# Migrate Fly.io app: FastAPI

## Summary
Move FastAPI compute from Fly.io app to Ample, one component at a time. Destination verified on Ample: the app built, started and answered on its public HTTPS URL with encrypted configuration delivered. Source procedure: Export secrets and env from `fly.toml` [env] and `fly secrets list` (values must come from your own records; Fly does not reveal secret values). Not migrated automatically: Multi-region placement, Fly Machines API, volumes and 6PN private networking are not migrated; region is an unknown fact on Ample. Cutover: Add the custom domain with `ample domain add`, update DNS from the Fly target, keep the Fly app until verified, then scale it to zero. Rollback: keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

## Prerequisites
- Authorized access to the Fly.io app source and its export tooling
- An inventory of every component in scope and out of scope
- A validated backup or copy before any cutover
- An Ample account token with servers:write, databases:read

## Infrastructure Requirements
### Compute
* **Primitive ID**: primitive:compute  
* **Label**: Compute  
* **Status**: verified  
* **Summary**: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.

### Postgres
* **Primitive ID**: primitive:postgres  
* **Label**: Postgres  
* **Status**: verified  
* **Summary**: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

## Workflow Steps
1. **Inventory the source**  
   List what Fly.io app provides beyond the component you are moving. Out of scope here: Multi-region placement, Fly Machines API, volumes and 6PN private networking are not migrated; region is an unknown fact on Ample.
2. **Source step 1**  
   Export secrets and env from `fly.toml` [env] and `fly secrets list` (values must come from your own records; Fly does not reveal secret values).
3. **Source step 2**  
   Translate `fly.toml` services and the Dockerfile or buildpack into a Node or Python source deploy; Ample builds from source on its templates.
4. **Source step 3**  
   Note Fly-only features in use: multi-region placement, machines API, volumes, private networking.
5. **Deploy on Ample in parallel**  
   pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template. Pass the exported variables with --env; keep the source running.  
   Command: `ample deploy . --name  --public --start "python3 run.py" --env-file .env.production`.
6. **Validate before cutover**  
   Run the app's own checks and, for data, compare counts and checksums; the example checks are the pattern self-tests (/p/configuration-secrets, /p/relational-records).
7. **Cut over**  
   Add the custom domain with `ample domain add`, update DNS from the Fly target, keep the Fly app until verified, then scale it to zero.
8. **Rollback**  
   Point DNS or configuration back to the source. The source was never modified; deletion is a separate, user-executed step after validation.

## Limitations
- Documentation only: nothing is executed automatically and no execution binding is offered.
- The source-side procedure is documented from Fly.io app's standard tooling and was not executed in this catalog's evidence; the destination side was verified with the pattern fixture.
- No full source-product parity is claimed: Multi-region placement, Fly Machines API, volumes and 6PN private networking are not migrated; region is an unknown fact on Ample.
- Verified on the python-3.12 template at s-1vcpu-1gb; region, compliance and request-duration limits are unknown.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures on the managed side are not verified beyond the pattern checks.

## Cost Estimate
- **Currency**: USD  
- **Monthly Amount**: 10.0  
- **Authoritative**: true  
- **Basis**: size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty  
- **Components**:  
  * **Name**: app server  
    * **Size**: s-1vcpu-1gb  
    * **Quantity**: 1.0  
    * **Monthly Amount**: 5.0  
  * **Name**: managed PostgreSQL database  
    * **Size**: s-1vcpu-1gb  
    * **Quantity**: 1.0  
    * **Monthly Amount**: 5.0  
- **Note**: Destination always-on monthly price of the tested sizes; apps auto-pause when idle. Source costs are unknown to Ample.

## Examples
- **Title**: FastAPI pattern fixture (destination)  
  **Description**: Verified destination basis: FastAPI compute.  
  **Source Reference**: tests/deploy-canaries/fastapi-patterns

## Success Checks
1. **Description**: destination app responds on its public URL  
   **Kind**: http_get  
   **Path**: /  
   **Expect**: ample canary fastapi patterns
2. **Description**: configuration-secrets check from the destination example  
   **Kind**: http_get  
   **Path**: /p/configuration-secrets  
   **Expect**: see the pattern fixture checks
3. **Description**: relational-records check from the destination example  
   **Kind**: http_get  
   **Path**: /p/relational-records  
   **Expect**: see the pattern fixture checks
4. **Description**: data or object counts and checksums match the source  
   **Kind**: manual  
   **Expect**: operator comparison before cutover.