Move some logic to the model

app/controllers/rescan_controller.rb

@@ -6,14 +6,14 @@ def show
   end
 
   def start
-    @rescan.delay(queue: :rescans).run
+    @rescan.schedule
     render json: @rescan
   end
 
   private
 
   def set_rescan
-    @rescan = RescanRunner.first || RescanRunner.create
+    @rescan = RescanRunner.instance
     authorize @rescan
   end
 end

app/models/rescan_runner.rb

@@ -11,6 +11,14 @@
 #
 
 class RescanRunner < ApplicationRecord
+  def self.instance
+    RescanRunner.first || RescanRunner.create
+  end
+
+  def schedule
+    delay(queue: :rescans).run
+  end
+
   def run
     # rubocop:disable Rails/SkipsModelValidations
     # RescanRunner doesn't have validations, and we need to use update_all to use it's atomicity

lib/tasks/rescan.rake

@@ -1,6 +1,5 @@
 namespace :rescan do
   task start: :environment do
-    rescan = RescanRunner.first || RescanRunner.create
-    rescan.delay(queue: :rescans).run
+    RescanRunner.instance.start_delayed
   end
 end