Add and install delayed_job gem

db/migrate/20170926083816_create_delayed_jobs.rb

@@ -0,0 +1,22 @@
+class CreateDelayedJobs < ActiveRecord::Migration[5.0]
+  def self.up
+    create_table :delayed_jobs, force: true do |table|
+      table.integer :priority, default: 0, null: false # Allows some jobs to jump to the front of the queue
+      table.integer :attempts, default: 0, null: false # Provides for retries, but still fail eventually.
+      table.text :handler,                 null: false # YAML-encoded string of the object that will do work
+      table.text :last_error                           # reason for last failure (See Note below)
+      table.datetime :run_at                           # When to run. Could be Time.zone.now for immediately, or sometime in the future.
+      table.datetime :locked_at                        # Set when a client is working on this object
+      table.datetime :failed_at                        # Set when all retries have failed (actually, by default, the record is deleted instead)
+      table.string :locked_by                          # Who is working on this object (if locked)
+      table.string :queue                              # The name of the queue this job is in
+      table.timestamps null: true
+    end
+
+    add_index :delayed_jobs, [:priority, :run_at], name: "delayed_jobs_priority"
+  end
+
+  def self.down
+    drop_table :delayed_jobs
+  end
+end