deletion: Add support for bulk message deletion events.

This is designed to have no user-facing change unless the client
declares bulk_message_deletion in its client_capabilities.

Clients that do so will receive a single bulk event for bulk deletions
of messages within a single conversation (topic or PM thread).

Backend implementation of #15285.

templates/zerver/api/changelog.md

@@ -10,6 +10,17 @@ below features are supported.
 
 ## Changes in Zulip 2.2
 
+**Feature level 13**
+
+* [`POST /register`](/api/register-queue): Added
+  `bulk_message_deletion` to supported `client_capabilities`.
+* [`GET /events`](/api/get-events-from-queue): `message_deleted`
+  events have new behavior.  The `sender` and `sender_id` fields were
+  removed, and the `message_id` field was replaced by a `message_ids`
+  list for clients with the `bulk_message_deletion` client capability.
+  All clients should upgrade; we expect `bulk_message_deletion` to be
+  required in the future.
+
 **Feature level 12**
 
 * [`GET users/{user_id}/subscriptions/{stream_id}`](/api/get-subscription-status):

version.py

@@ -29,7 +29,7 @@ DESKTOP_WARNING_VERSION = "5.2.0"
 #
 # Changes should be accompanied by documentation explaining what the
 # new level means in templates/zerver/api/changelog.md.
-API_FEATURE_LEVEL = 12
+API_FEATURE_LEVEL = 13
 
 # Bump the minor PROVISION_VERSION to indicate that folks should provision
 # only when going from an old version of the code to a newer version. Bump

zerver/lib/actions.py

@@ -251,6 +251,12 @@ STREAM_ASSIGNMENT_COLORS = [
     "#9987e1", "#e4523d", "#c2c2c2", "#4f8de4",
     "#c6a8ad", "#e7cc4d", "#c8bebf", "#a47462"]
 
+def subscriber_info(user_id: int) -> Dict[str, Any]:
+    return {
+        'id': user_id,
+        'flags': ['read']
+    }
+
 # Store an event in the log for re-importing messages
 def log_event(event: MutableMapping[str, Any]) -> None:
     if settings.EVENT_LOG_DIR is None:
@@ -4540,12 +4546,6 @@ def do_update_message(user_profile: UserProfile, message: Message,
             'flags': um.flags_list(),
         }
 
-    def subscriber_info(user_id: int) -> Dict[str, Any]:
-        return {
-            'id': user_id,
-            'flags': ['read'],
-        }
-
     # The following blocks arranges that users who are subscribed to a
     # stream and can see history from before they subscribed get
     # live-update when old messages are edited (e.g. if the user does
@@ -4584,50 +4584,45 @@ def do_update_message(user_profile: UserProfile, message: Message,
     return len(changed_messages)
 
 def do_delete_messages(realm: Realm, messages: Iterable[Message]) -> None:
+    # messages in delete_message event belong to the same topic
+    # or is a single private message, as any other behaviour is not possible with
+    # the current callers to this method.
+    messages = list(messages)
     message_ids = [message.id for message in messages]
     if not message_ids:
         return
 
-    usermessages = UserMessage.objects.filter(message_id__in=message_ids)
-    message_id_to_notifiable_users: Dict[int, List[int]] = {}
-    for um in usermessages:
-        if um.message_id not in message_id_to_notifiable_users:
-            message_id_to_notifiable_users[um.message_id] = []
-        message_id_to_notifiable_users[um.message_id].append(um.user_profile_id)
+    event: Dict[str, Any] = {
+        'type': 'delete_message',
+        'message_ids': message_ids,
+    }
 
-    events_and_users_to_notify = []
-    for message in messages:
-        message_type = "stream"
-        if not message.is_stream_message():
-            message_type = "private"
+    sample_message = messages[0]
+    message_type = "stream"
+    users_to_notify = []
+    if not sample_message.is_stream_message():
+        assert len(messages) == 1
+        message_type = "private"
+        ums = UserMessage.objects.filter(message_id__in=message_ids)
+        users_to_notify = [um.user_profile_id for um in ums]
+        # TODO: We should plan to remove `sender_id` here.
+        event['recipient_id'] = sample_message.recipient_id
+        event['sender_id'] = sample_message.sender_id
 
