# Host GraphQL API with FastAPI: Worker Execution and Job State

Deploy a GraphQL API built with FastAPI as a public web service plus a dedicated worker process on Ample. `ample plan --write` discovers both services and their shared database and writes ample.toml; `ample up` reconciles the topology: a managed PostgreSQL 16 database, a public web microVM and a private worker microVM (kind worker, no public URL), both reading DATABASE_URL. Verified on FastAPI: a separately deployed worker service (kind worker, no public URL) sharing a declared managed PostgreSQL database with the web service, consuming a jobs table with row locks and marking jobs done once (worker=done attempts=1). Not separately tested: your job payloads, retry policy and scheduling; treat the GraphQL API-specific behavior as your application code.

## Representative Queries
- Host GraphQL API with FastAPI: worker execution and job state
- Where can I host GraphQL API built with FastAPI?
- I need a separately runnable worker, durable job records and idempotent retries; not a managed queue.

## Resource Requirements
- Compute
- PostgreSQL

## 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.

## Framework
- FastAPI

## Workload
- GraphQL API

## Release Status
- Published

## Support Status
- Verified

## Execution Status
- Ready

## Prerequisites
1. A repository with the web app and the worker as separate service directories (the fixture uses apps/web and apps/worker), each building and starting 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; the worker starts with python3 worker.py and binds no port).
2. Both services read DATABASE_URL at runtime and share one jobs table; the worker claims rows with SELECT ... FOR UPDATE SKIP LOCKED and marks them done once.
3. An Ample account token with servers:write and databases:write (ample up creates the database).

## 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. **Plan the topology**  
   Run the planner once. It discovers the web and worker services, infers kind = "worker" for the process without a port, declares the database each service needs, and writes ample.toml. Exit 2 means it left questions in the manifest; answer them with --answer or by editing the file.
   - Command: `ample plan --write .`

2. **Share one database**  
   Keep a single [databases.main] with engine = "postgres", drop any per-service database the planner added, and set DATABASE_URL = { database = "main" } under both [services.web.env] and [services.worker.env]. Python services also need an explicit start command in the manifest (the fixture sets start for both services).
   - Command: `ample plan --offline .`

3. **Apply**  
   Reconcile the whole manifest in dependency order: the database first, then both services. It is idempotent and never destructive; exit 0 means everything applied, 2 needs input, 1 a failed resource (independent siblings still proceed and re-running resumes).
   - Command: `ample up .`

4. **Verify**  
   Fetch the web service URL and its worker status route (/p/worker-queue/status in the example) and confirm the worker processed the enqueued job; on failure read the worker service's runtime logs.
   - Command: `ample logs --kind runtime`

## Examples
- **FastAPI web + worker fixture**  
  A FastAPI web app (apps/web) and a worker process (apps/worker) sharing one managed PostgreSQL database; the queue module is under tests/deploy-canaries/_pattern-modules.
  - Source Ref: tests/deploy-canaries/fastapi-worker

## Success Checks
- **Web service responds on its public URL**  
  - Kind: http_get  
  - Path: /  
  - Expect: ample canary fastapi patterns
- **Worker consumed the enqueued job**  
  - Kind: http_get  
  - Path: /p/worker-queue/status  
  - Expect: worker=done attempts=1 result=processed-by-worker

## Limitations
- Verified on the python-3.12 template at s-1vcpu-1gb for both services with the example fixture; other sizes, templates and FastAPI major versions are not verified.
- The GraphQL API itself (your job payloads, retry policy and scheduling) is application code and was not separately tested; the worker-queue check is what was verified.
- The worker is a single long-running process supervised in its own microVM; there is no scheduler, cron or horizontal worker scaling in this recipe, and the check ran immediately after deploy so idle behavior of the worker VM is not verified.
- The worker service is private: it has no public URL and is reached only through the shared database; both services are placed with their database.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified; apps and their databases are placed together.
- Region, compliance attestations and request-duration limits are unknown and not claimed.

## Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 15.0
- **Authoritative**: true
- **Basis**: size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty
- **Components**:
  - **Web server**:  
    - Size: s-1vcpu-1gb  
    - Quantity: 1.0  
    - Monthly Amount: 5.0  
  - **Worker 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  
- **Note**: Always-on monthly price of the tested sizes for the web service, the worker service and the database; apps auto-pause when idle.

## Evidence Summary
- **Kind**: canary_run
  - **Summary**: FastAPI web service plus a separate Python worker process deployed on Ample with `ample plan --write` then `ample up` (pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template); the web service enqueued a job that the private worker service consumed from the shared managed PostgreSQL database. Pattern proof: a separately deployed worker service (kind worker, no public URL) sharing a declared managed PostgreSQL database with the web service, consuming a jobs table with row locks and marking jobs done once (worker=done attempts=1).
  - **Observed At**: 2026-09-20T03:56:46Z
  - **Implementation Revision**: 03b6402b1b3e19178985f08ea4033804521d85d4-dirty (CLI b75e104)
  - **Expires At**: 2027-03-19T03:56:46Z
  - **Scope**:  
    - **Checks**: ["/","/p/worker-queue/status"]  
    - **Pattern**: pattern:dedicated-worker-process  
    - **Services**: ["web","worker"]  
    - **Template**: python-3.12  
    - **Tool**: ample_up

## Last Verified At
- 2026-09-20T03:56:46Z

## Next Actions
1. **Action ID**: browse-catalog  
   - **Label**: Browse the catalog index  
   - **Operation ID**: catalog_index  
   - **Method**: GET  
   - **Relative Path**: /v1/catalog
2. **Action ID**: search-recipes  
   - **Label**: Search published recipes by intent, stack and constraints  
   - **Operation ID**: search_recipes  
   - **Method**: POST  
   - **Relative Path**: /v1/catalog/search  
   - **Parameters**: {"body":{"limit":5,"query":"Host graphql api with FastAPI: worker execution and job state"}}
3. **Action ID**: plan:page:recipes:graphql-api:fastapi:worker-state  
   - **Label**: Prepare a side-effect-free deployment plan for an authorized project  
   - **Operation ID**: plan_deployment  
   - **Method**: POST  
   - **Relative Path**: /v1/catalog/plan  
   - **Parameters**: {"body":{"inputs":{},"projectId":"","recipeId":"page:recipes:graphql-api:fastapi:worker-state","recipeRevision":"r1"}}
4. **Action ID**: auth-setup  
   - **Label**: Read the existing agent authentication setup  
   - **Operation ID**: existing_auth_setup  
   - **Method**: GET  
   - **Relative Path**: /mcp/setup
5. **Action ID**: browse:workload:graphql-api  
   - **Label**: Browse GraphQL API  
   - **Operation ID**: browse_node  
   - **Method**: GET  
   - **Relative Path**: /v1/catalog/nodes/workload%3Agraphql-api
6. **Action ID**: browse:stack:framework-fastapi  
   - **Label**: Browse FastAPI  
   - **Operation ID**: browse_node  
   - **Method**: GET  
   - **Relative Path**: /v1/catalog/nodes/stack%3Aframework-fastapi
7. **Action ID**: browse:pattern:dedicated-worker-process  
   - **Label**: Browse Dedicated worker process  
   - **Operation ID**: browse_node  
   - **Method**: GET  
   - **Relative Path**: /v1/catalog/nodes/pattern%3Adedicated-worker-process
8. **Action ID**: browse:intent:deploy-api  
   - **Label**: Browse Deploy API  
   - **Operation ID**: browse_node  
   - **Method**: GET  
   - **Relative Path**: /v1/catalog/nodes/intent%3Adeploy-api