Sessions leave redacted logs; viewers wait for a member relay's source before opening it

Logs: one redaction pass (query strings to names, member tokens,
passwords, cookies, auth headers) for every line; daily files with size
and age caps in the app (hosted server included) and the dedicated
server (--log-dir); swaps, relay channels, per-member /r /m /j outcomes,
server fetches, mpv load errors, yt-dlp runs. Settings > About: Copy
diagnostics, Open logs folder.

Bilibili through someone else: the viewer opened /r/ before the source
dialled in; the server holds that request and mpv gives up after 5 s
("could not be opened"). Viewers now open a member relay once it is
live, the putter starts its source before its own player, and track
sizes are read in parallel.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/server/bin/server.dart

@@ -30,6 +30,9 @@ Future<void> main(List<String> args) async {
         help: 'cookies.txt or browser-extension JSON export to log that yt-dlp in (sites that refuse guests). '
             'An account login: keep it private. Copied into --yt-dlp-dir at start.')
     ..addOption('config', help: 'YAML or JSON config file (keys as in AppConfig); overrides the other flags.')
+    ..addOption('log-dir',
+        help: 'Folder for the rotating log files (server-YYYY-MM-DD.log, kept 7 days). '
+            'Default: logs next to --config, else logs next to this binary (systemd: \$STATE_DIRECTORY/logs).')
     ..addFlag('upgrade',
         negatable: false,
         help: 'Update this install (the whole folder, app included) to the latest release, then exit. '
@@ -58,8 +61,14 @@ Future<void> main(List<String> args) async {
   }
 
   initLogging(level: pkg_logging.Level.INFO);
-  AppConfig config;
   final configPath = parsed['config'] as String?;
+  final logDir = (parsed['log-dir'] as String?) ??
+      (configPath != null ? '${File(configPath).absolute.parent.path}${Platform.pathSeparator}logs' : serverDataDir('logs'));
+  final files = startLogFiles(logDir, prefix: 'server');
+  if (files != null) stdout.writeln('logs: ${files.dir}');
+  pkg_logging.Logger('server').info('watch-together-server $appVersion (proto ${RelayConstants.protoVersion}) '
+      'on ${Platform.operatingSystem} ${Platform.operatingSystemVersion}, pid $pid');
+  AppConfig config;
   try {
     if (configPath != null) {
       config = await AppConfig.loadFile(configPath);
@@ -114,6 +123,7 @@ Future<void> main(List<String> args) async {
     if (msg is! Map) continue;
     if (msg['t'] == 'error') {
       stderr.writeln('server failed to start: ${msg['message']}');
+      pkg_logging.Logger('server').severe('failed to start: ${msg['message']}');
       exitCode = 1;
       break;
     }

packages/server/lib/src/jellyfin_relay.dart

@@ -80,15 +80,16 @@ void mountJellyfinRelayRoute(
       upRes = await upReq.close().timeout(timeout);
     } catch (e) {
       _relayLog.warning('upstream ${ref.itemId}: $e');
+      onLog?.call(token, MediaLog(method: req.method.name, path: '/j/$sid/$itemId', rangeHeader: range,
+          status: 502, bytesWritten: 0, durationMs: stopwatch.elapsedMilliseconds));
       return _plain(502);
     }
 
-    final shortToken = token.length > 4 ? '…${token.substring(token.length - 4)}' : token;
     void log(int status, int bytes) => onLog?.call(
         token,
         MediaLog(
           method: req.method.name,
-          path: '/j/$sid/$shortToken/$itemId',
+          path: '/j/$sid/$itemId',
           rangeHeader: range,
           status: status,
           bytesWritten: bytes,

packages/server/lib/src/media_endpoint.dart

@@ -27,6 +27,24 @@ class MediaLog {
       '$method $path range=${rangeHeader ?? '-'} -> $status bytes=$bytesWritten ${durationMs}ms';
 }
 
