Rate limited the bulk song downloads

libremsonic/app.py

@@ -346,8 +346,14 @@ class LibremsonicApp(Gtk.Application):
     def save_play_queue(self):
         position = self.state.song_progress
         self.last_play_queue_update = position
-        CacheManager.executor.submit(lambda: CacheManager.save_play_queue(
-            id=self.state.play_queue,
-            current=self.state.current_song.id,
-            position=math.floor(position * 1000),
-        ))
+
+        current_server = self.state.config.current_server
+        current_server = self.state.config.servers[current_server]
+
+        if current_server.sync_enabled:
+            CacheManager.executor.submit(
+                CacheManager.save_play_queue,
+                id=self.state.play_queue,
+                current=self.state.current_song.id,
+                position=math.floor(position * 1000),
+            )

libremsonic/cache_manager.py

@@ -66,6 +66,9 @@ class CacheManager(metaclass=Singleton):
         download_set_lock = threading.Lock()
         current_downloads: Set[Path] = set()
 
+        # TODO make this configurable.
+        download_limiter_semaphore = threading.Semaphore(5)
+
         def __init__(
                 self,
                 app_config: AppConfiguration,
@@ -226,6 +229,33 @@ class CacheManager(metaclass=Singleton):
 
             return CacheManager.executor.submit(do_get_playlist)
 
+        def batch_download_songs(
+                self,
+                song_ids: List[int],
+                before_download: Callable[[], None],
+                on_song_download_complete: Callable[[int], None],
+        ) -> Future:
+            def do_download_song(song_id):
+                # Do the actual download.
+                song_details_future = CacheManager.get_song_details(song_id)
+                song_filename_future = CacheManager.get_song_filename(
+                    song_details_future.result(),
+                    before_download=before_download,
+                )
+
+                def filename_future_done(f):
+                    on_song_download_complete(song_id)
+                    self.download_limiter_semaphore.release()
+
+                song_filename_future.add_done_callback(filename_future_done)
+
+            def do_batch_download_songs():
+                for song_id in song_ids:
+                    self.download_limiter_semaphore.acquire()
+                    CacheManager.executor.submit(do_download_song, song_id)
+
+            return CacheManager.executor.submit(do_batch_download_songs)
+
         def get_cover_art_filename(
                 self,
                 id: str,

libremsonic/ui/playlists.py

@@ -321,21 +321,15 @@ class PlaylistsPanel(Gtk.Paned):
         playlist = self.playlist_map[
             self.playlist_list.get_selected_row().get_index()]
 
-        def do_download_song(song: Child):
-            song_filename_future = CacheManager.get_song_filename(
-                song,
-                before_download=lambda: self.update_playlist_view(playlist.id),
-            )
+        def download_state_change(*args):
+            GLib.idle_add(self.update_playlist_view, playlist.id)
 
-            def on_song_download_complete(f):
-                self.update_playlist_view(playlist)
-
-            song_filename_future.add_done_callback(on_song_download_complete)
-
-        for song in self.playlist_song_model:
-            song_details_future = CacheManager.get_song_details(song[-1])
-            song_details_future.add_done_callback(
-                lambda f: do_download_song(f.result()), )
+        song_ids = [s[-1] for s in self.playlist_song_model]
+        CacheManager.batch_download_songs(
+            song_ids,
+            before_download=download_state_change,
+            on_song_download_complete=download_state_change,
+        )
 
     def on_view_refresh_click(self, button):
         playlist = self.playlist_map[