-        event: Dict[str, Any] = {
-            'type': 'delete_message',
-            'sender': message.sender.email,
-            'sender_id': message.sender_id,
-            'message_id': message.id,
-            'message_type': message_type,
-        }
-        if message_type == "stream":
-            event['stream_id'] = message.recipient.type_id
-            event['topic'] = message.topic_name()
-        else:
-            event['recipient_id'] = message.recipient_id
-
-        # In theory, it's possible for message_id_to_notifiable_users
-        # to not have a key for the message ID in some weird corner
-        # case where we've deleted the last user subscribed to the
-        # target stream before a bot sent a message to it, and thus
-        # there are no UserMessage objects associated with the
-        # message.
-        events_and_users_to_notify.append(
-            (event, message_id_to_notifiable_users.get(message.id, [])),
-        )
+    if message_type == "stream":
+        stream_id = sample_message.recipient.type_id
+        event['stream_id'] = stream_id
+        event['topic'] = sample_message.topic_name()
+        subscribers = get_active_subscriptions_for_stream_id(stream_id)
+        # We exclude long-term idle users, since they by definition have no active clients.
+        subscribers = subscribers.exclude(user_profile__long_term_idle=True)
+        subscribers_ids = [user.user_profile_id for user in subscribers]
+        users_to_notify = list(map(subscriber_info, subscribers_ids))
 
     move_messages_to_archive(message_ids, realm=realm)
-    for event, users_to_notify in events_and_users_to_notify:
-        # TODO: Figure out some kind of bulk event that we could send just one of?
-        send_event(realm, event, users_to_notify)
+
+    event['message_type'] = message_type
+    send_event(realm, event, users_to_notify)
 
 def do_delete_messages_by_sender(user: UserProfile) -> None:
     message_ids = list(Message.objects.filter(sender=user).values_list('id', flat=True).order_by('id'))

zerver/lib/events.py

@@ -679,6 +679,10 @@ def apply_event(state: Dict[str, Any],
                 if message_id in stream_dict:
                     stream_dict[message_id]['topic'] = topic
     elif event['type'] == "delete_message":
+        if 'message_id' in event:
+            message_ids = [event['message_id']]
+        else:
+            message_ids = event['message_ids']  # nocoverage
         max_message = Message.objects.filter(
             usermessage__user_profile=user_profile).order_by('-id').first()
         if max_message:
@@ -687,8 +691,8 @@ def apply_event(state: Dict[str, Any],
             state['max_message_id'] = -1
 
         if 'raw_unread_msgs' in state:
-            remove_id = event['message_id']
-            remove_message_id_from_unread_mgs(state['raw_unread_msgs'], remove_id)
+            for remove_id in message_ids:
+                remove_message_id_from_unread_mgs(state['raw_unread_msgs'], remove_id)
 
         # The remainder of this block is about maintaining recent_private_conversations
         if 'raw_recent_private_conversations' not in state or event['message_type'] != 'private':
@@ -705,7 +709,7 @@ def apply_event(state: Dict[str, Any],
             return
 
         old_max_message_id = state['raw_recent_private_conversations'][recipient_id]['max_message_id']
-        if old_max_message_id != event['message_id']:  # nocoverage
+        if old_max_message_id not in message_ids:  # nocoverage
             return
 
         # OK, we just deleted what had been the max_message_id for
@@ -839,6 +843,7 @@ def do_events_register(user_profile: UserProfile, user_client: Client,
     check_supported_events_narrow_filter(narrow)
 
     notification_settings_null = client_capabilities.get('notification_settings_null', False)
+    bulk_message_deletion = client_capabilities.get('bulk_message_deletion', False)
 
     if user_profile.realm.email_address_visibility != Realm.EMAIL_ADDRESS_VISIBILITY_EVERYONE:
         # If real email addresses are not available to the user, their
@@ -850,7 +855,8 @@ def do_events_register(user_profile: UserProfile, user_client: Client,
     queue_id = request_event_queue(user_profile, user_client,
                                    apply_markdown, client_gravatar, slim_presence,
                                    queue_lifespan_secs, event_types, all_public_streams,
-                                   narrow=narrow)
+                                   narrow=narrow,
+                                   bulk_message_deletion=bulk_message_deletion)
 
     if queue_id is None:
         raise JsonableError(_("Could not allocate event queue"))

zerver/openapi/zulip.yaml

@@ -3112,6 +3112,15 @@ paths:
             notification settings for stream messages).  New in Zulip
             2.1.0; in earlier Zulip releases, stream-level
             notification settings were simple booleans.
+
+          * `bulk_message_deletion`: Boolean for whether the client's
+             handler for the `delete_message` event type has been
+             updated to process the new bulk format (with a
+             `message_ids`, rather than a singleton `message_id`).
+             Otherwise, the server will send `delete_message` events
+             in a loop.  New in Zulip 2.2 (feature level 13).  This
+             capability is for backwards-compatibility; it will be
+             required in a future server release.
         schema:
           type: object
         example:

