92 lines
3.3 KiB
Markdown
92 lines
3.3 KiB
Markdown
---
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id: 004-coalesce-stream-resolves-a92d40
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title: Coalesce concurrent resolveStreams calls for the same video
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created: 2026-09-29
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depends_on: [001-perf-timing-marks-105acc]
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est_files: 1
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---
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# 004 — Coalesce concurrent resolveStreams calls
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## Objective
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`resolveStreams(videoId)` checks `streamCache` but has no in-flight map, so two
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requests for the same id that arrive before the first finishes (a warm-up + the
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real play, two devices, the media cache's `getInfo` + `/api/streams`) each spawn a
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~6 s `yt-dlp -J`. After this plan, concurrent callers share ONE promise; a failure
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is not cached (the next call retries).
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## Context the executor must NOT rediscover
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`server/server.js:457-494`:
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```js
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async function resolveStreams(videoId) {
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const now = Date.now();
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const cached = streamCache.get(videoId);
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if (cached && now < cached.expiresAt) return cached;
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const out = await runYtdlpResilient(['-J', '--no-warnings', `https://www.youtube.com/watch?v=${videoId}`]);
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const info = JSON.parse(out);
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...
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streamCache.set(videoId, entry);
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return entry;
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}
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```
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`streamCache` and `STREAM_CACHE_MAX` are declared just above it.
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## Steps
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1. `server/server.js` — rename the existing function `resolveStreams` to
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`resolveStreamsUncached` (definition only; body unchanged).
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2. Directly after that function add:
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```js
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// One yt-dlp -J per video at a time: concurrent callers (warm-up + play,
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// two devices, the media cache's getInfo) share the in-flight promise.
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const inflightStreams = new Map(); // videoId -> Promise<entry>
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function resolveStreams(videoId) {
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const cached = streamCache.get(videoId);
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if (cached && Date.now() < cached.expiresAt) return Promise.resolve(cached);
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let p = inflightStreams.get(videoId);
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if (!p) {
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p = resolveStreamsUncached(videoId).finally(() => inflightStreams.delete(videoId));
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inflightStreams.set(videoId, p);
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}
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return p;
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}
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```
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All existing callers keep calling `resolveStreams` (it still returns a Promise).
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3. Create `server/streams-inflight.test.js`? — NO. Keep it in-file; instead verify with the
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script below.
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## Out of scope / do NOT touch
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- Cache TTL logic, `runYtdlpResilient`, format filtering.
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## Verification
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```bash
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cd /home/user/ytplayer/server && grep -n "function resolveStreams\|function resolveStreamsUncached\|inflightStreams" server.js
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bun build server.js --target=bun --outdir=/tmp/ytp-check >/dev/null && echo SERVER_OK
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bun run test 2>&1 | grep -E "^ *[0-9]+ (pass|fail)"
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```
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Expected: both functions + map present, `SERVER_OK`, all server test files `0 fail`.
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## Report format (executor: follow exactly)
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Output ONLY the following, no other prose:
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1. `git diff` (unified) of all changes.
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2. Raw output of the Verification commands.
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3. `Findings:` — max 10 lines.
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Do not commit. Do not push. Do not touch files outside the Steps.
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## Execution log
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- Executor: in-session Agent (haiku). Attempts: 1. Fix rounds: 0.
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- Orchestrator re-ran Verification: both functions and `inflightStreams` present, `bun build` ok, `bun run test` all 5 server files 0 fail (media-cache 23 pass is the original baseline).
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- Executor Findings (verbatim): Plan executed successfully. Both renamed function and wrapper present in correct location. In-flight map correctly coalesces concurrent calls. All 58 server tests pass. Build completes with no errors. No deviations from plan requirements.
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