+final _requestLog = createLogger('media');
+
+/// Each member's media requests (`/m`, `/r`, `/j`) for the log: a few per
+/// member, route and outcome every 30 s (mpv reads in many ranges), every
+/// failure kind at least once per window.
+class MediaRequestLog {
+  final _throttle = LogThrottle(burst: 4, window: const Duration(seconds: 30));
+
+  void call(String who, MediaLog log) {
+    final bad = log.status >= 400;
+    final route = log.path.split('/').where((s) => s.isNotEmpty).firstOrNull ?? '';
+    final pass = _throttle.allow('$who $route ${bad ? log.status : 'ok'}');
+    if (pass == null) return;
+    final line = '$pass$who: $log';
+    bad ? _requestLog.warning(line) : _requestLog.info(line);
+  }
+}
+
 class MediaResolution {
   final int status;
   final Map<String, String> headers;
@@ -187,14 +205,20 @@ void mountSessionMediaRoute(
     }
     final res = resolveMediaRequest(rangeHeader: rangeHeader, size: size, filename: media.name);
     if (res.status != 200 && res.status != 206) {
+      onLog?.call(token, MediaLog(
+          method: req.method.name,
+          path: '/m/$sid/${media.name}',
+          rangeHeader: rangeHeader,
+          status: res.status,
+          bytesWritten: 0,
+          durationMs: stopwatch.elapsedMilliseconds));
       return _gatedResponse(res);
     }
     final end = res.end ?? size - 1;
     final byteCount = end - res.start + 1;
-    final shortToken = token.length > 4 ? '…${token.substring(token.length - 4)}' : token;
     onLog?.call(token, MediaLog(
       method: req.method.name,
-      path: '/m/$sid/$shortToken/${media.name}',
+      path: '/m/$sid/${media.name}',
       rangeHeader: rangeHeader,
       status: res.status,
       bytesWritten: byteCount,

packages/server/lib/src/queue_ops.dart

@@ -6,6 +6,8 @@ import 'server_hub.dart';
 // `queue` messages (Up next, see PROTOCOL.md "Queue"): what an added item
 // may carry, and the ops applied to the engine's queue.
 
+final _log = createLogger('queue');
+
 final _key = RegExp(r'^[A-Za-z0-9_-]{8,64}$');
 
 bool _httpUrl(String? url) {
@@ -76,9 +78,11 @@ void handleQueueIntent(ServerHub hub, String token, RelicWebSocket ws, Map<Strin
       final error = engine.applyQueueAdd(token, cleaned.item,
           next: intent.next, privateUrl: cleaned.privateUrl, thumb: thumb);
       if (error != null) {
+        _log.info('${hub.who(token)}: add "${cleaned.item.title}" (${cleaned.item.how.name}) refused: $error');
         wsErr(ws, error);
         return;
       }
+      _log.info('${hub.who(token)}: add "${cleaned.item.title}" (${cleaned.item.how.name}${intent.next ? ', next' : ''})');
       changed = true;
     case 'move':
       changed = engine.applyQueueMove(token, intent.id, intent.to);
@@ -89,5 +93,9 @@ void handleQueueIntent(ServerHub hub, String token, RelicWebSocket ws, Map<Strin
     case 'skip':
       changed = engine.applyQueuePlay(token, '');
   }
+  if (intent.op != 'add') {
+    _log.info('${hub.who(token)}: ${intent.op}${intent.id.isEmpty ? '' : ' ${intent.id}'}'
+        '${intent.op == 'move' ? ' to ${intent.to}' : ''}${changed ? '' : ' (no change)'}');
+  }
   if (changed) hub.changed();
 }

