DEV: Fix excessive MessageBus#last_id calls in chat (#20855)

We noticed via profiling that chat was doing N redis calls
per channel. Part of this was from the kick_message_bus_last_id
from 520d4f504b being incorrectly
passed down for DM channels rather that public channels, and the
other part was from the root MessageBus channel last_id
being fetched in ChannelSerializer for every single channel.

This commit fixes both issues, for me going from 134 redis calls
on page load to 20 locally.

Also deletes an old file missed in 12a18d4d55

plugins/chat/app/serializers/chat/channel_serializer.rb

@@ -109,14 +109,14 @@ module Chat
     end
 
     def meta
-      {
+      ids = {
-        message_bus_last_ids: {
+        channel_message_bus_last_id: channel_message_bus_last_id,
-          channel_message_bus_last_id: MessageBus.last_id("/chat/#{object.id}"),
+        new_messages: new_messages_message_bus_id,
-          new_messages: new_messages_message_bus_id,
+        new_mentions: new_mentions_message_bus_id,
-          new_mentions: new_mentions_message_bus_id,
-          kick: kick_message_bus_id,
-        },
       }
+
+      ids[:kick] = kick_message_bus_id if !object.direct_message_channel?
+      { message_bus_last_ids: ids }
     end
 
     alias_method :include_archive_topic_id?, :include_archive_status?
@@ -127,6 +127,10 @@ module Chat
 
     private
 
+    def channel_message_bus_last_id
+      @opts[:channel_message_bus_last_id] || Chat::Publisher.root_message_bus_channel(object.id)
+    end
+
     def new_messages_message_bus_id
       @opts[:new_messages_message_bus_last_id] ||
         MessageBus.last_id(Chat::Publisher.new_messages_message_bus_channel(object.id))

plugins/chat/app/serializers/chat/structured_channel_serializer.rb

@@ -15,6 +15,10 @@ module Chat
             chat_message_bus_last_ids[Chat::Publisher.new_messages_message_bus_channel(channel.id)],
           new_mentions_message_bus_last_id:
             chat_message_bus_last_ids[Chat::Publisher.new_mentions_message_bus_channel(channel.id)],
+          kick_message_bus_last_id:
+            chat_message_bus_last_ids[Chat::Publisher.kick_users_message_bus_channel(channel.id)],
+          channel_message_bus_last_id:
+            chat_message_bus_last_ids[Chat::Publisher.root_message_bus_channel(channel.id)],
         )
       end
     end
@@ -30,8 +34,8 @@ module Chat
             chat_message_bus_last_ids[Chat::Publisher.new_messages_message_bus_channel(channel.id)],
           new_mentions_message_bus_last_id:
             chat_message_bus_last_ids[Chat::Publisher.new_mentions_message_bus_channel(channel.id)],
-          kick_message_bus_last_id:
+          channel_message_bus_last_id:
-            chat_message_bus_last_ids[Chat::Publisher.kick_users_message_bus_channel(channel.id)],
+            chat_message_bus_last_ids[Chat::Publisher.root_message_bus_channel(channel.id)],
         )
       end
     end
@@ -87,11 +91,13 @@ module Chat
             message_bus_channels.push(Chat::Publisher.new_messages_message_bus_channel(channel.id))
             message_bus_channels.push(Chat::Publisher.new_mentions_message_bus_channel(channel.id))
             message_bus_channels.push(Chat::Publisher.kick_users_message_bus_channel(channel.id))
+            message_bus_channels.push(Chat::Publisher.root_message_bus_channel(channel.id))
           end
 
           object[:direct_message_channels].each do |channel|
             message_bus_channels.push(Chat::Publisher.new_messages_message_bus_channel(channel.id))
             message_bus_channels.push(Chat::Publisher.new_mentions_message_bus_channel(channel.id))
+            message_bus_channels.push(Chat::Publisher.root_message_bus_channel(channel.id))
           end
 
