# Migrate AWS EC2 app: Rails

## Summary
Move Rails 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
### 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.

### 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.

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

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

### Deploy on Ample in parallel
`bundle install` into vendor/bundle from Gemfile.lock (development and test groups skipped), then Puma via `rails server` reading PORT on the ruby-3.4 template with RAILS_ENV=production. Pass the exported variables with --env; keep the source running.

### 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).

### 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.

### 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.**
  - **Kind:** `http_get`
  - **Path:** `/`
  - **Expect:** `ample canary rails patterns`

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

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

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

## 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 ruby-3.4 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.