page:guides:fastapi:build and start

Configure build and start for FastAPI

Summary

Configure build and start for a FastAPI app on Ample. Start uvicorn from a small run.py that reads PORT; pass --start "python3 run.py" because Python start commands are not inferred. 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

Workflow Steps

1. Make the start command bind correctly
   Start uvicorn from a small run.py that reads PORT; pass --start "python3 run.py" because Python start commands are not inferred.

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.

   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.

   ample logs  --kind build
   

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.
• Dependencies install with pip into .ample/python from requirements.txt; pyproject-only projects use uv when available.

Cost Estimate

• Monthly Amount: $5.00
• Currency: USD
  Apps and managed databases auto-pause when idle; the estimate is the always-on monthly price of the tested sizes. Plan quotas and budgets apply.

Success Checks

• Page or root route responds:
  • Kind: http_get
  • Path: /
  • Expect: ample canary fastapi basic

Examples

• fastapi-basic canary
  FastAPI app started with uvicorn.

Evidence Summary

• FastAPI app installed with pip into .ample/python and started with uvicorn on python-3.12; / and /health served correctly.

Next Actions

• Browse the catalog index.
• Search published recipes by intent, stack and constraints.
• Prepare a side-effect-free deployment plan for an authorized project.