           MessageBus.last_ids(*message_bus_channels)

plugins/chat/app/serializers/chat/view_serializer.rb

@@ -24,7 +24,8 @@ module Chat
         can_moderate: scope.can_moderate_chat?(object.chat_channel.chatable),
         can_delete_self: scope.can_delete_own_chats?(object.chat_channel.chatable),
         can_delete_others: scope.can_delete_other_chats?(object.chat_channel.chatable),
-        channel_message_bus_last_id: MessageBus.last_id("/chat/#{object.chat_channel.id}"),
+        channel_message_bus_last_id:
+          Chat::Publisher.root_message_bus_channel(object.chat_channel.id),
       }
       meta_hash[
         :can_load_more_past

plugins/chat/app/serializers/chat_channel_serializer.rb

@@ -1,143 +0,0 @@
-# frozen_string_literal: true
-
-class ChatChannelSerializer < ApplicationSerializer
-  attributes :id,
-             :auto_join_users,
-             :allow_channel_wide_mentions,
-             :chatable,
-             :chatable_id,
-             :chatable_type,
-             :chatable_url,
-             :description,
-             :title,
-             :slug,
-             :last_message_sent_at,
-             :status,
-             :archive_failed,
-             :archive_completed,
-             :archived_messages,
-             :total_messages,
-             :archive_topic_id,
-             :memberships_count,
-             :current_user_membership,
-             :meta,
-             :threading_enabled
-
-  def threading_enabled
-    SiteSetting.enable_experimental_chat_threaded_discussions && object.threading_enabled
-  end
-
-  def initialize(object, opts)
-    super(object, opts)
-
-    @opts = opts
-    @current_user_membership = opts[:membership]
-  end
-
-  def include_description?
-    object.description.present?
-  end
-
-  def memberships_count
-    object.user_count
-  end
-
-  def chatable_url
-    object.chatable_url
-  end
-
-  def title
-    object.name || object.title(scope.user)
-  end
-
-  def chatable
-    case object.chatable_type
-    when "Category"
-      BasicCategorySerializer.new(object.chatable, root: false).as_json
-    when "DirectMessage"
-      DirectMessageSerializer.new(object.chatable, scope: scope, root: false).as_json
-    when "Site"
-      nil
-    end
-  end
-
-  def archive
-    object.chat_channel_archive
-  end
-
-  def include_archive_status?
-    !object.direct_message_channel? && scope.is_staff? && archive.present?
-  end
-
-  def archive_completed
-    archive.complete?
-  end
-
-  def archive_failed
-    archive.failed?
-  end
-
-  def archived_messages
-    archive.archived_messages
-  end
-
-  def total_messages
-    archive.total_messages
-  end
-
-  def archive_topic_id
-    archive.destination_topic_id
-  end
-
-  def include_auto_join_users?
-    scope.can_edit_chat_channel?
-  end
-
-  def include_current_user_membership?
-    @current_user_membership.present?
-  end
-
-  def current_user_membership
-    @current_user_membership.chat_channel = object
-
-    BaseChatChannelMembershipSerializer.new(
-      @current_user_membership,
-      scope: scope,
-      root: false,
-    ).as_json
-  end
-
-  def meta
-    {
-      message_bus_last_ids: {
-        new_messages: new_messages_message_bus_id,
-        new_mentions: new_mentions_message_bus_id,
-        kick: kick_message_bus_id,
-        channel_message_bus_last_id: MessageBus.last_id("/chat/#{object.id}"),
-      },
-    }
-  end
-
-  alias_method :include_archive_topic_id?, :include_archive_status?
-  alias_method :include_total_messages?, :include_archive_status?
-  alias_method :include_archived_messages?, :include_archive_status?
-  alias_method :include_archive_failed?, :include_archive_status?
-  alias_method :include_archive_completed?, :include_archive_status?
-
-  private
-
-  def new_messages_message_bus_id
-    @opts[:new_messages_message_bus_last_id] ||
-      MessageBus.last_id(Chat::Publisher.new_messages_message_bus_channel(object.id))
-  end
-
-  def new_mentions_message_bus_id
-    @opts[:new_mentions_message_bus_last_id] ||
-      MessageBus.last_id(Chat::Publisher.new_mentions_message_bus_channel(object.id))
-  end
-
-  def kick_message_bus_id
-    @opts[:kick_message_bus_last_id] ||
-      MessageBus.last_id(Chat::Publisher.kick_users_message_bus_channel(object.id))
-  end
-end

plugins/chat/app/services/chat/publisher.rb

@@ -6,6 +6,10 @@ module Chat
       "/chat/#{chat_channel_id}/new-messages"
     end
 
