Add warning in admin dashboard if some required queues are not handled (mastodon#15954)

Author: ClearlyClaire

app/controllers/admin/dashboard_controller.rb

@@ -3,7 +3,13 @@
 
 module Admin
   class DashboardController < BaseController
+    SIDEKIQ_QUEUES = %w(default push mailers pull scheduler).freeze
+
     def index
+      missing_queues = Sidekiq::ProcessSet.new.reduce(SIDEKIQ_QUEUES) { |queues, process| queues - process['queues'] }
+
+      flash.now[:alert] = I18n.t('admin.dashboard.misconfigured_sidekiq_alert', queues: missing_queues.join(', ')) unless missing_queues.empty?
+
       @users_count           = User.count
       @pending_users_count   = User.pending.count
       @registrations_week    = Redis.current.get("activity:accounts:local:#{current_week}") || 0

config/locales/en.yml

@@ -367,6 +367,7 @@ en:
       feature_timeline_preview: Timeline preview
       features: Features
       hidden_service: Federation with hidden services
+      misconfigured_sidekiq_alert: 'No Sidekiq process seems to be handling the following queues: %{queues}. Please review your Sidekiq configuration.'
       open_reports: open reports
       pending_tags: hashtags waiting for review
       pending_users: users waiting for review