## Migrate DigitalOcean Droplet app: FastAPI

Move FastAPI compute from DigitalOcean Droplet 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: Collect the process environment from the droplet (systemd unit, PM2 or supervisor config) into an env file kept out of the repository. Not migrated automatically: Cron jobs, local upload directories and firewall rules are not migrated; move uploads to a bucket and data to a managed database. Cutover: Add the custom domain with `ample domain add`, update DNS from the droplet IP, keep the droplet until verified, then power it off. Rollback: keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

### Prerequisites
- Authorized access to the DigitalOcean Droplet 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

### Workflow Steps
1. **Inventory the source**  
List what DigitalOcean Droplet app provides beyond the component you are moving. Out of scope here: Cron jobs, local upload directories, and firewall rules are not migrated; move uploads to a bucket and data to a managed database.

2. **Source step 1**  
Collect the process environment from the droplet (systemd unit, PM2 or supervisor config) into an env file kept out of the repository.

3. **Source step 2**  
Replace the droplet's process manager and reverse proxy with the repository's start command; Ample provides HTTPS and supervision.

4. **Source step 3**  
Inventory what else runs on the droplet: databases, cron, local uploads.

5. **Deploy on Ample in parallel**  
`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 droplet IP, keep the droplet until verified, then power it off.

8. **Rollback**  
Point DNS or configuration back to the source. The source was never modified; deletion is a separate, user-executed step after validation.

### Success Checks
- Destination app responds on its public URL
- Configuration-secrets check from the destination example
- Relational-records check from the destination example
- Data or object counts and checksums match the source

### Limitations
- Documentation only: nothing is executed automatically and no execution binding is offered.
- The source-side procedure is documented from DigitalOcean Droplet app's standard tooling and was not executed in this catalog's evidence; the destination side was verified with the pattern fixture.
- Verified on the python-3.12 template at s-1vcpu-1gb; region, compliance, and request-duration limits are unknown.

### Examples
- **FastAPI pattern fixture (destination)**: Verified destination basis: FastAPI compute.

### Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 10.0
- **Components**:
  - App server: s-1vcpu-1gb (monthly amount: 5.0)
  - Managed PostgreSQL database: s-1vcpu-1gb (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.

### Evidence Summary
- The source-side export from DigitalOcean Droplet app is documented from the vendor's standard tooling and was not executed by this catalog's evidence.