# Host AI Chat Application with Axum: Worker Execution and Job State

## Summary
Deploy an AI chat application built with Axum 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 Axum: 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's specific behavior as your application code.

## Representative Queries
- Host AI chat application with Axum: worker execution and job state
- Where can I host AI chat application built with Axum?
- 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.

## Execution Status
Ready

## 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 (cargo build --release in the rust builder image (stable toolchain, Cargo.lock committed, pure-Rust dependencies), then the release binary on the ubuntu-24.04 template reading PORT and DATABASE_URL; the worker starts with its own release binary (plain tokio-postgres) 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. 
   - 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; 
   - 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.
   - Command: `ample logs  --kind runtime`

## Examples
### Axum web + worker fixture
- A Axum 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 (expect: `ample canary axum patterns`).
- Worker consumed the enqueued job (expect: `worker=done attempts=1 result=processed-by-worker`).

## Limitations
- Verified on the ubuntu-24.04 template at s-1vcpu-2gb for both services with the example fixture; other sizes, templates, and Axum 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.

## Cost Estimate
- **Monthly Amount**: $15.00

### Components
- Web server: size s-1vcpu-1gb, quantity 1.0, monthly amount $5.00
- Worker server: size s-1vcpu-1gb, quantity 1.0, monthly amount $5.00
- Managed PostgreSQL database: size s-1vcpu-1gb, quantity 1.0, monthly amount $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.

## Documentation
- [HTML](/content/recipes/ai-chat-application/axum/worker-state/index.html)
- [Markdown](/content/recipes/ai-chat-application/axum/worker-state.md)