Functions

This guide shows you how to work with Azure Functions using Python and Azure Functions Core Tools. This lab demonstrates how to develop, run, debug, test, and validate an HTTP-triggered function locally.

Prerequisites

• Docker installed and running.
• Dev Containers extension installed (optional).

How to execute

1. Setup Environment:

   Dev Container (recommended)

   Open VS Code in the project folder and execute this command in the Command Palette:

   > Dev Containers: Reopen in Container

   Manually
   1. Run the setup script to install tools and dependencies.

      scripts/setup.sh

   2. Start Infrastructure: Launch the required containers.

      docker compose up -d

2. Start Function Host:

   Terminal

   func start

   Run and Debug
   • Open: Open the Run and Debug tab in VS Code.
   • Run: Select Attach to Python Functions and press F5. The emulator starts and the debugger attaches automatically.
   Azure Functions Extension
   • Open: Open the Azure sidebar and navigate to Workspace → Local Project → Functions.
   • Run: Click the Start debugging button to start the function app.

3. Run the Example:

   Python

   python main.py

   cURL
   • Admin (success):

     curl "http://localhost:7071/api/get_secret?username=admin"

   • Other user (forbidden):

     curl "http://localhost:7071/api/get_secret?username=guest"

   REST Client
   • Install: REST Client from de VS Code Marketplace.
   • Open: Open http/get_secret.http in VS Code.
   • Run: Click Send Request above any request block.

How to debug

1. function_app.py:

   • Open: Open function_app.py.
   • Breakpoints: Set breakpoints inside get_secret.
   • Run: From the Run and Debug tab, select Attach to Python Functions and press F5.

2. main.py:

   • Open: Open main.py.
   • Breakpoints: Set breakpoints in the main function.
   • Run: Press F5 to start debugging.

3. Tests:

   • Open: Open a test file (e.g., tests/test_functions.py).
   • Breakpoints: Set breakpoints in the test code.
   • Run: Use the VS Code Testing tab and click the Debug Test icon next to the test you want to debug.

How to test

• Individually: Run tests individually from the VS Code Testing tab.
• All tests: Run the automated script:

  scripts/run_tests.sh

Validate results

Terminal

• Run: Execute the main script and review its output:

  python main.py

• Verify: The user defined in ADMIN_USERNAME (.env) should receive a 200 response with the secret value. Any other user should receive 403.

Logs

• Open: Review the terminal where func start is running.
• Verify: Each request logs a line like Python HTTP trigger function processed a request.

Clean Up

docker compose down -v

Next steps

• Build on this MVE with the Storage Writer project.
• Build on this MVE with the SQL Writer project.
• See the AWS equivalent Lab.