zerver/tests/test_events.py

@@ -528,6 +528,7 @@ class EventsRegisterTest(ZulipTestCase):
                  last_connection_time = time.time(),
                  narrow = []),
         )
+
         # hybrid_state = initial fetch state + re-applying events triggered by our action
         # normal_state = do action then fetch at the end (the "normal" code path)
         hybrid_state = fetch_initial_state_data(
@@ -2732,8 +2733,6 @@ class EventsRegisterTest(ZulipTestCase):
         schema_checker = self.check_events_dict([
             ('type', equals('delete_message')),
             ('message_id', check_int),
-            ('sender', check_string),
-            ('sender_id', check_int),
             ('message_type', equals("stream")),
             ('stream_id', check_int),
             ('topic', check_string),
@@ -2752,7 +2751,6 @@ class EventsRegisterTest(ZulipTestCase):
         schema_checker = self.check_events_dict([
             ('type', equals('delete_message')),
             ('message_id', check_int),
-            ('sender', check_string),
             ('sender_id', check_int),
             ('message_type', equals("private")),
             ('recipient_id', check_int),

zerver/tests/test_retention.py

@@ -895,7 +895,7 @@ class TestDoDeleteMessages(ZulipTestCase):
         with queries_captured() as queries:
             do_delete_messages(realm, messages)
         self.assertFalse(Message.objects.filter(id__in=message_ids).exists())
-        self.assert_length(queries, 37)
+        self.assert_length(queries, 18)
 
         archived_messages = ArchivedMessage.objects.filter(id__in=message_ids)
         self.assertEqual(archived_messages.count(), len(message_ids))

zerver/tornado/event_queue.py

@@ -90,7 +90,8 @@ class ClientDescriptor:
                  slim_presence: bool=False,
                  all_public_streams: bool=False,
                  lifespan_secs: int=0,
-                 narrow: Iterable[Sequence[str]]=[]) -> None:
+                 narrow: Iterable[Sequence[str]]=[],
+                 bulk_message_deletion: bool=False) -> None:
         # These objects are serialized on shutdown and restored on restart.
         # If fields are added or semantics are changed, temporary code must be
         # added to load_event_queues() to update the restored objects.
@@ -110,6 +111,7 @@ class ClientDescriptor:
         self._timeout_handle: Any = None  # TODO: should be return type of ioloop.call_later
         self.narrow = narrow
         self.narrow_filter = build_narrow_filter(narrow)
+        self.bulk_message_deletion = bulk_message_deletion
 
         # Default for lifespan_secs is DEFAULT_EVENT_QUEUE_TIMEOUT_SECS;
         # but users can set it as high as MAX_QUEUE_TIMEOUT_SECS.
@@ -132,7 +134,8 @@ class ClientDescriptor:
                     slim_presence=self.slim_presence,
                     all_public_streams=self.all_public_streams,
                     narrow=self.narrow,
-                    client_type_name=self.client_type_name)
+                    client_type_name=self.client_type_name,
+                    bulk_message_deletion=self.bulk_message_deletion)
 
     def __repr__(self) -> str:
         return f"ClientDescriptor<{self.event_queue.id}>"
@@ -161,6 +164,7 @@ class ClientDescriptor:
             d['all_public_streams'],
             d['queue_timeout'],
             d.get('narrow', []),
+            d.get('bulk_message_deletion', False),
         )
         ret.last_connection_time = d['last_connection_time']
         return ret
@@ -604,7 +608,9 @@ def request_event_queue(user_profile: UserProfile, user_client: Client, apply_ma
                         client_gravatar: bool, slim_presence: bool, queue_lifespan_secs: int,
                         event_types: Optional[Iterable[str]]=None,
                         all_public_streams: bool=False,
-                        narrow: Iterable[Sequence[str]]=[]) -> Optional[str]:
+                        narrow: Iterable[Sequence[str]]=[],
+                        bulk_message_deletion: bool=False) -> Optional[str]:
+
     if settings.TORNADO_SERVER:
         tornado_uri = get_tornado_uri(user_profile.realm)
         req = {'dont_block': 'true',
@@ -617,7 +623,9 @@ def request_event_queue(user_profile: UserProfile, user_client: Client, apply_ma
                'user_client': user_client.name,
                'narrow': ujson.dumps(narrow),
                'secret': settings.SHARED_SECRET,
-               'lifespan_secs': queue_lifespan_secs}
+               'lifespan_secs': queue_lifespan_secs,
+               'bulk_message_deletion': ujson.dumps(bulk_message_deletion)}
+
         if event_types is not None:
             req['event_types'] = ujson.dumps(event_types)
 
