive files"
      inputs:
        rootFolderOrFile: "$(System.DefaultWorkingDirectory)/fapp
includeRootFolder: false
archiveFile: "$(System.DefaultWorkingDirectory)/build$(Build.BuildId).zip"
    - task: PublishBuildArtifacts@1
      inputs:
        PathtoPublish: '$(System.DefaultWorkingDirectory)/build$(Build.BuildId).zip'
        artifactName: Functions

Challenges with the non-conventional approach

(A) Python version is important

I didn't include the UsePythonVersion@0 task in my initial YAML code and that proved to be wrong, since I got the old error message again, “Exception: ModuleNotFoundError: No module named 'module_name'”. After further investigation, the Python libs had Linux tag value in their wheel files, however Python version was slightly off. It was deployed as 3.8 version, whre my target Azure Function App was set to the Python 3.9 version.

After setting this YAML task, I had passed on the "No module named " error message:

    - task: UsePythonVersion@0
      displayName: "Setting python version to 3.9 as required by functions"
      inputs:
        versionSpec: '3.9'
        architecture: 'x64'

(B) Import Error: /lib/x86_64-linux-gnu/libm.so.6: version `GLIBC_2.29' not found

Next attempt to build and deploy my code was successful, however the execution of my Python Function App failed with another error message, "ImportError: /lib/x86_64-linux-gnu/libm.so.6: version `GLIBC_2.29' not found".

Thankfully, I wasn't the only one who had experienced the same problem in the past (https://issueexplorer.com/issue/Azure/azure-functions-python-worker/818) and I was able to resolve this issue by replacing the "vmImageName: ubuntu-latest" to "vmImageName: 'ubuntu-18.04'" in my YMAL code, and this helped me a lot!

variables:
# Agent VM image name
  vmImageName: 'ubuntu-18.04'

(C) Build and Release pipeline are separated 

This is a very minor issue to maintain and update both DevOps pipeline (build & release) in two separate places, the rest is easy and very familiar.

Conclusion

As a conclusion to this blog post, I was able to make Linux and Windows, even more, friendlier in my mind by creating this CI/CD pipeline for my Python Function App. Yes, I can deploy the Python Function App to Azure using Windows self-hosted agents, but only if a build is made on a Linux agent too.

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