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README_AZURE_STARTUP.md

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Azure App Service - Startup Configuration

Problem

Azure App Service is trying to use eventlet worker class but the module is not installed, causing:

ModuleNotFoundError: No module named 'eventlet'

Solution

Option 1: Use Startup Script (Recommended)

  1. Ensure requirements.txt is in the correct location:

    • The requirements.txt should be in /home/site/wwwroot/backend/ or /home/site/wwwroot/
    • Azure App Service automatically installs dependencies from requirements.txt during build

  2. Configure Azure App Service Startup Command:

    • Go to Azure Portal → Your App Service → Configuration → General settings
    • Set Startup Command to: 
      cd /home/site/wwwroot/backend && bash startup.sh
    • Or if your app is in the root: 
      bash startup.sh

  3. Alternative: Use Python directly with requirements installation:

    pip install -r requirements.txt && gunicorn --bind=0.0.0.0:8000 --worker-class eventlet --workers=1 app:app

Option 2: Use Sync Worker (No eventlet needed)

If you don't need WebSocket support or can use a different approach:

  1. Change startup command to:

    gunicorn --bind=0.0.0.0:8000 --worker-class sync --workers=4 --timeout=120 app:app

  2. Note: This won't support WebSocket connections. For WebSocket support, you need eventlet or gevent.

Option 3: Use Gevent Worker (Alternative to eventlet)

  1. Add to requirements.txt:

    gevent==23.9.1
gevent-websocket==0.10.1

  2. Change startup command to:

    gunicorn --bind=0.0.0.0:8000 --worker-class gevent --workers=1 --timeout=120 app:app

Option 4: Ensure Requirements.txt is Installed

The most common issue is that Azure isn't finding or installing requirements.txt.

  1. Check file location:

    • Requirements.txt should be in the deployment root or backend directory
    • Azure looks for it in /home/site/wwwroot/requirements.txt or /home/site/wwwroot/backend/requirements.txt

  2. Enable Oryx build:

    • Go to Azure Portal → Configuration → General settings
    • Ensure "Always On" is enabled
    • Check "SCM_DO_BUILD_DURING_DEPLOYMENT" is set to true (default)

  3. Manual installation in startup:

    pip install -r /home/site/wwwroot/backend/requirements.txt && gunicorn --bind=0.0.0.0:8000 --worker-class eventlet --workers=1 app:app

Recommended Configuration

For TopicsFlow with WebSocket support, use:

Startup Command:

cd /home/site/wwwroot/backend && pip install --no-cache-dir -r requirements.txt && gunicorn --bind=0.0.0.0:8000 --worker-class eventlet --workers=1 --timeout=120 --access-logfile - --error-logfile - app:app

This ensures:

  1. Dependencies are installed before starting
  2. Eventlet worker is used for WebSocket support
  3. Single worker (required for eventlet with SocketIO)
  4. Proper logging

Verify Installation

After deployment, check logs to verify:

  • eventlet is installed
  • Gunicorn starts successfully
  • No import errors