Root cause: Both RequestLoggingMiddleware and ErrorLoggingMiddleware used BaseHTTPMiddleware and re-raised exceptions. When an exception (like a 401 from auth) was re-raised, the response never flowed back through CORSMiddleware, so browsers received error responses without CORS headers. This made 401 errors appear as CORS errors, breaking session resume and other operations after token expiry. Fix: Both middlewares now catch exceptions and return JSONResponse objects (with correct status codes from HTTPException) instead of re-raising. This ensures responses always flow through CORSMiddleware and receive proper Access-Control-Allow-Origin headers. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Troubleshooting Decision Tree - Backend API
FastAPI backend for the Troubleshooting Decision Tree application.
Quick Start
1. Set up Python environment
cd backend
python -m venv venv
# Windows
venv\Scripts\activate
# macOS/Linux
source venv/bin/activate
pip install -r requirements.txt
2. Start PostgreSQL database
Using Docker:
docker-compose up -d
Or install PostgreSQL locally and create a database:
CREATE DATABASE decision_tree;
3. Configure environment
Copy the example env file and update as needed:
cp .env.example .env
4. Run database migrations
alembic upgrade head
5. Start the server
uvicorn app.main:app --reload --host 0.0.0.0 --port 8000
The API will be available at:
- API: http://localhost:8000
- Docs: http://localhost:8000/api/docs
- ReDoc: http://localhost:8000/api/redoc
API Endpoints
Authentication
POST /api/v1/auth/register- Register new userPOST /api/v1/auth/login- Login (form data)POST /api/v1/auth/login/json- Login (JSON body)POST /api/v1/auth/refresh- Refresh tokenGET /api/v1/auth/me- Get current userPOST /api/v1/auth/logout- Logout
Trees
GET /api/v1/trees- List all treesGET /api/v1/trees/categories- List categoriesGET /api/v1/trees/search?q=query- Search treesGET /api/v1/trees/{id}- Get specific treePOST /api/v1/trees- Create tree (engineer/admin)PUT /api/v1/trees/{id}- Update tree (engineer/admin)DELETE /api/v1/trees/{id}- Delete tree (admin)
Sessions
GET /api/v1/sessions- List user's sessionsGET /api/v1/sessions/{id}- Get specific sessionPOST /api/v1/sessions- Start new sessionPUT /api/v1/sessions/{id}- Update sessionPOST /api/v1/sessions/{id}/complete- Complete sessionPOST /api/v1/sessions/{id}/export- Export session
Development
Create new migration
alembic revision --autogenerate -m "description"
Run migrations
alembic upgrade head
Rollback migration
alembic downgrade -1
Project Structure
backend/
├── alembic/ # Database migrations
│ └── versions/
├── app/
│ ├── api/
│ │ ├── endpoints/ # API route handlers
│ │ ├── deps.py # Dependencies (auth, etc.)
│ │ └── router.py # Main router
│ ├── core/
│ │ ├── config.py # Settings
│ │ ├── database.py # DB connection
│ │ └── security.py # JWT, password hashing
│ ├── models/ # SQLAlchemy models
│ ├── schemas/ # Pydantic schemas
│ └── main.py # FastAPI app
├── tests/
├── alembic.ini
├── docker-compose.yml
├── requirements.txt
└── README.md