Change notifications API to use a replica (#25874)

app/controllers/api/v1/notifications_controller.rb

@@ -9,8 +9,12 @@ class Api::V1::NotificationsController < Api::BaseController
   DEFAULT_NOTIFICATIONS_LIMIT = 40
 
   def index
-    @notifications = load_notifications
+    with_read_replica do
-    render json: @notifications, each_serializer: REST::NotificationSerializer, relationships: StatusRelationshipsPresenter.new(target_statuses_from_notifications, current_user&.account_id)
+      @notifications = load_notifications
+      @relationships = StatusRelationshipsPresenter.new(target_statuses_from_notifications, current_user&.account_id)
+    end
+
+    render json: @notifications, each_serializer: REST::NotificationSerializer, relationships: @relationships
   end
 
   def show

app/controllers/api/v1/timelines/home_controller.rb

@@ -6,7 +6,7 @@ class Api::V1::Timelines::HomeController < Api::BaseController
   after_action :insert_pagination_headers, unless: -> { @statuses.empty? }
 
   def show
-    ApplicationRecord.connected_to(role: :read, prevent_writes: true) do
+    with_read_replica do
       @statuses = load_statuses
       @relationships = StatusRelationshipsPresenter.new(@statuses, current_user&.account_id)
     end

app/controllers/application_controller.rb

@@ -10,6 +10,7 @@ class ApplicationController < ActionController::Base
   include SessionTrackingConcern
   include CacheConcern
   include DomainControlHelper
+  include DatabaseHelper
 
   helper_method :current_account
   helper_method :current_session

app/helpers/database_helper.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module DatabaseHelper
+  def with_read_replica(&block)
+    ApplicationRecord.connected_to(role: :read, prevent_writes: true, &block)
+  end
+
+  def with_primary(&block)
+    ApplicationRecord.connected_to(role: :primary, &block)
+  end
+end

app/workers/feed_insert_worker.rb

@@ -2,9 +2,10 @@
 
 class FeedInsertWorker
   include Sidekiq::Worker
+  include DatabaseHelper
 
   def perform(status_id, id, type = 'home', options = {})
-    ApplicationRecord.connected_to(role: :primary) do
+    with_primary do
       @type      = type.to_sym
       @status    = Status.find(status_id)
       @options   = options.symbolize_keys
@@ -18,7 +19,7 @@ class FeedInsertWorker
       end
     end
 
-    ApplicationRecord.connected_to(role: :read, prevent_writes: true) do
+    with_read_replica do
       check_and_insert
     end
   rescue ActiveRecord::RecordNotFound

app/workers/merge_worker.rb

@@ -3,14 +3,15 @@
 class MergeWorker
   include Sidekiq::Worker
   include Redisable
+  include DatabaseHelper
 
   def perform(from_account_id, into_account_id)
-    ApplicationRecord.connected_to(role: :primary) do
+    with_primary do
       @from_account = Account.find(from_account_id)
       @into_account = Account.find(into_account_id)
     end
 
-    ApplicationRecord.connected_to(role: :read, prevent_writes: true) do
+    with_read_replica do
       FeedManager.instance.merge_into_home(@from_account, @into_account)
     end
   rescue ActiveRecord::RecordNotFound

app/workers/regeneration_worker.rb

@@ -2,15 +2,16 @@
 
 class RegenerationWorker
   include Sidekiq::Worker
+  include DatabaseHelper
 
   sidekiq_options lock: :until_executed
 
   def perform(account_id, _ = :home)
-    ApplicationRecord.connected_to(role: :primary) do
+    with_primary do
       @account = Account.find(account_id)
     end
 
-    ApplicationRecord.connected_to(role: :read, prevent_writes: true) do
+    with_read_replica do
       PrecomputeFeedService.new.call(@account)
     end
   rescue ActiveRecord::RecordNotFound

app/workers/unmerge_worker.rb

@@ -2,16 +2,17 @@
 
 class UnmergeWorker
   include Sidekiq::Worker
+  include DatabaseHelper
 
   sidekiq_options queue: 'pull'
 
   def perform(from_account_id, into_account_id)
-    ApplicationRecord.connected_to(role: :primary) do
+    with_primary do
       @from_account = Account.find(from_account_id)
       @into_account = Account.find(into_account_id)
     end
 
-    ApplicationRecord.connected_to(role: :read, prevent_writes: true) do
+    with_read_replica do
       FeedManager.instance.unmerge_from_home(@from_account, @into_account)
     end
   rescue ActiveRecord::RecordNotFound