+    def self.root_message_bus_channel(chat_channel_id)
+      "/chat/#{chat_channel_id}"
+    end
+
     def self.publish_new!(chat_channel, chat_message, staged_id)
       content =
         Chat::MessageSerializer.new(
@@ -16,7 +20,7 @@ module Chat
       content[:staged_id] = staged_id
       permissions = permissions(chat_channel)
 
-      MessageBus.publish("/chat/#{chat_channel.id}", content.as_json, permissions)
+      MessageBus.publish(root_message_bus_channel(chat_channel.id), content.as_json, permissions)
 
       MessageBus.publish(
         self.new_messages_message_bus_channel(chat_channel.id),
@@ -40,7 +44,11 @@ module Chat
           cooked: chat_message.cooked,
         },
       }
-      MessageBus.publish("/chat/#{chat_channel.id}", content.as_json, permissions(chat_channel))
+      MessageBus.publish(
+        root_message_bus_channel(chat_channel.id),
+        content.as_json,
+        permissions(chat_channel),
+      )
     end
 
     def self.publish_edit!(chat_channel, chat_message)
@@ -50,7 +58,11 @@ module Chat
           { scope: anonymous_guardian, root: :chat_message },
         ).as_json
       content[:type] = :edit
-      MessageBus.publish("/chat/#{chat_channel.id}", content.as_json, permissions(chat_channel))
+      MessageBus.publish(
+        root_message_bus_channel(chat_channel.id),
+        content.as_json,
+        permissions(chat_channel),
+      )
     end
 
     def self.publish_refresh!(chat_channel, chat_message)
@@ -60,7 +72,11 @@ module Chat
           { scope: anonymous_guardian, root: :chat_message },
         ).as_json
       content[:type] = :refresh
-      MessageBus.publish("/chat/#{chat_channel.id}", content.as_json, permissions(chat_channel))
+      MessageBus.publish(
+        root_message_bus_channel(chat_channel.id),
+        content.as_json,
+        permissions(chat_channel),
+      )
     end
 
     def self.publish_reaction!(chat_channel, chat_message, action, user, emoji)
@@ -71,7 +87,11 @@ module Chat
         type: :reaction,
         chat_message_id: chat_message.id,
       }
-      MessageBus.publish("/chat/#{chat_channel.id}", content.as_json, permissions(chat_channel))
+      MessageBus.publish(
+        root_message_bus_channel(chat_channel.id),
+        content.as_json,
+        permissions(chat_channel),
+      )
     end
 
     def self.publish_presence!(chat_channel, user, typ)
@@ -80,7 +100,7 @@ module Chat
 
     def self.publish_delete!(chat_channel, chat_message)
       MessageBus.publish(
-        "/chat/#{chat_channel.id}",
+        root_message_bus_channel(chat_channel.id),
         { type: "delete", deleted_id: chat_message.id, deleted_at: chat_message.deleted_at },
         permissions(chat_channel),
       )
@@ -88,7 +108,7 @@ module Chat
 
     def self.publish_bulk_delete!(chat_channel, deleted_message_ids)
       MessageBus.publish(
-        "/chat/#{chat_channel.id}",
+        root_message_bus_channel(chat_channel.id),
         { typ: "bulk_delete", deleted_ids: deleted_message_ids, deleted_at: Time.zone.now },
         permissions(chat_channel),
       )
@@ -101,7 +121,11 @@ module Chat
           { scope: anonymous_guardian, root: :chat_message },
         ).as_json
       content[:type] = :restore
-      MessageBus.publish("/chat/#{chat_channel.id}", content.as_json, permissions(chat_channel))
+      MessageBus.publish(
+        root_message_bus_channel(chat_channel.id),
+        content.as_json,
+        permissions(chat_channel),
+      )
     end
 
     def self.publish_flag!(chat_message, user, reviewable, score)