### Host REST API with Spring Boot: Worker Execution and Job State

#### Summary
Deploy a REST API built with Spring Boot 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 Spring Boot: 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.

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

#### Resource Requirements
- **Compute**
- **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.

#### 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`

#### Tested Configuration
- **Template**: jvm-21
- **Runtime**: java
- **Size**: s-1vcpu-2gb
- **Build Command**: `./mvnw -q -DskipTests package`
- **Start Command**: `java -jar $(ls target/*.jar | grep -v -- '-plain' | head -n 1)`

#### Examples
- **Spring Boot web + worker fixture**: A Spring Boot 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.

#### Success Checks
- Web service responds on its public URL
  - Kind: http_get
  - Path: / 
  - Expect: ample canary spring boot 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 jvm-21 template at s-1vcpu-2gb for both services with the example fixture; other sizes, templates and Spring Boot 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.
- 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
- **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: Spring Boot web service plus a separate Spring Boot worker process deployed on Ample with `ample plan --write` then `ample up`. The web service enqueued a job that the private worker service consumed from the shared managed PostgreSQL database.
- Implemented at: 2026-09-20T22:41:46Z

#### Formats
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