packages/server/lib/src/relay_routes.dart

@@ -203,7 +203,9 @@ class ActiveRelay {
     final r = ActiveRelay._(mediaId, name, null, onLiveChanged, fetch: true, queueId: queueId, warm: queueId != null)
       ..onFail = onFail;
     final media = r._media = LinkRelayMedia(url, ytDlp: ytDlp);
+    _log.info('relay fetch of "$name"${queueId == null ? '' : ' (warm, Up next $queueId)'}: ${logUrl(url)}');
     unawaited(() async {
+      final sw = Stopwatch()..start();
       try {
         final tracks = await media.open();
         final infos = <_TrackInfo>[
@@ -213,12 +215,14 @@ class ActiveRelay {
                 : (kind: t.kind, size: await t.bytes!.size(), pieces: null),
         ];
         if (r._disposed) return;
+        _log.info('relay fetch of "$name" ready in ${sw.elapsedMilliseconds} ms: '
+            '${infos.map((t) => t.size != null ? '${t.kind.isEmpty ? 'file' : t.kind} ${t.size} bytes' : '${t.kind} ${t.pieces!.length} pieces').join(' + ')}');
         r._setTracks(relayTrackSpecs(tracks));
         r._local = [for (var i = 0; i < tracks.length; i++) LocalRelayFeed(tracks[i], r.buffers[i])];
         r._attachAll(r._local, infos);
         onLiveChanged();
       } catch (e) {
-        _log.warning('relay fetch: cannot read the link: $e');
+        _log.warning('relay fetch of "$name": cannot read the link after ${sw.elapsedMilliseconds} ms: $e');
         if (!r._disposed) {
           r.failed = true;
           r.onFail?.call('$e');
@@ -370,9 +374,12 @@ void mountRelayRoutes(
     return WebSocketUpgrade((final ws) async {
       final r = found;
       if (r == null) {
+        _log.warning('relay channel refused: not the source of ${queueId == null ? 'the current media' : 'Up next item $queueId'}');
         await _closeNotSource(ws);
         return;
       }
+      final opened = DateTime.now();
+      String? closed;
       ws.pingInterval = Duration(seconds: RelayConstants.pingIntervalSecs);
       var attached = false;
       try {
@@ -397,7 +404,7 @@ void mountRelayRoutes(
                   return;
                 }
                 attached = true;
-                _log.info('relay channel up (${r.name}, '
+                _log.info('relay channel up (${r.name}${r.warm ? ', warm' : ''}, from ${r.sourceId}, '
                     '${infos.map((t) => t.size != null ? '${t.size} bytes' : '${t.pieces!.length} pieces').join(' + ')})');
                 r._attachChannel(ws, infos);
               case 'end':
@@ -413,6 +420,8 @@ void mountRelayRoutes(
                   }
                 }
             }
+          } else if (e is CloseReceived) {
+            closed = '${e.code ?? '-'} ${e.reason}'.trim();
           } else if (e is BinaryDataReceived && attached) {
             try {
               // Pull ids are unique across tracks: only the owner takes it.
@@ -423,11 +432,13 @@ void mountRelayRoutes(
             } catch (_) {}
           }
         }
-      } catch (_) {
-        // channel broke
+      } catch (e) {
+        _log.warning('relay channel broke (${r.name}): $e');
       } finally {
         r._detachChannel(ws);
-        _log.info('relay channel down (${r.name})');
+        _log.info('relay channel down (${r.name}, from ${r.sourceId}) after '
+            '${DateTime.now().difference(opened).inSeconds} s, ${closed == null ? 'no close frame' : 'closed $closed'}'
+            '${r._disposed ? ', relay dropped' : ''}');
       }
     });
   });
@@ -438,83 +449,97 @@ void mountRelayRoutes(
     final token = req.pathParameters.raw[#token] ?? '';
     final key = req.pathParameters.raw[#mediaId] ?? '';
     final track = tracked ? int.tryParse(req.pathParameters.raw[#seg] ?? '') ?? -1 : null;
-    final session = sessions.get(sid);
-    if (session == null) return _plain(410);
-    switch (session.gate(token)) {
-      case MediaGate.ok:
-        break;
-      default:
-        return _plain(401);
-    }
-    // A player still on an older media must not get the new one's bytes.
-    final r = relayAt(key);
-    if (r == null) return _plain(404);
-    final notConnected = Response(503,
-        body: Body.fromString('relay source not connected'),
-        headers: Headers.build((h) => h['retry-after'] = ['2']));
-    if (!await r.whenKnown()) return notConnected;
-    final buffer = r.bufferAt(track);
-    if (buffer == null || (piece && buffer is! PieceBuffer)) return _plain(404);
-    if (!await buffer.ready()) return notConnected;
+    final pieceIndex = piece ? req.pathParameters.raw[#piece] ?? '' : null;
     final typed = req.headers.range;
     String? rangeHeader;
     if (typed != null && typed.ranges.isNotEmpty) {
       final x = typed.ranges.first;
       rangeHeader = '${typed.unit}=${x.start?.toString() ?? ''}-${x.end?.toString() ?? ''}';
     }
+    // Every outcome goes to the log (throttled per member there); a 503
+    // after a long wait is a source that never came up.
+    Response logged(Response res, {int bytes = 0}) {
+      onLog?.call(
+          token,
+          MediaLog(
+            method: req.method.name,
