# Host form collection with FastAPI: relational workflow state

Deploy a form collection built with FastAPI 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 FastAPI: 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 form collection-specific behavior as your application code.

## Representative Queries
- Host form collection with FastAPI: relational workflow state
- Where can I host Form collection built with FastAPI?
- I need a domain record schema, validation rules and concurrency behavior.

## Prerequisites
- A FastAPI project that builds and starts with the documented commands (pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template)
- 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

## Tested Configuration
- **Template:** python-3.12
- **Runtime:** python
- **Size:** s-1vcpu-1gb
- **Install:** python3 -m pip install --target .ample/python -r requirements.txt
- **Start:** PYTHONPATH=.ample/python:${PYTHONPATH:-} python3 run.py

## Workflow Steps
1. **Build and start**  
   pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template. 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 --start "python3 run.py"

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

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

- **Transactional-workflows self-test**  
   - Kind: http_get  
   - Path: /p/transactional-workflows  
   - Expect: tx=ok history=2 conflict=rejected

## Cost Estimate
- **Currency:** USD
- **Monthly Amount:** 10.0
- **Note:** Always-on monthly price of the tested sizes; apps and databases auto-pause when idle.
- **Components:**  
  - **App server**: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0  
  - **Managed PostgreSQL database**: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0

## Limitations
- Verified on the python-3.12 template at s-1vcpu-1gb with the example fixture; other sizes, templates and FastAPI major versions are not verified.
- The form collection itself (your domain records, validation rules and concurrency policy) is application code and was not separately tested.
- 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.

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

## Next Actions
- **Browse the catalog index**  
   Method: GET  
   Relative Path: /v1/catalog
- **Search published recipes by intent, stack and constraints**  
   Method: POST  
   Relative Path: /v1/catalog/search  
   Body: {"limit":5,"query":"Host form collection with FastAPI: relational workflow state"}
- **Prepare a side-effect-free deployment plan for an authorized project**  
   Method: POST  
   Relative Path: /v1/catalog/plan  
   Body: {"inputs":{},"projectId":"","recipeId":"page:recipes:form-collection:fastapi:relational-workflow","recipeRevision":"r1"}
- **Read the existing agent authentication setup**  
   Method: GET  
   Relative Path: /mcp/setup