page:guides:flask:build and start

Configure build and start for Flask

Summary

Configure build and start for a Flask app on Ample. Serve the WSGI app with a production server such as waitress from app.py reading PORT; pass --start "python3 app.py". Ample detects the runtime, installs dependencies, runs the build when present and starts the app on the python-3.12 template behind a public HTTPS URL.

Prerequisites

• A requirements.txt (or pyproject) and a start command that reads PORT and binds 0.0.0.0
• An Ample account token with servers:write

Tested Configuration

• Template: python-3.12
• Runtime: python
• Size: s-1vcpu-1gb
• Install: python3 -m pip install --target .ample/python -r requirements.txt
• Start: PYTHONPATH=.ample/python:${PYTHONPATH:-} python3 app.py

Workflow Steps

1. Make the start command bind correctly
   Serve the WSGI app with a production server such as waitress from app.py reading PORT; pass --start "python3 app.py".
2. Deploy
   Run the existing synchronous deploy once from the project directory and read the result. Exit 0 is live, 1 is failed, 2 is blocked on a required preflight action. Re-running with no change is a content-addressed no-op. Command: ample deploy . --name --public --format json --start "python3 run.py"
3. Verify
   Fetch the live URL and run the success checks below. On failure read the build log, then the runtime log, fix the cause and deploy again; do not blind-retry. Command: ample logs --kind build

Success Checks

• Description: page or root route responds
  Kind: http_get
  Path: /
  Expect: ample canary flask basic

Limitations

• Verified on the node-22 template at s-1vcpu-1gb; other templates and sizes are not verified by this recipe.
• Region, compliance attestations and request-duration limits are unknown and not claimed.
• Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.
• The Flask development server was not used; waitress was tested.