+            path: '/r/$sid/$key/${track == null ? '' : '$track/'}${pieceIndex == null ? '' : 'p/$pieceIndex'}',
+            rangeHeader: rangeHeader,
+            status: res.statusCode,
+            bytesWritten: bytes,
+            durationMs: stopwatch.elapsedMilliseconds,
+          ));
+      return res;
+    }
+
+    final session = sessions.get(sid);
+    if (session == null) return logged(_plain(410));
+    switch (session.gate(token)) {
+      case MediaGate.ok:
+        break;
+      default:
+        return logged(_plain(401));
+    }
+    // A player still on an older media must not get the new one's bytes.
+    final r = relayAt(key);
+    if (r == null) return logged(_plain(404));
+    Response notConnected() => logged(Response(503,
+        body: Body.fromString('relay source not connected'),
+        headers: Headers.build((h) => h['retry-after'] = ['2'])));
+    if (!await r.whenKnown()) return notConnected();
+    final buffer = r.bufferAt(track);
+    if (buffer == null || (piece && buffer is! PieceBuffer)) return logged(_plain(404));
+    if (!await buffer.ready()) return notConnected();
     if (buffer is PieceBuffer) {
       if (!piece) {
         buffer.opened(token);
-        return Response(200,
+        return logged(Response(200,
             body: Body.fromString(buffer.playlist ?? '', mimeType: MimeType('application', 'vnd.apple.mpegurl')),
-            headers: Headers.build((h) => h['cache-control'] = ['no-store']));
+            headers: Headers.build((h) => h['cache-control'] = ['no-store'])));
       }
-      final index = int.tryParse(req.pathParameters.raw[#piece] ?? '');
-      if (index == null || index < 0 || index >= buffer.list!.length) return _plain(404);
+      final index = int.tryParse(pieceIndex ?? '');
+      if (index == null || index < 0 || index >= buffer.list!.length) return logged(_plain(404));
       final data = await buffer.piece(token, index);
-      if (data == null) return notConnected;
+      if (data == null) return notConnected();
       final res = resolveMediaRequest(rangeHeader: rangeHeader, size: data.length, filename: 'piece');
       final headers = Headers.build((h) => res.headers.forEach((k, v) => h[k] = [v]));
       if (res.status != 200 && res.status != 206) {
-        return Response(res.status, body: Body.fromString('status ${res.status}'), headers: headers);
+        return logged(Response(res.status, body: Body.fromString('status ${res.status}'), headers: headers));
       }
       final end = res.end ?? data.length - 1;
       final n = end - res.start + 1;
       buffer.bytesToViewers += n;
       session.addBytes(token, n);
-      return Response(res.status,
-          body: Body.fromData(Uint8List.sublistView(data, res.start, end + 1), mimeType: MimeType.octetStream),
-          headers: headers);
+      return logged(
+          Response(res.status,
+              body: Body.fromData(Uint8List.sublistView(data, res.start, end + 1), mimeType: MimeType.octetStream),
+              headers: headers),
+          bytes: n);
     }
     final size = (buffer as RelayBuffer).size;
     final res = resolveMediaRequest(rangeHeader: rangeHeader, size: size, filename: r.name);
     final headers = Headers.build((h) => res.headers.forEach((k, v) => h[k] = [v]));
     if (res.status != 200 && res.status != 206) {
-      return Response(res.status, body: Body.fromString('status ${res.status}'), headers: headers);
+      return logged(Response(res.status, body: Body.fromString('status ${res.status}'), headers: headers));
     }
     final end = res.end ?? size - 1;
-    final shortToken = token.length > 4 ? '…${token.substring(token.length - 4)}' : token;
-    onLog?.call(
-        token,
-        MediaLog(
-          method: req.method.name,
-          path: '/r/$sid/$shortToken/$key/${track == null ? '' : '$track/'}${r.name}',
-          rangeHeader: rangeHeader,
-          status: res.status,
-          bytesWritten: end - res.start + 1,
-          durationMs: stopwatch.elapsedMilliseconds,
-        ));
-    final Stream<Uint8List> body =
-        buffer.read(token, res.start, end, onSent: (n) => session.addBytes(token, n));
+    final Stream<Uint8List> body = buffer
+        .read(token, res.start, end, onSent: (n) => session.addBytes(token, n))
+        .transform(StreamTransformer.fromHandlers(handleError: (e, st, sink) {
+      _readFails(token, '${r.name} track ${track ?? 0} from ${res.start}: $e');
+      sink.addError(e, st);
+    }));
     MimeType mime;
     try {
       mime = MimeType.parse(res.headers['content-type'] ?? '');
     } catch (_) {
       mime = MimeType.octetStream;
     }
-    return Response(res.status,
-        body: Body.fromDataStream(body, mimeType: mime, contentLength: end - res.start + 1),
-        headers: headers);
+    return logged(
+        Response(res.status,
+            body: Body.fromDataStream(body, mimeType: mime, contentLength: end - res.start + 1),
+            headers: headers),
+        bytes: end - res.start + 1);
     }
 
