## Host ai chat application with Spring Boot: worker execution and job state

### Summary
Deploy an AI chat application 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 AI chat application-specific behavior as your application code.

### Resource 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.

### 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 (./mvnw -q -DskipTests package (or the Gradle wrapper) producing one application jar, then `java -jar` on the jvm-21 template (Temurin JDK 21) with server.port read from PORT; the worker starts with `java -jar` of its own Maven module (plain JDBC) 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
- **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
- **Worker consumed the enqueued job**

### 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 AI chat application 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.

### Cost Estimate
- **Monthly Amount**: $15.00
- **Basis**: size prices from pricing.toml at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty

| Component                       | Size                     | Quantity | Monthly Amount    |
|---------------------------------|-------------------------|----------|-------------------|
| Web server                      | s-1vcpu-1gb            | 1.0      | $5.00             |
| Worker server                   | s-1vcpu-1gb            | 1.0      | $5.00             |
| Managed PostgreSQL database     | s-1vcpu-1gb            | 1.0      | $5.00             |

> 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
- **Spring Boot web service plus a separate Spring Boot worker process** deployed on Ample with `ample plan --write` then `ample up`, consuming a jobs table with row locks and marking jobs done once (worker=done attempts=1).

### Last Verified At
- 2026-09-20T22:41:46Z