DESIGN §31 — 0.2.6-dev

Part of DESIGN.md. Development after the 0.2.5 release.

31. Host bandwidth, layers 0 and 1

Unreleased. The maintainer's decision of 2026-10-12 on the bandwidth study (its measurements: a new player's first match costs the host about 52 MB, audio ≈ 40 % of it; returning players re-download after a re-extraction, a setup --force, a Docker rebuild or a changed tunnel address): do layer 0 (small fixes) and layer 1 (content-hashed URLs, long caching, brotli) first. Later layers (WebP / Opus variants, an asset-only service worker, a desktop client mode, importing an asset pack in the browser) are agreed and not part of this note. Nothing here touches the battle sim, the protocol messages or the committed data.

31.1 Layer 0 — small fixes

No BGM while the music is silent. Muted, or the BGM volume at 0, AudioManager.playBgm only remembers the wanted track (a different one still playing stops); setVolumes fetches and starts it once the music is audible again. SFX and voices were already gated. Normative line: design/client.md Audio.
WebSocket permessage-deflate (server/http/websocket.js WS_DEFLATE): frames from 1 KB, no server context takeover, a 2 KB server window, zlib memLevel 7 (about 72 KB of zlib state per connection). [ASSUMED] the parameters come from measured solo sessions (the server counters: 173 KB of frames → 60 KB on the wire; replaying 216 captured frames, windows above 2 KB gained nothing); co-op messages are the same kinds. A client that offers a narrower server window than 2 KB, which ws would refuse with a 400, connects uncompressed instead (narrowDeflateOffer). Normative line: design/network.md §8 Transport.
玩法说明 pages as WebP. tools/local-extract/extract.py writes a WebP copy beside each of the 19 local pages and the manifest lists it (GUIDE_WEBP_MODE); the guide preloads only the next page instead of both neighbours. The copies are lossy at quality 90: 25.6 MB → 4.2 MB on the CN client's pages (lossless would be 17.4 MB). Tutorial pages could go lossy only after a side-by-side comparison; the maintainer looked at 2× crops of four pages on 2026-10-12 and chose quality 90 (GUIDE_WEBP_MODE; extract.py --webp rewrites existing copies). Normative lines: design/client.md §13, ASSETS.md Post-processing.
Traffic counters. GET /healthz?traffic=1 adds traffic (HTTP body bytes and requests by category — assets, audio, code, data, other — and 304s; WebSocket wire bytes after compression and payload bytes before it) and assetHashes (the index state). The 问题反馈 diagnostics gain a traffic: line: the page's Resource Timing transferSize by the same categories (shared/assetPaths.js trafficCategory), other sites apart. Nothing is stored or uploaded. The maintainer's decision of 2026-10-12: only a loopback or private-network client gets the counters (server/http/routes.js, the address from net.js clientAddress, so TRUST_PROXY applies as for the WebSocket limits); any other client — also a visitor that a tunnel or proxy on this machine forwards — gets the plain report.
DEPLOY.md: a stable address keeps every player's cache, settings and reconnect token (a quick tunnel's new domain is a new site to the browser); HTTP/2 through the proxy saves round trips, not bytes; browsers offer brotli on HTTPS pages and localhost only; a Cloudflare cache rule for /assets/, /fonts/, /media/ (with the risk note).