   // `:seg` is the name of a single file, the track of several (the router
@@ -525,3 +550,11 @@ void mountRelayRoutes(
 }
 
 Response _plain(int status) => Response(status, body: Body.fromString('status $status'));
+
+final _readFailThrottle = LogThrottle(burst: 3);
+
+/// A viewer's read of a relay broke (the source never sent the bytes).
+void _readFails(String token, String what) {
+  final pass = _readFailThrottle.allow(token);
+  if (pass != null) _log.warning('${pass}relay read for a viewer broke: $what');
+}

packages/server/lib/src/serve.dart

@@ -12,7 +12,7 @@ import 'sync_server.dart';
 ///
 /// On [events] it reports `{'t':'ready','port':p,'stop':SendPort}` or
 /// `{'t':'error','message':m}`, and forwards log records as
-/// `{'t':'log','level','logger','message'[,'error']}`. Sending
+/// `{'t':'log','level','logger','message'[,'error'][,'stack']}`. Sending
 /// `{'t':'stop'}` to the `stop` port stops the server; the returned future
 /// completes once it is down. `{'t':'file','path':p,'reply':SendPort}` makes
 /// a file on this machine the hosted file (the hosting app's in-session file
@@ -29,6 +29,7 @@ Future<void> serve(Map<String, Object?> config, {SendPort? events}) async {
           'logger': r.loggerName,
           'message': r.message,
           if (r.error != null) 'error': '${r.error}',
+          if (r.stackTrace != null) 'stack': '${r.stackTrace}',
         }));
   }
   final SyncServer server;

packages/server/lib/src/server_hub.dart

@@ -70,17 +70,32 @@ class ServerHub {
   /// Replaces the relay (null: the new media is not relayed). The old
   /// buffer is dropped with it.
   void setRelay(ActiveRelay? next) {
-    if (!identical(relay, next)) relay?.dispose();
+    if (!identical(relay, next)) {
+      final old = relay;
+      if (old != null) _hubLog.info('relay of "${old.name}" dropped (sent ${_sent(old)})');
+      old?.dispose();
+    }
     relay = next;
   }
 
+  static String _sent(ActiveRelay r) =>
+      '${(r.buffers.fold<int>(0, (a, b) => a + b.bytesFromFeed) / 1048576).toStringAsFixed(1)} MiB in';
+
   /// The warm relay: Up next's first item relayed before it goes up, so
   /// every viewer preloads it (see ARCHITECTURE "Getting ready"); null
   /// when that item is not relayed (or nobody would read it).
   ActiveRelay? warm;
 
   void _setWarm(ActiveRelay? next) {
-    if (!identical(warm, next)) warm?.dispose();
+    if (!identical(warm, next)) {
+      final old = warm;
+      if (old != null) _hubLog.info('warm relay of Up next ${old.queueId} ("${old.name}") dropped (${_sent(old)})');
+      old?.dispose();
+      if (next != null) {
+        _hubLog.info('warm relay of Up next ${next.queueId} ("${next.name}"): '
+            '${next.fetch ? 'the server fetches it' : next.sourceId.isEmpty ? 'from the first member with an account' : 'from ${next.sourceId}'}');
+      }
+    }
     warm = next;
   }
 
@@ -214,9 +229,11 @@ class ServerHub {
         ? w.fetch && !w.failed
         : !w.fetch && w.sourceToken == token && (!w.known || _sameTracks(w.tracks, tracks));
     if (ok) {
+      _hubLog.info('warm relay of Up next $queueId promoted (${_sent(w)}, live ${w.live})');
       w.ensureTracks(tracks);
       return w;
     }
+    _hubLog.info('warm relay of Up next $queueId not promoted (${w.failed ? 'its fetch failed' : 'another kind or source'})');
     w.dispose();
     return null;
   }
@@ -246,11 +263,15 @@ class ServerHub {
     if (!identical(relay, r) || m?.relay == null) return;
     final was = m!.relay!;
     if (was.live == r.live && was.tracks.join(',') == r.tracks.join(',')) return;
+    if (was.live != r.live) _hubLog.info('relay of "${r.name}" ${r.live ? 'live' : 'not live (source away)'}');
     engine.media = m.copyWith(relay: was.copyWith(live: r.live, tracks: r.tracks));
     changed();
   }
 
   final _readRates = ReadRates();
+  var _statTicks = 0;
+
+  static String _kbs(int bytesPerSec) => '${(bytesPerSec / 1024).round()} KiB/s';
 
