page:recipes:rest api:flask:worker state

Host REST API with Flask: Worker Execution and Job State

Deploy a REST API built with Flask 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 Flask: 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 REST API-specific behavior as your application code.

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.

Framework

• Flask

Workload

• REST API

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 waitress from app.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)

Testing 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 app.py

Workflow Steps

1. Plan the topology: Run the planner once. It discovers the web and worker services…
   • Command: ample plan --write .
2. Share one database: Keep a single [databases.main] with engine = "postgres"…
   • Command: ample plan --offline .
3. Apply: Reconcile the whole manifest in dependency order: the database first…
   • Command: ample up .
4. Verify: Fetch the web service URL and its worker status route…
   • Command: ample logs --kind runtime

Success Checks

• Web service responds on its public URL
• Worker consumed the enqueued job

Limitations

• Verified on the python-3.12 template at s-1vcpu-1gb for both services with the example fixture…

Cost Estimate

• Currency: USD
• Monthly Amount: 15.0
• Components:
  • Web server: Size s-1vcpu-1gb, Monthly Amount: 5.0
  • Worker server: Size s-1vcpu-1gb, Monthly Amount: 5.0
  • Managed PostgreSQL database: Size s-1vcpu-1gb, 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.

Examples

• Title: Flask web + worker fixture
  • Description: A Flask 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/flask-worker

Evidence Summary

• A Flask web service plus a separate Python worker process deployed on Ample with ample plan --write then ample up…

Last Verified At

• 2026-09-20T03:56:46Z