Serving /eula/ re-parsed the large (~122 KB) EULA markdown on every request. Under the rolling deploy's host contention (the renderer is capped at 1 CPU / 192 MB) that was slow enough that the contour /eula/ probe failed for its whole 60s retry window, while the smaller /privacy/ squeaked through; both serve fine once the host is idle. Render privacy + eula once at boot and serve the cached HTML (now ~1.5 ms, a memcpy). The offer stays per-request for its live price splice; the probe retry stays as a readiness backstop.
renderer — the render sidecar (finished-game image + public legal pages)
An internal Node service that runs shared ui/src/lib renderers server-side — bundled verbatim at
image build time (src/entry.ts → esbuild → dist/gameimage.mjs) so there is one renderer and no
drift from the browser. It serves two surfaces: the finished-game export PNG (on
skia-canvas, pixel-identical to the design the owner
signed off) and the public legal pages (the offer, the privacy policy and the EULA).
Interface
POST /render—{game, moves, alphabet, labels, dateLocale, hostname, scale?}→image/png.game/movesare the ui-model shapes (GameView/MoveRecord[]);alphabetis the per-variant(index, letter, value)table tile values are drawn from;labelslocalizes the non-play moves (pass/exchange/resign/timeout);hostname+dateLocalefeed the footer. Internal-only.GET /offer/— the public offer page astext/html: the owner-editedui/legal/offer_ru.md(baked into the image, read at boot) with the live catalog price list (§4.4) fetched as markdown from the backend's internal/api/v1/internal/offer/pricing(RENDERER_BACKEND_URL) and spliced in at the<#pricing_template#>marker, then rendered by the sharedui/src/lib/offer.tsrenderLegalHtml.GET /offer→ 301/offer/. Caddy routes/offer/here; a backend outage yields a 502, never a stale price list.GET /privacy/— the privacy policy, andGET /eula/the end-user licence agreement, both astext/html: the owner-editedui/legal/privacy_ru.md/ui/legal/eula_ru.md(baked in, read at boot), rendered once at boot by the same sharedrenderLegalHtmland served from cache. Static — no backend fetch.GET /privacy/GET /eula→ 301 to the trailing-slash form. Caddy routes these here too.GET /healthz— liveness (the compose healthcheck the backend'sdepends_ongates on).
The service renders and nothing else: for the PNG, authentication, the participant check and the
signed public download URL all live in the backend (backend/internal/server/export.go), the path
being client → gateway /dl/* → backend → this sidecar; for the offer, the catalog projection and
its cache live in the backend (backend/internal/payments/offer.go) and no user input reaches the
page.
Development
pnpm install # skia-canvas + esbuild MUST stay approved in pnpm-workspace.yaml
# (allowBuilds) or the native binary is silently never fetched
pnpm test # bundles, then node --test (PNG smoke + offer/legal render)
# local run on :8090 (RENDERER_PORT overrides). The server reads all three legal sources at boot, so
# point each at its ui/legal source (the baked paths do not exist in a local checkout); /offer/ also
# needs a reachable backend for the price fetch:
RENDERER_OFFER_MD=../ui/legal/offer_ru.md RENDERER_PRIVACY_MD=../ui/legal/privacy_ru.md \
RENDERER_EULA_MD=../ui/legal/eula_ru.md RENDERER_BACKEND_URL=http://localhost:8080 node src/server.mjs
The runtime image (renderer/Dockerfile, node:22-slim) bakes in Liberation Sans (the
UI font stack's Linux face) and Noto Color Emoji (the scoresheet 🏆); skia-canvas picks
both up through fontconfig. The fixture testdata/request.json is a real 35-move
self-played Russian Scrabble game.