   /// Once a second: each member's read rate (`members[].rate`) and the
   /// relay's source rate and bitrate (`media.relay.rate` / `need`). Goes
@@ -268,6 +289,12 @@ class ServerHub {
     if (r == null || m == null || was == null || r.mediaId != engine.mediaId) return;
     r.sampleRate();
     final rate = r.rate, need = r.need(m.duration);
+    if (++_statTicks % 30 == 0 && r.live) {
+      final readers = engine.members.values.where((x) => x.rate > 0).map((x) => '${x.name} ${_kbs(x.rate)}');
+      _hubLog.info('relay stats "${r.name}": source ${_kbs(rate)}, needs ${_kbs(need)}, '
+          'buffered ${(r.cachedBytes / 1048576).toStringAsFixed(1)} MiB, ${_sent(r)}'
+          '${readers.isEmpty ? '' : '; reading: ${readers.join(', ')}'}');
+    }
     if (rate != was.rate || need != was.need) {
       engine.media = m.copyWith(relay: was.copyWith(rate: rate, need: need));
     }
@@ -275,6 +302,14 @@ class ServerHub {
 
   bool isHostKey(String key) => hostKey.isNotEmpty && key == hostKey;
 
+  /// A member for the log: `name (id)`, never its token.
+  String who(String token) {
+    final m = engine.members[token];
+    if (m != null) return '${m.name} (${m.id})';
+    final v = session.tokens[token];
+    return v != null ? '${v.name} (no member)' : 'unknown member';
+  }
+
   /// The member a reconnecting client may take over with its old token:
   /// still known.
   EngineMember? resumable(String token) {
@@ -365,6 +400,7 @@ class ServerHub {
   }
 
   void forgetSocket(String token) {
+    if (engine.members.containsKey(token)) _hubLog.info('leave ${who(token)}');
     engine.applyLeave(token);
     session.tokens.remove(token);
     sockets.remove(token);
@@ -383,6 +419,17 @@ class ServerHub {
   }
 }
 
+/// How a swap's media plays, for the log (a link's query cut to names).
+String _swapKind(HelloMedia m) {
+  final relay = m.relay;
+  final url = (m.url ?? '').isEmpty ? '' : ' ${logUrl(m.url)}';
+  if (m.jellyfin != null) return 'Jellyfin item ${m.jellyfin!.itemId}${relay == null ? '' : ', relayed from the swapper'}';
+  if (relay == null) return url.isEmpty ? 'hosted file' : 'link, everyone fetches it:$url';
+  if (relay.fetch) return 'link, the server fetches it:$url';
+  final tracks = relay.tracks.isEmpty ? 'one file' : relay.tracks.map((t) => t.toJson().values.join('/')).join(' + ');
+  return 'through the swapper ($tracks, ${m.size} bytes)';
+}
+
 /// `GET /a/<sid>/<token>/<hash>`: a current member's picture by its
 /// content hash, for members (valid token) only. The bytes for a
 /// hash never change, so clients may cache them for good.
@@ -519,6 +566,8 @@ void mountSyncRoute(
               final swap = SwapIntent.fromJson(decoded);
               var parsed = swap.media;
               final queueId = swap.queueId;
+              _hubLog.info('swap by ${hub.who(token)}: "${parsed.name}" ${_swapKind(parsed)}'
+                  '${queueId == null ? '' : ' (Up next $queueId)'}');
               if (queueId != null) {
                 // Already put up by someone else: nothing to do.
                 if (!hub.engine.queue.has(queueId)) return;
@@ -682,6 +731,12 @@ void mountSyncRoute(
             case 'report':
               if (token == null) return;
               final report = ReportMessage.fromJson(decoded);
+              final before = hub.engine.members[token]?.error ?? '';
+              if (report.error != before && report.mediaId == hub.engine.mediaId) {
+                _hubLog.warning(report.error.isEmpty
+                    ? '${hub.who(token)}: player error cleared'
+                    : '${hub.who(token)}: cannot play media ${report.mediaId}: ${report.error}');
+              }
               hub.engine.applyReport(
                   token, report.position, report.buffered, report.eventId,
                   duration: report.duration, mediaId: report.mediaId, jf: report.jf, error: report.error);
@@ -708,8 +763,10 @@ void mountSyncRoute(
               handleQueueIntent(hub, token, ws, decoded);
           }
         } on ProtocolException catch (e) {
+          _hubLog.info('${token == null ? 'a socket' : hub.who(token)}: bad $type message: ${e.message}');
           wsErr(ws, 'bad message: ${e.message}');
-        } catch (_) {
+        } catch (e, st) {
+          _hubLog.warning('${token == null ? 'a socket' : hub.who(token)}: $type message failed: $e', e, st);
           return;
         }
       }

