typing: Limit typing notifications in large streams.

help/typing-notifications.md

@@ -2,8 +2,10 @@
 
 The Zulip web app displays typing notifications in [conversation
 views](/help/reading-conversations) and [**All direct
-messages**](/help/direct-messages#access-all-dms). The mobile app displays
-typing notifications in direct message conversations.
+messages**](/help/direct-messages#access-all-dms). Typing
+notifications are not shown in streams with more than 100
+subscribers. The mobile app displays typing notifications in direct
+message conversations.
 
 Typing notifications are only sent while one is actively editing text in
 the compose box. They disappear if typing is paused for several seconds,

zerver/actions/typing.py

@@ -1,5 +1,6 @@
 from typing import List
 
+from django.conf import settings
 from django.utils.translation import gettext as _
 
 from zerver.lib.exceptions import JsonableError
@@ -78,9 +79,20 @@ def do_send_stream_typing_notification(
     )
 
     # We don't notify long_term_idle subscribers.
-    subscriptions = get_active_subscriptions_for_stream_id(
+    subscriptions_query = get_active_subscriptions_for_stream_id(
         stream.id, include_deactivated_users=False
-    ).exclude(user_profile__long_term_idle=True)
-    user_ids_to_notify = set(subscriptions.values_list("user_profile_id", flat=True))
+    )
+
+    total_subscriptions = subscriptions_query.count()
+    if total_subscriptions > settings.MAX_STREAM_SIZE_FOR_TYPING_NOTIFICATIONS:
+        # TODO: Stream typing notifications are disabled in streams
+        # with too many subscribers for performance reasons.
+        return
+
+    user_ids_to_notify = set(
+        subscriptions_query.exclude(user_profile__long_term_idle=True).values_list(
+            "user_profile_id", flat=True
+        )
+    )
 
     send_event(sender.realm, event, user_ids_to_notify)

zerver/tests/test_typing.py

@@ -381,7 +381,7 @@ class TypingHappyPathTestStreams(ZulipTestCase):
             topic=topic,
         )
 
-        with self.assert_database_query_count(5):
+        with self.assert_database_query_count(6):
             with self.capture_send_event_calls(expected_num_events=1) as events:
                 result = self.api_post(sender, "/api/v1/typing", params)
         self.assert_json_success(result)
@@ -412,7 +412,7 @@ class TypingHappyPathTestStreams(ZulipTestCase):
             topic=topic,
         )
 
-        with self.assert_database_query_count(5):
+        with self.assert_database_query_count(6):
             with self.capture_send_event_calls(expected_num_events=1) as events:
                 result = self.api_post(sender, "/api/v1/typing", params)
         self.assert_json_success(result)
@@ -428,6 +428,29 @@ class TypingHappyPathTestStreams(ZulipTestCase):
         self.assertEqual("typing", event["type"])
         self.assertEqual("stop", event["op"])
 
+    def test_max_stream_size_for_typing_notifications_setting(self) -> None:
+        sender = self.example_user("hamlet")
+        stream_name = self.get_streams(sender)[0]
+        stream_id = self.get_stream_id(stream_name)
+        topic = "Some topic"
+
+        for name in ["aaron", "iago", "cordelia", "prospero", "othello", "polonius"]:
+            user = self.example_user(name)
+            self.subscribe(user, stream_name)
+
+        params = dict(
+            type="stream",
+            op="start",
+            stream_id=str(stream_id),
+            topic=topic,
+        )
+        with self.settings(MAX_STREAM_SIZE_FOR_TYPING_NOTIFICATIONS=5):
+            with self.assert_database_query_count(5):
+                with self.capture_send_event_calls(expected_num_events=0) as events:
+                    result = self.api_post(sender, "/api/v1/typing", params)
+            self.assert_json_success(result)
+            self.assert_length(events, 0)
+
     def test_notify_not_long_term_idle_subscribers_only(self) -> None:
         sender = self.example_user("hamlet")
         stream_name = self.get_streams(sender)[0]
@@ -453,7 +476,7 @@ class TypingHappyPathTestStreams(ZulipTestCase):
             topic=topic,
         )
 
-        with self.assert_database_query_count(5):
+        with self.assert_database_query_count(6):
             with self.capture_send_event_calls(expected_num_events=1) as events:
                 result = self.api_post(sender, "/api/v1/typing", params)
         self.assert_json_success(result)

zproject/default_settings.py

@@ -587,3 +587,8 @@ TYPING_STOPPED_WAIT_PERIOD_MILLISECONDS = 5000
 # How often a client should send start notifications to the server to
 # indicate that the user is still interacting with the compose UI.
 TYPING_STARTED_WAIT_PERIOD_MILLISECONDS = 10000
+
+# The maximum number of subscribers for a stream to have typing
+# notifications enabled. Default is set to avoid excessive Tornado
+# load in large organizations.
+MAX_STREAM_SIZE_FOR_TYPING_NOTIFICATIONS = 100