## Host ai workflow runner with FastAPI: Postgres-backed state

### Summary
Deploy a ai workflow runner built with FastAPI on Ample using the durable job state 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: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true). Not separately tested: your job types, payload schema and retry policy; treat the ai workflow runner-specific behavior as your application code.

### Representative Queries
- Host ai workflow runner with FastAPI: Postgres-backed state
- Where can I host AI workflow runner built with FastAPI?
- I need a durable state schema and retry/recovery semantics implemented by application code.

### Resource Requirements
- Compute
- Postgres

### Infrastructure Requirements
1. ### Compute
   - **Status**: verified  
   - **Summary**: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.

2. ### Postgres
   - **Status**: verified  
   - **Summary**: 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
- 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.

### 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 durable job state: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true). 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.  
   ```sh
   ample deploy . --name  --public --start "python3 run.py"
   ```

4. **Verify**  
   Fetch the live URL and the pattern self-test route(s) (/p/durable-job-state) from the example; then run your own checks. On failure read `ample logs  --kind build` then `--kind runtime`.  
   ```sh
   ample logs  --kind build
   ```

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

- **Durable-job-state self-test**  
  - **Kind**: http_get  
  - **Path**: /p/durable-job-state  
  - **Expect**: job=done attempts=1 idempotent=true

### 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 ai workflow runner itself (your job types, payload schema and retry 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.

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

### Last Verified At
2026-09-21T01:14:18Z

### Evidence Summary
- **Canary Run**: FastAPI pattern fixture deployed on Ample. Checks passed for durable-job-state and configuration-secrets.

### Formats
- [HTML Format](/content/recipes/ai-workflow-runner/fastapi/persistent-state/index.html)  
- [Markdown Format](/content/recipes/ai-workflow-runner/fastapi/persistent-state.md)  
- [JSON Format](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Aai-workflow-runner%3Afastapi%3Apersistent-state)