page:recipes:event registration:phoenix:relational workflow

Host event registration with Phoenix: relational workflow state

Summary

Deploy an event registration built with Phoenix 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 Phoenix: 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 event registration-specific behavior as your application code.

Representative Queries

• Host event registration with Phoenix: relational workflow state
• Where can I host Event registration built with Phoenix?
• I need a domain record schema, validation rules and concurrency behavior.

Resource Requirements

• primitive:compute
• primitive:postgres

Infrastructure Requirements

• Compute: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
• Postgres: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.

Prerequisites

1. A Phoenix project that builds and starts with the documented commands (mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs).
2. A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env).
3. An Ample account token with servers:write, databases:read.

Workflow Steps

1. Build and start: mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs. The server must bind 0.0.0.0 on PORT.
2. Implement the pattern on PostgreSQL: 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: ample deploy . --name --public.
4. Verify: Fetch the live URL and the pattern self-test route(s) from the example; then run your own checks: ample logs --kind build then --kind runtime.

Examples

• Phoenix pattern fixture: Multi-pattern Phoenix app whose transactional workflows module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

Success Checks

1. App responds on its public URL: http_get path: /, expect: ample canary phoenix patterns.
2. Transactional-workflows self-test: http_get path: /p/transactional-workflows, expect: tx=ok history=2 conflict=rejected.

Limitations

• Verified on the elixir-1.18 template at s-1vcpu-1gb with the example fixture; other sizes, templates and Phoenix major versions are not verified.
• The event registration itself (your domain records, validation rules and concurrency policy) is application code and was not separately tested; the pattern checks are what was verified.

Cost Estimate

• Monthly Amount: 10.0 USD
• 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

Evidence Summary

• Canary run results: Phoenix pattern fixture deployed on Ample (mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; checks passed for transactional-workflows and configuration-secrets).

Next Actions

1. Browse the catalog index: GET /v1/catalog
2. Search published recipes by intent, stack and constraints: POST /v1/catalog/search
3. Prepare a side-effect-free deployment plan for an authorized project: POST /v1/catalog/plan
4. Read the existing agent authentication setup: GET /mcp/setup
5. Browse Event registration: GET /v1/catalog/nodes/workload%3Aevent-registration
6. Browse Phoenix: GET /v1/catalog/nodes/stack%3Aframework-phoenix
7. Browse Transactional workflows: GET /v1/catalog/nodes/pattern%3Atransactional-workflows
8. Browse Deploy web app: GET /v1/catalog/nodes/intent%3Adeploy-web-app