I am facing an issue when deploying my Flask application on Railway. The app fails to start, and I receive the following error:

ModuleNotFoundError: No module named 'MySQLdb'


[2025-02-04 16:27:43 +0000] [6] [INFO] Worker exiting (pid: 6)

[2025-02-04 16:27:43 +0000] [1] [ERROR] Worker (pid:4) exited with code 3

[2025-02-04 16:27:43 +0000] [1] [ERROR] Worker (pid:5) was sent SIGTERM!

[2025-02-04 16:27:43 +0000] [1] [ERROR] Worker (pid:6) was sent SIGTERM!

[2025-02-04 16:27:43 +0000] [1] [ERROR] Worker (pid:7) was sent SIGTERM!

[2025-02-04 16:27:43 +0000] [1] [ERROR] Shutting down: Master

[2025-02-04 16:27:43 +0000] [1] [ERROR] Reason: Worker failed to boot.

The full stack trace shows that SQLAlchemy is trying to use the MySQLdb driver, despite having PyMySQL installed and specified in my requirements.txt.

Environment Setup

• Tech stack:

• Flask (version: 2.3.3)

• Flask-SQLAlchemy (version: 3.1.1)

• Gunicorn (version: 23.0.0)

• PyMySQL (version: 1.1.0)

• SQLAlchemy (version: 2.0.37)

• Project structure:

├── backend
│   └── app.py (Flask app definition)
├── main.py (entry point, imports app from backend.app)
├── requirements.txt
└── nixpacks.toml

• Current DATABASE_URL: The environment variable DATABASE_URL is set in Railway's settings but does not specify the pymysql driver.

Steps Taken to Fix

1. Updated `DATABASE_URL

2. Verified that PyMySQL is installed via requirements.txt.

3. Updated the Gunicorn command in the custom start command:

   gunicorn backend.app:app --workers 4 --bind 0.0.0.0:$PORT

4. Tested locally, and the app works without issues.

Could you confirm whether Railway supports mysql+pymysql?
Is there anything else I need to configure in the deployment process to resolve this issue?
Any suggestions for further debugging?

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