hello-rio

The canonical Rust-authored caixa Servico. Companion to programs/hello-world (the Lisp-authored canonical Servico). Both serve identical JSON, both render to the same Kubernetes ComputeUnit shape — they prove that caixa is source-language-agnostic for service-class packages.

What it does

A WASI 0.2 HTTP component, ~50 LoC of Rust on top of wstd. Compiled to wasm32-wasip2, runnable directly in wasmtime serve. Three GET routes:

route	response
/healthz	{"status":"ok","served-by":"hello-rio","module-version":"v0.1.0"}
/	{"message":"<GREETING>, <AUDIENCE><PUNCTUATION>","served-by":"hello-rio"}
/hello	(alias for /)

Env knobs: GREETING, AUDIENCE, PUNCTUATION (defaults: Hello, rio, !).

Layout

caixa.lisp                            ← (defcaixa :kind Servico …) — typed manifest
servicos/hello-rio.computeunit.yaml   ← K8s ComputeUnit runtime contract
src/main.rs                           ← Rust source — wasm32-wasip2 component
Cargo.toml                            ← wstd + wasi
flake.nix                             ← substrate's wasi-service-flux-flake

Build

nix build .#wasmModule       # → result/lib/hello-rio.wasm
nix build .#dockerImage      # → wasmtime + .wasm OCI tarball
nix build .#bundle           # → standalone FluxCD HelmRelease bundle

Run

# Local (wasmtime as the runtime):
wasmtime serve --addr 127.0.0.1:8080 \
  --env GREETING=Hello --env AUDIENCE=world --env PUNCTUATION=! \
  $(nix build .#wasmModule --no-link --print-out-paths)/lib/hello-rio.wasm

curl localhost:8080/hello
# → {"message":"Hello, world!","served-by":"hello-rio"}

Publish

feira publish              # tag v0.1.0 + push to origin (Zig-style git-tag)

Deploy to rio

nix run .#render-deploy    # render FluxCD bundle
nix run .#deploy-rio       # render + git commit + push to k8s repo

FluxCD reconciles. Once lareira-tatara-stack is unsuspended on rio, the wasm-operator picks up servicos/hello-rio.computeunit.yaml directly and the standalone HelmRelease retires.

Why "rio"

rio is the K3s cluster on a NixOS node in Bristol — the canonical single-node fleet member. Every fleet hostname follows ${app}.${cluster}.${location}.${domain}, so this service lives at hello-rio.rio.bristol.quero.cloud once deployed (the shorter hello-rio.quero.cloud is its public ingress).

License

MIT — see LICENSE.