Lab 12: a quicknotes endpoint as a wasm component on spin

[Dekart-hub]

Goal

Build one QuickNotes-style endpoint (Moscow time as JSON) as a WebAssembly component with the Spin Go SDK, measure it against the Lab 6 Docker container, and (bonus) rebuild the same logic as a standalone WASI CLI module under bare wasmtime to contrast the two execution models.

Changes

• wasm/: the Spin component, scaffolded with spin new -t http-go (Spin 3.6.3, TinyGo 0.41.1, SDK spinframework/spin-go-sdk/v2 v2.2.1)
  • main.go: spinhttp.Handle handler returning unix, iso, hour_minute and the timezone as JSON; Moscow via time.FixedZone because TinyGo ships no tzdata
  • spin.toml: route scoped to /time, allowed_outbound_hosts = [], scaffold's wasip1 -buildmode=c-shared build command untouched
• wasm-cli/ (bonus): the same logic as a no-SDK WASI command module in the CGI/WAGI shape (request from env vars, headers plus JSON to stdout) for wasmtime run
• submissions/lab12.md: build and curl evidence, the full perf table, both execution models compared, design questions a-j

Testing

• spin build produces a 0.53 MB main.wasm; spin up serves /time with valid Moscow-time JSON (200, application/json, RFC3339 with +03:00); POST gets 405, unrouted paths get 404
• Perf vs the Lab 6 container on the same machine: warm p50 0.59 ms vs 1.87 ms (curl time_total, 50 runs), cold start median 57 ms vs 121 ms (5 samples, launch to first 200), artifact 0.53 MB vs 21.6 MB
• Design-question experiments run for real: dropping -buildmode=c-shared fails the link (the scaffold has no func main), the Spin component under bare wasmtime run exits silently as a reactor, and wasmtime serve refuses the core module
• Bonus module: wasmtime run --env REQUEST_METHOD=GET --env PATH_INFO=/time prints the same JSON; per-invocation p50 6.0 ms vs 0.59 ms from the warm Spin server

Checklist

• Title is a clear sentence (<= 70 chars)
• Commits are signed (git log --show-signature)
• submissions/lab12.md updated