31.2 Layer 1 — content-hashed URLs, long caching, brotli

Content-hash index (server/http/assetIndex.js): 1 s after the start, SHA-256 (16 hex) of every file under public/assets/ and public/fonts/ (dot names skipped, linked folders followed once), computed off the main thread, cached in .cache/asset-hashes.json by path + size + mtime (12,691 files / 724 MB here: 1.3 s the first time, 0.25 s after). A file whose size or mtime differs from its record is never vouched for; serving it asks for a rescan (at most one per 10 s). [ASSUMED] the 1 s delay and the 10 s rescan gap. A name that differs from a file's only in case finds that file (the manifest's /assets/module/wah-y.png is WAH-Y.png on this machine). SP_ASSET_INDEX=0 turns it off.
Served manifests (server/http/assetViews.js): /data/assets.json and /data/local-assets.json go out with every art URL carrying its file's hash as the first segment (/assets/~<hash>/…, /fonts/~<hash>/…; audio stays /assets/~<hash>/audio/….mp3). A Spine model — a { skel, atlas, textures } object of data/assets.json, a spine/… group of data/local-assets.json — carries one hash for all its files, since pixi-spine finds the atlas and the pages next to the skeleton. no-cache with the view's own ETag; rebuilt in memory when a manifest or the hashes change; the committed files are never written. Until the index is ready, without it, or on a static host: the files as committed.
The ~hash routes: static.js strips the segment for /assets/, /fonts/ and /media/; a hash that names the file's current bytes (its own or its model's) answers public, max-age=31536000, immutable, any other the current file with no-cache (an old page keeps working). Every indexed file's ETag is its content hash, on plain URLs too. Path segments, never ?v=: validSpine's /\.skel$/, SKILL_MODE_FILE's .mp3, pixi-spine's basename and folder resolution all need the URL to end in the file name.
Media: public/js/media.js turns /assets/~<hash>/audio/x.mp3 into /media/~<hash>/x; server/http/media.js resolves it like /media/x. The token death sound derived next to charDie drops charDie's hash (unhashedUrl).
Brotli (server/http/files.js): quality 5 on the fly with the same memory cache (one entry per file and encoding), for clients that name br at least as high as gzip; gzip for the rest (* alone never picks brotli [ASSUMED]); -br / -gz ETag suffixes. Measured against gzip-6 on this repository: .skel −27 %, data/*.json −26 %, vendor −14 %, public/js and server/sim −5 %, .atlas −7 %.

31.3 Measured sample session

Measured sample session (headless Chrome, a fresh profile, test/e2e/fastServer.mjs solo match from round 3 to the result after round 5, host bytes only, response headers included; the shop and the enemies vary between runs):

session	code	data	assets	audio	WebSocket (server → client)	host total
before, music on	3.16 MB	0.67 MB	9.0–9.7 MB	7.9 MB	163–179 KB (no compression)	20.8–21.4 MB
after, music on	2.95 MB	0.62 MB	9.5 MB	8.0 MB	60 KB on the wire (173 KB payload)	21.1 MB
before, muted	3.16 MB	0.67 MB	9.6 MB	7.3 MB (BGM)	165 KB	20.7 MB
after, muted	2.95 MB	0.62 MB	9.5 MB	0	57 KB on the wire	13.1 MB

A first visit with music on saves little (brotli on code and data, the WebSocket); a muted player saves the BGM. The caching gains are for returning players: within a day both versions answer from the browser cache, but after that the old version revalidated every asset of the session (≈ 340 requests here) and re-downloaded everything whose mtime had changed, while a hashed URL is never asked for again until its bytes change.

31.4 Open items and tests

Open: /fonts/fonts.css (linked by index.html) and the woff2 files it names keep plain URLs (content ETags only); the optional versioned vendor URLs (layer 1.5) are not done.

Tests: test/ui/audio.test.js (BGM gating; hashed audio through /media/~hash/), test/ws-compression.test.js, test/local-extract.test.js (guide WebP), test/ui/localArt.test.js (next-page preload), test/traffic.test.js, test/asset-paths.test.js, test/diag.test.js (traffic line), test/asset-index.test.js (index, views, ~hash routes), test/lobby.test.js (brotli negotiation, streamed brotli, content ETags), test/media-url.test.js, test/content/tokens_summons.test.js; the browser suites test/render/browser.test.js (Spine through hashed URLs, RENDER_E2E=1), test/ui/bond-audio.e2e.test.js (SP_E2E=1, the cue through /media/~hash/) and test/ui/real.e2e.test.js (SP_REAL_E2E=1: the co-op run loads Spine, audio and art through hashed URLs). The e2e servers wait for the asset index before the first page (test/e2e/client.mjs startRealServer, the in-process ones in their before), so the browser suites see the URLs a player sees. Golden: unchanged.

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