Running FastAPI on Azure Web APP - gateway timeout

I em trying to run a FastAPI on Azure Web App. But getting following error:

azure 504.0 GatewayTimeout

When I look in the logs I get following error:

Any suggestions what can cause this?

name: Build and deploy Python app to Azure Web App - segato-fast-api

on:
  push:
    branches:
      - dev
  workflow_dispatch:

jobs:
  build:
    runs-on: ubuntu-latest

    steps:
      - uses: actions/checkout@v4

      - name: Set up Python version
        uses: actions/setup-python@v5
        with:
          python-version: '3.12'

      - name: Create and start virtual environment
        run: |
          python -m venv venv
          source venv/bin/activate
      
      - name: Install dependencies
        run: pip install -r requirements.txt
        
      # Optional: Add step to run tests here (PyTest, Django test suites, etc.)

      - name: Zip artifact for deployment
        run: zip release.zip ./* -r

      - name: Upload artifact for deployment jobs
        uses: actions/upload-artifact@v4
        with:
          name: python-app
          path: |
            release.zip
            !venv/
  deploy:
    runs-on: ubuntu-latest
    needs: build
    environment:
      name: 'Production'
      url: ${{ steps.deploy-to-webapp.outputs.webapp-url }}
    permissions:
      id-token: write #This is required for requesting the JWT

    steps:
      - name: Download artifact from build job
        uses: actions/download-artifact@v4
        with:
          name: python-app

      - name: Unzip artifact for deployment
        run: unzip release.zip

      
      - name: Login to Azure
        uses: azure/login@v2
        with:
          client-id: ${{ secrets.AZUREAPPSERVICE_CLIENTID_B7A634A93F634F01A9CEAF7F209FCFD4 }}
          tenant-id: ${{ secrets.AZUREAPPSERVICE_TENANTID_085412552C7445619A1BD2878A692F63 }}
          subscription-id: ${{ secrets.AZUREAPPSERVICE_SUBSCRIPTIONID_B0970C502F86483D9551067BC403A7CA }}

      - name: 'Deploy to Azure Web App'
        uses: azure/webapps-deploy@v3
        id: deploy-to-webapp
        with:
          app-name: 'segato-fast-api'
          slot-name: 'Production'
          
Add or update the Azure App Service build and deployment workflow config · hafnia-dna/dna-port-api@561d351 

from fastapi import FastAPI,Request
from fastapi.middleware.cors import CORSMiddleware
from fastapi_azure_auth import SingleTenantAzureAuthorizationCodeBearer
import uvicorn
from fastapi import FastAPI, Security

from settings import Settings


from contextlib import asynccontextmanager
from typing import AsyncGenerator

from enums import settings

from routers.router1 import router1_router
from routers.docs import tags_metadata

from utils.azure.azure_auth import AzureAuth
from utils.azure.azure_logging import azure_logger 

azure_auth = AzureAuth()
@asynccontextmanager 
async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]: 
    await azure_auth.load_openid_config() 
    yield


app = FastAPI(
    openapi_tags=tags_metadata,
    swagger_ui_oauth2_redirect_url='/oauth2-redirect',
    swagger_ui_init_oauth={
        'usePkceWithAuthorizationCodeGrant': True,
        'clientId': settings.OPENAPI_CLIENT_ID,
        'scopes': settings.SCOPE_NAME,
    },
)

app.include_router(router1_router)

if settings.BACKEND_CORS_ORIGINS:
    app.add_middleware(
        CORSMiddleware,
        allow_origins=[str(origin) for origin in settings.BACKEND_CORS_ORIGINS],
        allow_credentials=True,
        allow_methods=['*'],
        allow_headers=['*'],
)

if __name__ == '__main__':
        uvicorn.run('main:app', reload=True)

Configuration:

these 504 error mostly means the container does not startup. likely code crashed on startup. my suggestion is to retrieve more error logs than what you can see in the log stream. what i usually do is to connect to the app service via VS code's azure app service extension, then you will see a detailed container log file here. it usually tells you the initial crash exception. You should be able to see the same logs using kudo console.