packages/server/lib/src/sync_server.dart

@@ -15,15 +15,19 @@ import 'session.dart';
 /// [configured], else systemd's `$STATE_DIRECTORY/yt-dlp`, else `yt-dlp`
 /// next to the server binary when that is writable (not under `dart run`),
 /// else `~/.cache/watch-together/yt-dlp`.
-String serverYtDlpDir(String configured) {
-  if (configured.isNotEmpty) return configured;
+String serverYtDlpDir(String configured) => configured.isNotEmpty ? configured : serverDataDir('yt-dlp');
+
+/// A writable folder [name] for the dedicated server's own files:
+/// `$STATE_DIRECTORY/<name>` (systemd), else next to the binary if
+/// writable, else `~/.cache/watch-together/<name>`.
+String serverDataDir(String name) {
   final sep = Platform.pathSeparator;
   final state = (Platform.environment['STATE_DIRECTORY'] ?? '').split(':').first;
-  if (state.isNotEmpty) return '$state${sep}yt-dlp';
+  if (state.isNotEmpty) return '$state$sep$name';
   final exe = File(Platform.resolvedExecutable);
-  final name = exe.uri.pathSegments.last.toLowerCase();
-  if (name != 'dart' && name != 'dart.exe' && name != 'dartaotruntime') {
-    final dir = Directory('${exe.parent.path}${sep}yt-dlp');
+  final exeName = exe.uri.pathSegments.last.toLowerCase();
+  if (exeName != 'dart' && exeName != 'dart.exe' && exeName != 'dartaotruntime') {
+    final dir = Directory('${exe.parent.path}$sep$name');
     try {
       dir.createSync(recursive: true);
       final probe = File('${dir.path}$sep.writable')..writeAsStringSync('');
@@ -32,7 +36,7 @@ String serverYtDlpDir(String configured) {
     } catch (_) {}
   }
   final home = Platform.environment['HOME'] ?? Platform.environment['USERPROFILE'] ?? '.';
-  return '$home$sep.cache${sep}watch-together${sep}yt-dlp';
+  return '$home$sep.cache${sep}watch-together$sep$name';
 }
 
 class SyncServer {
@@ -93,12 +97,15 @@ class SyncServer {
         })),
       );
     });
-    mountSessionMediaRoute(_app, sessions);
-    mountRelayRoutes(_app, sessions, relayAt: hub.relayAt, sourceOf: hub.sourceOf);
+    final requests = MediaRequestLog();
+    void logRequest(String token, MediaLog log) => requests(hub.who(token), log);
+    mountSessionMediaRoute(_app, sessions, onLog: logRequest);
+    mountRelayRoutes(_app, sessions, relayAt: hub.relayAt, sourceOf: hub.sourceOf, onLog: logRequest);
     mountAvatarRoute(_app, hub);
     mountArtRoute(_app, hub);
     mountJellyfinRelayRoute(
-        _app, sessions, () => hub.jellyfin, () => _relayClient ??= HttpClient(), next: () => hub.nextJellyfinRef);
+        _app, sessions, () => hub.jellyfin, () => _relayClient ??= HttpClient(),
+        next: () => hub.nextJellyfinRef, onLog: logRequest);
     // advertiseHost is only an explicit override; otherwise echo what the client dialled.
     String authority(String dialledHost) => config.advertiseHost.isNotEmpty
         ? '${config.advertiseHost}:$boundPort'