Parallelize candidate lookup for metadata plugins.

beets/metadata_plugins.py

@@ -9,6 +9,7 @@
 
 import abc
 import re
+from concurrent.futures import ThreadPoolExecutor, as_completed
 from contextlib import contextmanager
 from functools import cache, cached_property, wraps
 from typing import (
@@ -79,10 +80,28 @@ def _yield_from_plugins(
 
     @wraps(func)
     def wrapper(*args, **kwargs) -> Iterator[Ret]:
-        for plugin in find_metadata_source_plugins():
-            method = getattr(plugin, method_name)
-            with maybe_handle_plugin_error(plugin, method_name):
-                yield from filter(None, method(*args, **kwargs))
+        # Run plugin methods concurrently for faster I/O-bound lookups.
+        with ThreadPoolExecutor() as executor:
+            futures = {
+                executor.submit(
+                    # Evaluate iterator with list such that results are ready when
+                    # future.result() is called.
+                    lambda *args, **kwargs: list(
+                        getattr(plugin, method_name)(
+                            *args,
+                            **kwargs,
+                        )
+                    ),
+                    *args,
+                    **kwargs,
+                ): plugin
+                for plugin in find_metadata_source_plugins()
+            }
+
+            for future in as_completed(futures):
+                plugin = futures[future]
+                with maybe_handle_plugin_error(plugin, method_name):
+                    yield from filter(None, future.result())
 
     return wrapper
 

docs/changelog.rst

@@ -35,6 +35,9 @@ New features
   CLI flag to skip re-fetching lyrics for tracks that already have synced
   lyrics, even when ``force`` is enabled. :bug:`5249`
 - :doc:`plugins/musicbrainz`: Use aliases for artist credit.
+- Metadata source plugin searches and lookups are now executed concurrently,
+  speeding up lookups when multiple plugins (e.g. MusicBrainz and Spotify) are
+  enabled.
 
 Bug fixes
 ~~~~~~~~~