# Host csv import tool with Rails: relational workflow state

Deploy a csv import tool built with Rails on Ample using the transactional workflows pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL. Verified on Rails: an optimistic version check and an event row written in the same transaction, a stale update rejected, and a history query over the application-owned events (history=2 conflict=rejected). Not separately tested: your domain records, validation rules and concurrency policy; treat the csv import tool-specific behavior as your application code.

## Prerequisites
- A Rails project that builds and starts with the documented commands (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)
- A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env)
- An Ample account token with servers:write, databases:read

## Workflow Steps
1. **Build and start**  
   `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. The server must bind 0.0.0.0 on PORT.`  
2. **Implement the pattern on PostgreSQL**  
   `The fixture's module implements transactional workflows: an optimistic version check and an event row written in the same transaction, a stale update rejected, and a history query over the application-owned events (history=2 conflict=rejected). Copy the approach into your schema; keep migrations idempotent and run them with --release-command.`  
3. **Deploy**  
   `Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked). Re-running with no change is a no-op.`  
   Command: `ample deploy . --name  --public`  
4. **Verify**  
   `Fetch the live URL and the pattern self-test route(s) (/p/transactional-workflows) from the example; then run your own checks. On failure read ample logs --kind build then --kind runtime.`  
   Command: `ample logs --kind build`

## 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**: s-1vcpu-1gb ($5.0/month)  
  - **Managed PostgreSQL database**: s-1vcpu-1gb ($5.0/month)

## Limitations
- Verified on the ruby-3.4 template at s-1vcpu-1gb with the example fixture; other sizes, templates and Rails major versions are not verified.
- The csv import tool itself (your domain records, validation rules and concurrency policy) is application code and was not separately tested; the pattern checks are what was verified.
- 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.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified; apps and their databases are placed together.

## Examples
- **Rails pattern fixture**  
  Multi-pattern Rails app whose transactional workflows module was checked live; the module is under tests/deploy-canaries/_pattern-modules.  
  Source Reference: tests/deploy-canaries/rails-patterns

## Success Checks
- **App responds on its public URL**  
  Check Kind: http_get  
  Path: /  
  Expect: ample canary rails patterns
- **Transactional-workflows self-test**  
  Check Kind: http_get  
  Path: /p/transactional-workflows  
  Expect: tx=ok history=2 conflict=rejected

## Evidence Summary
- **Canary run**: Rails pattern fixture deployed on Ample (checks passed for transactional-workflows and configuration-secrets).
- **Canary run**: The same Rails app deployed with a --release-command migration; the marker it created was readable after activation.