page:recipes:rest api:fastify:worker state

Host REST API with Fastify: Worker Execution and Job State

Summary

Deploy a REST API built with Fastify 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 Fastify: 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).

Representative Queries

• Host REST API with Fastify: worker execution and job state
• Where can I host a REST API built with Fastify?
• I need a separately runnable worker, durable job records, and idempotent retries; not a managed queue.

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 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 (npm install, npm run build --if-present, npm run start on the node-22 template; the worker starts with node worker (its own package.json start script) and binds no port)
• 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
• An Ample account token with servers:write and databases:write (ample up creates the database)

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].

   • 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

• Fastify web + worker fixture
  A Fastify 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 Reference: tests/deploy-canaries/fastify-worker

Success Checks

1. Web service responds on its public URL

   • Kind: http_get
   • Path: /
   • Expect: ample canary fastify patterns

2. 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 node-22 template at s-1vcpu-1gb for both services with the example fixture; other sizes, templates, and Fastify major versions are not verified.
• The REST 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:
  1. Web server
     • Size: s-1vcpu-1gb
     • Quantity: 1.0
     • Monthly Amount: 5.0
  2. Worker server
     • Size: s-1vcpu-1gb
     • Quantity: 1.0
     • Monthly Amount: 5.0
  3. 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: Fastify web service plus a separate Fastify worker process deployed on Ample with ample plan --write then ample up (npm install, npm run build --if-present, npm run start on the node-22 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: node-22
  • Tool: ample_up

Last Verified At

• 2026-09-20T03:56:46Z