Files
music/sidecar/stream-audio.ts
T
officer 2a70bc18d7 three bottlenecks in streaming and loading
Measured, not guessed.

ffprobe is gone from the stream path. It ran on the first request for each
file — 50ms warm, 315ms cold on this machine, paid before the first byte, once
per file per sidecar restart — to fill X-Audio-Duration, a header nothing in
the web read and which duplicates the durationSec the indexer already wrote
into meta.json. Removed rather than cached harder: the fastest work is the work
not done, and a second copy of a number is a second thing that can disagree.
BREAKING for any client that read that header; read /meta instead, which every
client already fetches to build its queue.

/stream gains an ETag and Cache-Control. It was the only route with no
validator at all — cover, meta, lyrics and poster have had one all along — so
every seek and every replay re-read the file over the network. mtime+size
identifies the bytes, since a re-encode replaces the file. A Range request
never answers 304: that would answer a question about part of a file with a
statement about all of it, and players handle it badly.

And `?v=` makes covers cacheable rather than merely revalidatable. `no-cache`
means "ask before reusing", so a grid of forty albums cost forty conditional
requests on every load, all answering 304. The manifest already carries each
album's version, so passing it costs the client nothing — and the server then
answers `immutable`, making a repeat visit send nothing at all.

That last one is deliberately conditional on `v` being present, which keeps it
backward compatible: a client that has not been updated gets today's behaviour
and cannot end up holding a stale cover forever.
2026-08-19 15:15:35 +00:00

106 lines
4.1 KiB
TypeScript

import { stat } from 'node:fs/promises';
import { resolve, sep } from 'node:path';
import { homedir } from 'node:os';
// All processing lives here (the platform is just a proxy). Files live under the owner's home — single
// super user, so HOME_DIR. Paths from the app are home-relative (e.g. "Music/Artist/Album/track.mp3"),
// exactly like file-browser /raw.
const ROOT_DIR = homedir();
const CONTENT_TYPES: Record<string, string> = {
mp3: 'audio/mpeg',
m4a: 'audio/mp4',
mp4: 'audio/mp4',
aac: 'audio/aac',
flac: 'audio/flac',
wav: 'audio/wav',
ogg: 'audio/ogg',
opus: 'audio/opus',
wma: 'audio/x-ms-wma',
};
// NO ffprobe HERE, and no `X-Audio-Duration`.
//
// This used to shell out to ffprobe on the first request for each file — measured at 50ms warm and 315ms
// cold, paid before the first byte, once per file per sidecar restart. It filled a header that nothing in
// the web read, duplicating `durationSec` which the indexer already wrote into the album's `meta.json`
// and which every client fetches anyway to build its queue.
//
// Removed rather than cached harder: the fastest work is the work not done, and a second copy of a number
// is a second thing that can disagree.
/** Resolve a home-relative path within ROOT_DIR; null if it escapes (traversal). */
function resolveWithinRoot(relPath: string): string | null {
const clean = relPath.replace(/^\/+/, '');
const abs = resolve(ROOT_DIR, clean);
if (abs !== ROOT_DIR && !abs.startsWith(ROOT_DIR + sep)) return null;
return abs;
}
/** Serve an audio file with byte-range support and an mtime+size ETag. */
export async function streamAudioFile(
relPath: string,
rangeHeader: string | null,
ifNoneMatch: string | null = null,
): Promise<Response> {
const absPath = resolveWithinRoot(relPath);
if (!absPath) return new Response('Invalid path', { status: 400 });
let s;
try {
s = await stat(absPath);
} catch {
return new Response('Not found', { status: 404 });
}
if (!s.isFile()) return new Response('Not a file', { status: 404 });
const total = s.size;
const ext = absPath.slice(absPath.lastIndexOf('.') + 1).toLowerCase();
const contentType = CONTENT_TYPES[ext] ?? 'application/octet-stream';
const file = Bun.file(absPath);
// An audio file's bytes do not change; a re-encode replaces the file, which moves mtime and size. So
// the pair identifies the content, and a client that has played this track once can seek in it without
// fetching anything again.
//
// This was the ONLY route with no validator at all — cover, meta, lyrics and poster have had one all
// along — so every seek and every replay re-read the file over the network.
const etag = `"${s.mtimeMs.toString(36)}-${total.toString(36)}"`;
const baseHeaders: Record<string, string> = {
'Content-Type': contentType,
'Accept-Ranges': 'bytes',
ETag: etag,
// `no-cache` means "you may keep it, but ask first" — a conditional request rather than a blind
// refetch. `private` because a member's library is not a proxy's to hold.
'Cache-Control': 'private, no-cache',
};
// Whole-file revalidation. Deliberately NOT applied to a Range request: a 304 there would answer a
// question about part of a file with a statement about all of it, and players handle that badly.
if (!rangeHeader && ifNoneMatch === etag) {
return new Response(null, { status: 304, headers: baseHeaders });
}
if (rangeHeader) {
const m = rangeHeader.match(/bytes=(\d*)-(\d*)/);
if (m) {
const start = m[1] ? parseInt(m[1], 10) : 0;
const end = m[2] ? parseInt(m[2], 10) : total - 1;
if (Number.isNaN(start) || start < 0 || end >= total || start > end) {
return new Response('Invalid range', { status: 416, headers: { 'Content-Range': `bytes */${total}` } });
}
return new Response(file.slice(start, end + 1), {
status: 206,
headers: {
...baseHeaders,
'Content-Range': `bytes ${start}-${end}/${total}`,
'Content-Length': String(end - start + 1),
},
});
}
}
return new Response(file, { status: 200, headers: { ...baseHeaders, 'Content-Length': String(total) } });
}