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google-labs-jules[bot]andPR0M3TH3AN
ee46b36a25
- Create `docs/webtorrent-architecture.md` detailing the "Webseeds are Peers" strategy. - Update `docs/video-availability-checks.md` with cross-reference. - Add "CRITICAL" warning comments to `js/webtorrent.js` and `js/gridHealth.js` to prevent regressions. - Enhance `tests/webtorrent-regression.test.mjs` to explicitly verify `urlList` passing in mocks. Co-authored-by: PR0M3TH3AN <[email protected]>
51 lines
3.3 KiB
Markdown
51 lines
3.3 KiB
Markdown
# WebTorrent Architecture & Strategy
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This document details the architecture of the WebTorrent implementation in bitvid, focusing on the client management, Service Worker integration, and the critical logic for handling webseeds.
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## Core Principle: Webseeds Are Peers
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**Crucial Logic (Regression Risk):**
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A recurring regression in this codebase involves treating "Webseeds" (HTTP sources) as distinct from "Peers" (P2P sources) in a way that marks webseed-only videos as "unhealthy".
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**The Correct Behavior:**
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* We **must** pass webseeds (`urlList`) directly to the WebTorrent client via `client.add(url, { urlList: [...] })`.
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* We **must** rely on the WebTorrent client to count that webseed as a connected peer.
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* **Health = Peers > 0**. If a webseed connects, `numPeers` becomes 1. This is "Healthy".
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**Anti-Pattern (Do Not Implement):**
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* *Do not* attempt to manually check if `peers === 0 && hasWebseed` and label it as a special "healthy" state in the UI logic.
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* *Do not* fail to pass `urlList` to `client.add`. If you don't pass it, WebTorrent won't see the peer, `numPeers` stays 0, and the video is marked unhealthy.
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## Architecture Components
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### 1. The Singleton Client (`TorrentClient`)
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`js/webtorrent.js` exports a singleton `torrentClient`. We do not instantiate multiple clients.
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* **Reason:** WebTorrent clients are expensive. They open many socket connections and maintain DHT state.
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* **Reuse:** The same client instance is used for both "Probing" (checking health) and "Streaming" (playback).
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### 2. The Service Worker (`sw.min.js`)
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Browser-based WebTorrent cannot write directly to the filesystem or stream directly to a `<video>` tag's `src` attribute efficiently.
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* **Solution:** We register a Service Worker that acts as a proxy.
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* **Flow:** `<video src="/webtorrent/...">` -> Browser Network Request -> Service Worker Intercept -> Fetch bytes from `TorrentClient` -> Return stream.
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### 3. The "Claim" Dance (Critical Startup Logic)
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A major source of "grey screen" bugs (video loading forever) occurs when the Service Worker is installed but **not controlling the page**.
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* **Scenario:** User loads page -> SW installs -> User plays video. If the SW hasn't "claimed" the client, the network request bypasses the SW and fails (404).
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* **Fix:** `TorrentClient.init()` explicitly waits for `navigator.serviceWorker.controller` to exist. It calls `clients.claim()` in the SW and waits for the `controllerchange` event.
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## Probing Strategy (`probePeers`)
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We probe videos before playing them to determine if they are available.
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1. **Input:** Magnet URI + optional Webseed URL.
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2. **Action:** Call `client.add` with `urlList` set to the webseed.
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3. **Wait:** Wait for `torrent.on('wire')` (connection established) or `peers > 0`.
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4. **Result:**
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* **Healthy:** `peers > 0`. (Includes webseeds!)
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* **Unhealthy:** Timeout with `peers === 0`.
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## Browser Specifics
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* **Brave:** Requires aggressive Service Worker cleanup (`unregister` all) on startup due to lingering stale workers preventing new registrations.
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* **Firefox:** Uses a specific `highWaterMark` tuning and separate handler (`handleFirefoxTorrent`) to manage memory buffering differences.
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* **Chrome/Chromium:** Standard path (`handleChromeTorrent`), but includes logic to strip specific trackers/webseeds that trigger CORS warnings (e.g., specific demo trackers).
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