Cache active_user_ids() more directly.

We now have a dedicated cache for active_user_ids() that only
stores a list of user_ids.

Before this commit, active_user_ids() used a cache of UserProfile
dictionaries, so it incurred unnecessary deserialization costs for
all the user fields that it sliced away in a list comprehension.

Because the cache is skinnier here, we also need to invalidate it
less frequently.  Basically, all we care about is new users, realm
deactivations, and user deactivations.

It's hard to measure how much this will improve performance, because
the speedup for any operation here is pretty minor, but we use this
function a lot, so hopefully it will make the overall system more
healthy.

zerver/lib/actions.py

@@ -53,7 +53,7 @@ from zerver.models import Realm, RealmEmoji, Stream, UserProfile, UserActivity,
     get_realm, bulk_get_recipients, \
     email_allowed_for_realm, email_to_username, display_recipient_cache_key, \
     get_user_profile_by_email, get_user, get_stream_cache_key, \
-    UserActivityInterval, get_active_user_dicts_in_realm, get_active_streams, \
+    UserActivityInterval, active_user_ids, get_active_streams, \
     realm_filters_for_realm, RealmFilter, receives_offline_notifications, \
     get_owned_bot_dicts, \
     get_old_unclaimed_attachments, get_cross_realm_emails, \
@@ -147,10 +147,6 @@ def log_event(event):
         with open(template % ('events',), 'a') as log:
             log.write(force_str(ujson.dumps(event) + u'\n'))
 
-def active_user_ids(realm_id):
-    # type: (int) -> List[int]
-    return [userdict['id'] for userdict in get_active_user_dicts_in_realm(realm_id)]
-
 def can_access_stream_user_ids(stream):
     # type: (Stream) -> Set[int]
 

zerver/lib/cache.py

@@ -337,6 +337,10 @@ def active_user_dicts_in_realm_cache_key(realm_id):
     # type: (int) -> Text
     return u"active_user_dicts_in_realm:%s" % (realm_id,)
 
+def active_user_ids_cache_key(realm_id):
+    # type: (int) -> Text
+    return u"active_user_ids:%s" % (realm_id,)
+
 bot_dict_fields = ['id', 'full_name', 'short_name', 'bot_type', 'email',
                    'is_active', 'default_sending_stream__name',
                    'realm_id',
@@ -387,6 +391,10 @@ def flush_user_profile(sender, **kwargs):
                 set(kwargs['update_fields'])) > 0:
         cache_delete(active_user_dicts_in_realm_cache_key(user_profile.realm_id))
 
+    if kwargs.get('update_fields') is None or \
+            ('is_active' in kwargs['update_fields']):
+        cache_delete(active_user_ids_cache_key(user_profile.realm_id))
+
     if kwargs.get('updated_fields') is None or \
             'email' in kwargs['update_fields']:
         delete_display_recipient_cache(user_profile)
@@ -413,6 +421,7 @@ def flush_realm(sender, **kwargs):
 
     if realm.deactivated:
         cache_delete(active_user_dicts_in_realm_cache_key(realm.id))
+        cache_delete(active_user_ids_cache_key(realm.id))
         cache_delete(bot_dicts_in_realm_cache_key(realm))
         cache_delete(realm_alert_words_cache_key(realm))
 

zerver/models.py

@@ -19,7 +19,7 @@ from zerver.lib.cache import cache_with_key, flush_user_profile, flush_realm, \
     user_profile_by_api_key_cache_key, \
     user_profile_by_id_cache_key, user_profile_by_email_cache_key, \
     user_profile_cache_key, generic_bulk_cached_fetch, cache_set, flush_stream, \
-    display_recipient_cache_key, cache_delete, \
+    display_recipient_cache_key, cache_delete, active_user_ids_cache_key, \
     get_stream_cache_key, active_user_dicts_in_realm_cache_key, \
     bot_dicts_in_realm_cache_key, active_user_dict_fields, \
     bot_dict_fields, flush_message, bot_profile_cache_key
@@ -1530,6 +1530,15 @@ def get_active_user_dicts_in_realm(realm_id):
         is_active=True
     ).values(*active_user_dict_fields)
 
+@cache_with_key(active_user_ids_cache_key, timeout=3600*24*7)
+def active_user_ids(realm_id):
+    # type: (int) -> List[int]
+    query = UserProfile.objects.filter(
+        realm_id=realm_id,
+        is_active=True
+    ).values_list('id', flat=True)
+    return list(query)
+
 @cache_with_key(bot_dicts_in_realm_cache_key, timeout=3600*24*7)
 def get_bot_dicts_in_realm(realm):
     # type: (Realm) -> List[Dict[str, Any]]

zerver/tests/test_subs.py

@@ -36,7 +36,7 @@ from zerver.lib.test_runner import (
 
 from zerver.models import (
     get_display_recipient, Message, Realm, Recipient, Stream, Subscription,
-    DefaultStream, UserProfile, get_user_profile_by_id
+    DefaultStream, UserProfile, get_user_profile_by_id, active_user_ids,
 )
 
 from zerver.lib.actions import (
@@ -45,7 +45,7 @@ from zerver.lib.actions import (
     gather_subscriptions_helper, bulk_add_subscriptions, bulk_remove_subscriptions,
     gather_subscriptions, get_default_streams_for_realm, get_realm, get_stream,
     get_user, set_default_streams, check_stream_name,
-    create_stream_if_needed, create_streams_if_needed, active_user_ids,
+    create_stream_if_needed, create_streams_if_needed,
     do_deactivate_stream,
     stream_welcome_message,
 )