# Migrate AWS EC2 app: FastAPI

## Summary
Move FastAPI compute from AWS EC2 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 instance (systemd unit or process manager config) into an env file kept out of the repository. Not migrated automatically: Cron jobs, local files on the instance disk, security-group networking and IAM instance roles are not migrated; use managed databases, buckets and encrypted env instead.

Cutover: Add the custom domain with `ample domain add`, update DNS from the instance or load balancer, keep the instance until verified, then stop it.

Rollback: keep the source untouched until you confirm; nothing at the source is changed or deleted by this guide.

## Workflow Steps
1. **Inventory the source**  
   List what AWS EC2 app provides beyond the component you are moving. Out of scope here: Cron jobs, local files on the instance disk, security-group networking and IAM instance roles are not migrated; use managed databases, buckets and encrypted env instead.

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

3. **Source step 2**  
   Replace the instance's process manager with the repository's start command; Ample supervises the process and restarts it.

4. **Source step 3**  
   Inventory what else runs on the instance: databases, cron, reverse proxy rules, local files.

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 instance or load balancer, keep the instance until verified, then stop it.

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

## Prerequisites
- Authorized access to the AWS EC2 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.

## Limitations
- Documentation only: nothing is executed automatically and no execution binding is offered.
- The source-side procedure is documented from AWS EC2 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: Cron jobs, local files on the instance disk, security-group networking and IAM instance roles are not migrated; use managed databases, buckets and encrypted env instead.
- 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  
- **Basis:** size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty  
- **Components:**  
  - App server: size s-1vcpu-1gb, quantity 1.0, monthly amount 5.0  
  - 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.

## Success Checks
1. **Destination app responds on its public URL**  
   - Kind: http_get  
   - Path: /  
   - Expect: ample canary fastapi patterns

2. **Configuration-secrets check from the destination example**  
   - Kind: http_get  
   - Path: /p/configuration-secrets  
   - Expect: see the pattern fixture checks

3. **Relational-records check from the destination example**  
   - Kind: http_get  
   - Path: /p/relational-records  
   - Expect: see the pattern fixture checks

4. **Data or object counts and checksums match the source**  
   - Kind: manual  
   - Expect: operator comparison before cutover.