Serialize saves, disable idle timeout, cap savable length at 3h

server/server.js

@@ -47,7 +47,17 @@ const FFMPEG      = process.env.FFMPEG_PATH || 'ffmpeg';
 // whole downlink (~7.6 MB/s measured), and since /api/play fetches its own
 // googlevideo slices over the same link, one long save starved every
 // concurrent playback (stalled at ~27 s, 11 KB/s). Leave headroom.
-const DOWNLOAD_RATE = process.env.DOWNLOAD_RATE || '3M';
+const DOWNLOAD_RATE = process.env.DOWNLOAD_RATE || '2M';
+
+// Saves run ONE AT A TIME. Two concurrent rate-capped saves plus playback
+// still filled the homelab's ~7.5 MB/s downlink and playback starved, so
+// additional saves wait their turn (the client just sees a longer save).
+let saveChain = Promise.resolve();
+function withSaveSlot(fn) {
+  const run = saveChain.then(fn, fn);
+  saveChain = run.catch(() => {});
+  return run;
+}
 
 // ----------------------------------------------------------------------------
 // BUILD_TAG — must be DETERMINISTIC across restarts of identical code.
@@ -682,7 +692,7 @@ app.get('/api/play', async (c) => {
 // didn't match the extraction client.
 // Live streams have no end: yt-dlp/ffmpeg would pull the HLS manifest forever
 // (one such "save" ran for an hour and ate 14 GB). Refuse them up front.
-const MAX_SAVE_SECONDS = Number(process.env.MAX_SAVE_SECONDS || 4 * 3600);
+const MAX_SAVE_SECONDS = Number(process.env.MAX_SAVE_SECONDS || 3 * 3600);
 async function assertNotLive(videoId) {
   const { info } = await resolveStreams(videoId);
   if (info.is_live || info.live_status === 'is_live' || info.live_status === 'post_live') {
@@ -707,13 +717,16 @@ async function ytdlpDownloadResponse(videoId, fp, formatArgs, signal) {
     const tmp = `${tmpdir()}/${tmpBase}.mp4`;
     const ctl = new AbortController();
     entry = { waiters: 0, tmpBase, ctl };
-    entry.promise = runYtdlp([
-      `https://www.youtube.com/watch?v=${videoId}`,
-      '--no-warnings', '--no-playlist',
-      ...formatArgs,
-      '--limit-rate', DOWNLOAD_RATE,
-      '-o', tmp,
-    ], { signal: ctl.signal }).then(() => ({ tmp, size: statSync(tmp).size }));
+    entry.promise = withSaveSlot(() => {
+      if (ctl.signal.aborted) throw new Error('save cancelled');
+      return runYtdlp([
+        `https://www.youtube.com/watch?v=${videoId}`,
+        '--no-warnings', '--no-playlist',
+        ...formatArgs,
+        '--limit-rate', DOWNLOAD_RATE,
+        '-o', tmp,
+      ], { signal: ctl.signal });
+    }).then(() => ({ tmp, size: statSync(tmp).size }));
     inflightDownloads.set(key, entry);
   }
   entry.waiters++;
@@ -776,14 +789,14 @@ async function ytdlpEditedDownloadResponse(videoId, fp, keep, signal) {
   let size, fd;
   try {
     // 1) Grab the full source (video+audio merged) so ffmpeg has both streams.
-    await runYtdlp([
+    await withSaveSlot(() => runYtdlp([
       `https://www.youtube.com/watch?v=${videoId}`,
       '--no-warnings', '--no-playlist',
       '-f', 'bv*[height<=720][ext=mp4]+ba[ext=m4a]/bv*[height<=720]+ba/b[ext=mp4]/b',
       '--merge-output-format', 'mp4',
       '--limit-rate', DOWNLOAD_RATE,
       '-o', srcTmp,
-    ], { signal });
+    ], { signal }));
     // 2) Trim + concat the keep segments into the final custom video.
     await runFfmpeg([
       '-y', '-hide_banner', '-loglevel', 'error',
@@ -1223,9 +1236,12 @@ async function main() {
     port: PORT,
     fetch: app.fetch,
     // Default is 10s, which killed /api/download proxy streams whenever the
-    // connection went idle mid-transfer. 240s covers slow saves; Bun caps
-    // this field at 255.
-    idleTimeout: 240,
+    // connection went idle mid-transfer. 240s then killed every save whose
+    // server-side yt-dlp phase (no bytes sent yet) ran longer than 4 min —
+    // long videos at the rate cap — and the client retried in a loop.
+    // 0 disables the idle timeout entirely (verified with a 300s request);
+    // runaway downloads are bounded by MAX_SAVE_SECONDS + kill-on-disconnect.
+    idleTimeout: 0,
   });
 
   console.log(`[ytplayer] Listening → http://localhost:${PORT}`);