Fix LastFM rate limiting dropping scrobbles (f91fdd53 follow-up)

CHANGELOG.org

@@ -35,6 +35,15 @@ Two real bugs were found and fixed:
 Tests added in `tests/scrobbles_tests/test_lastfm.py` (5 tests) covering
 dedup-by-timestamp, creation, and dispatch resume/no-resume behavior.
 
+A follow-up fix on 2026-08-08: the per-scrobble `track.getDuration`/
+`getMbid` API calls in `get_last_scrobbles` exhausted Last.fm's rate limit
+during large imports, raising `WSError` for almost every track and dropping
+the whole scrobble (the artist lookup lived in the same `try`, so any failure
+left `artist` unset). Artist now comes straight from the recent-tracks
+response (no API call), duration/MBID enrichment is best-effort, and
+enrichment calls are throttled to ~0.2s each. Test added for the
+artist-survives-enrichment-failure path.
+
 ** DONE [#B] Fix LookupError on scrobble start/long-plays views :bug:scrobbles:videos:
 :PROPERTIES:
 :ID:       868e2a91-c974-4656-a8ae-b90a1f94ae74

tests/scrobbles_tests/test_lastfm.py

@@ -1,6 +1,7 @@
 from datetime import datetime, timedelta
 from unittest.mock import MagicMock, patch
 
+import pylast
 import pytest
 import pytz
 from django.contrib.auth import get_user_model
@@ -62,6 +63,44 @@ def mock_track_find_or_create():
         yield mock_find
 
 
+def make_pylast_scrobble(artist, title, timestamp, album="Emotion"):
+    track = MagicMock()
+    artist_mock = MagicMock()
+    artist_mock.name = artist
+    track.artist = artist_mock
+    track.title = title
+    scrobble = MagicMock()
+    scrobble.track = track
+    scrobble.album = album
+    scrobble.timestamp = str(int(timestamp.timestamp()))
+    return scrobble
+
+
+class TestGetLastScrobbles:
+    @pytest.mark.django_db
+    def test_artist_used_when_enrichment_fails(self, lfm_user, mock_lastfm_network):
+        timestamp = datetime(2023, 2, 15, 12, 0, 0, tzinfo=UTC)
+        scrobble = make_pylast_scrobble("Carly Rae Jepsen", "Emotion", timestamp)
+        # Enrichment (duration/mbid) hits Last.fm's rate limit, but the
+        # artist from the recent-tracks response must still be used.
+        scrobble.track.get_duration.side_effect = pylast.WSError(
+            None, 429, "rate limited"
+        )
+        scrobble.track.get_mbid.side_effect = pylast.WSError(None, 429, "rate limited")
+
+        lastfm = LastFM(lfm_user)
+        lastfm.user.get_recent_tracks.return_value = [scrobble]
+        with patch("scrobbles.importers.lastfm.time.sleep"):
+            parsed = lastfm.get_last_scrobbles()
+
+        assert len(parsed) == 1
+        assert parsed[0]["artist"] == "Carly Rae Jepsen"
+        assert parsed[0]["title"] == "Emotion"
+        assert parsed[0]["run_time_seconds"] is None
+        assert parsed[0]["mbid"] is None
+        assert parsed[0]["timestamp"] == timestamp
+
+
 class TestImportFromLastfm:
     @pytest.mark.django_db
     def test_import_creates_scrobble(

vrobbler/apps/scrobbles/importers/lastfm.py

@@ -1,5 +1,6 @@
 import calendar
 import logging
+import time
 from datetime import datetime, timedelta
 
 import pylast
@@ -138,30 +139,38 @@ class LastFM:
 
         for scrobble in found_scrobbles:
             logger.info(f"Processing {scrobble}")
+            log_dict = {"scrobble": scrobble}
+
+            # Artist/title/album come from the recent-tracks response itself,
+            # no extra API call required.
+            artist = scrobble.track.artist.name if scrobble.track.artist else None
+            log_dict["artist"] = artist
+
+            # Duration and MBID require a per-track `getInfo` API call, which
+            # quickly exhausts Last.fm's rate limit for large historical
+            # imports. Treat them as best-effort so one failure doesn't drop
+            # the whole scrobble.
             run_time = None
             mbid = None
-            artist = None
-
-            log_dict = {"scrobble": scrobble}
             try:
                 run_time = int(scrobble.track.get_duration() / 1000)
                 mbid = scrobble.track.get_mbid()
-                artist = scrobble.track.get_artist().name
-                log_dict["artist"] = artist
                 log_dict["mbid"] = mbid
                 log_dict["run_time"] = run_time
             except pylast.MalformedResponseError as e:
                 logger.warning(e)
             except pylast.WSError as e:
                 logger.info(
-                    "LastFM barfed trying to get the track for {scrobble.track}",
+                    f"LastFM barfed trying to enrich {scrobble.track}", extra=log_dict
-                    extra=log_dict,
                 )
             except pylast.NetworkError as e:
                 logger.info(
-                    "LastFM barfed trying to get the track for {scrobble.track}",
+                    f"LastFM barfed trying to enrich {scrobble.track}", extra=log_dict
-                    extra=log_dict,
                 )
+            finally:
+                # Last.fm rate limit is ~5 req/sec; keep per-track enrichment
+                # calls spaced out so large imports don't trip it.
+                time.sleep(0.2)
 
             if not artist:
                 logger.info(