@@ -972,6 +980,29 @@ def process_event(event: Mapping[str, Any], users: Iterable[int]) -> None:
             if client.accepts_event(event):
                 client.add_event(event)
 
+def process_deletion_event(event: Mapping[str, Any], users: Iterable[int]) -> None:
+    for user_profile_id in users:
+        for client in get_client_descriptors_for_user(user_profile_id):
+            if not client.accepts_event(event):
+                continue
+
+            # For clients which support message deletion in bulk, we
+            # send a list of msgs_ids together, otherwise we send a
+            # delete event for each message.  All clients will be
+            # required to support bulk_message_deletion in the future;
+            # this logic is intended for backwards-compatibility only.
+            if client.bulk_message_deletion:
+                client.add_event(event)
+                continue
+
+            for message_id in event['message_ids']:
+                # We use the following rather than event.copy()
+                # because the read-only Mapping type doesn't support .copy().
+                compatibility_event = dict(event)
+                compatibility_event['message_id'] = message_id
+                del compatibility_event['message_ids']
+                client.add_event(compatibility_event)
+
 def process_message_update_event(event_template: Mapping[str, Any],
                                  users: Iterable[Mapping[str, Any]]) -> None:
     prior_mention_user_ids = set(event_template.get('prior_mention_user_ids', []))
@@ -1089,13 +1120,19 @@ def process_notification(notice: Mapping[str, Any]) -> None:
         process_message_event(event, cast(Iterable[Mapping[str, Any]], users))
     elif event['type'] == "update_message":
         process_message_update_event(event, cast(Iterable[Mapping[str, Any]], users))
-    elif event['type'] == "delete_message" and len(users) > 0 and isinstance(users[0], dict):
-        # do_delete_messages used to send events with users in dict format {"id": <int>}
-        # This block is here for compatibility with events in that format still in the queue
-        # at the time of upgrade.
-        # TODO: Remove this block in release >= 2.3.
-        user_ids = [user['id'] for user in cast(Iterable[Mapping[str, int]], users)]
-        process_event(event, user_ids)
+    elif event['type'] == "delete_message":
+        if len(users) > 0 and isinstance(users[0], dict):
+            # do_delete_messages used to send events with users in
+            # dict format {"id": <int>} This block is here for
+            # compatibility with events in that format still in the
+            # queue at the time of upgrade.
+            #
+            # TODO: Remove this block in release >= 2.3.
+            user_ids: List[int] = [user['id'] for user in
+                                   cast(List[Mapping[str, int]], users)]
+        else:
+            user_ids = cast(List[int], users)
+        process_deletion_event(event, user_ids)
     elif event['type'] == "presence":
         process_presence_event(event, cast(Iterable[int], users))
     else:

zerver/tornado/views.py

@@ -76,6 +76,8 @@ def get_events_backend(request: HttpRequest, user_profile: UserProfile,
                                                            intentionally_undocumented=True),
                        lifespan_secs: int=REQ(default=0, converter=to_non_negative_int,
                                               intentionally_undocumented=True),
+                       bulk_message_deletion: bool=REQ(default=False, validator=check_bool,
+                                                       intentionally_undocumented=True)
                        ) -> HttpResponse:
     # Extract the Tornado handler from the request
     handler: AsyncDjangoHandler = request._tornado_handler
@@ -109,7 +111,8 @@ def get_events_backend(request: HttpRequest, user_profile: UserProfile,
             all_public_streams = all_public_streams,
             queue_timeout = lifespan_secs,
             last_connection_time = time.time(),
-            narrow = narrow)
+            narrow = narrow,
+            bulk_message_deletion = bulk_message_deletion)
 
     result = fetch_events(events_query)
     if "extra_log_data" in result:

zerver/views/events_register.py

@@ -39,6 +39,7 @@ def events_register_backend(
             ("notification_settings_null", check_bool),
         ], [
             # Any new fields of `client_capabilities` should be optional. Add them here.
+            ("bulk_message_deletion", check_bool),
         ]), default=None),
         event_types: Optional[Iterable[str]]=REQ(validator=check_list(check_string), default=None),
         fetch_event_types: Optional[Iterable[str]]=REQ(validator=check_list(check_string), default=None),

zerver/views/home.py

@@ -191,6 +191,7 @@ def home_real(request: HttpRequest) -> HttpResponse:
 
     client_capabilities = {
         'notification_settings_null': True,
+        'bulk_message_deletion': False,
     }
 
     register_ret = do_events_register(user_profile, request.client,