Removes stale data before doing repopulation

This probably is only an issue when there are very few users, like my
test instance

bookwyrm/redis_store.py

@@ -65,6 +65,10 @@ class RedisStore(ABC):
         pipeline = r.pipeline()
         queryset = self.get_objects_for_store(store)
 
+        # first, remove everything currently in it
+        pipeline.delete(store)
+
+        # now, add everything back
         for obj in queryset[: self.max_length]:
             pipeline.zadd(store, self.get_value(obj))
 

bookwyrm/suggested_users.py

@@ -1,5 +1,6 @@
 """ store recommended follows in redis """
 import math
+import logging
 from django.dispatch import receiver
 from django.db.models import signals, Count, Q
 
@@ -8,6 +9,9 @@ from bookwyrm.redis_store import RedisStore, r
 from bookwyrm.tasks import app
 
 
+logger = logging.getLogger(__name__)
+
+
 class SuggestedUsers(RedisStore):
     """suggested users for a user"""
 
@@ -84,7 +88,12 @@ class SuggestedUsers(RedisStore):
         # annotate users with mutuals and shared book counts
         for user_id, rank in values[:5]:
             counts = self.get_counts_from_rank(rank)
-            user = models.User.objects.get(id=user_id)
+            try:
+                user = models.User.objects.get(id=user_id)
+            except models.User.DoesNotExist as err:
+                # if this happens, the suggestions are janked way up
+                logger.exception(err)
+                continue
             user.mutuals = counts["mutuals"]
             user.shared_books = counts["shared_books"]
             results.append(user)