Use delayed_job for job queue

Gemfile

@@ -6,6 +6,7 @@ gem "dotenv-rails", groups: %i[development test]
 
 gem "rails", "5.2.1"
 
+gem "delayed_job_active_record"
 gem "dragonfly"
 gem "http"
 gem "jquery-rails"

Gemfile.lock

@@ -65,6 +65,11 @@ GEM
       safe_yaml (~> 1.0.0)
     crass (1.0.4)
     debug_inspector (0.0.3)
+    delayed_job (4.1.5)
+      activesupport (>= 3.0, < 5.3)
+    delayed_job_active_record (4.1.3)
+      activerecord (>= 3.0, < 5.3)
+      delayed_job (>= 3.0, < 5)
     diff-lcs (1.3)
     domain_name (0.5.20180417)
       unf (>= 0.0.5, < 1.0.0)
@@ -244,6 +249,7 @@ DEPENDENCIES
   better_errors
   binding_of_caller
   capybara
+  delayed_job_active_record
   dotenv-rails
   dragonfly
   http

Procfile

@@ -0,0 +1,2 @@
+web: bundle exec puma -C config/puma.rb
+worker: bundle exec rake jobs:work

bin/delayed_job

@@ -0,0 +1,5 @@
+#!/usr/bin/env ruby
+
+require File.expand_path(File.join(File.dirname(__FILE__), '..', 'config', 'environment'))
+require 'delayed/command'
+Delayed::Command.new(ARGV).daemonize

config/application.rb

@@ -26,5 +26,7 @@ module MyImages
     # ]
     # config.i18n.default_locale = :de
     config.autoload_paths += %W(#{config.root}/lib)
+
+    config.active_job.queue_adapter = :delayed_job
   end
 end

config/puma.rb

@@ -0,0 +1,15 @@
+workers Integer(ENV["WEB_CONCURRENCY"] || 2)
+threads_count = Integer(ENV["RAILS_MAX_THREADS"] || 5)
+threads threads_count, threads_count
+
+preload_app!
+
+rackup      DefaultRackup
+port        ENV["PORT"]     || 3000
+environment ENV["RACK_ENV"] || "development"
+
+on_worker_boot do
+  # Worker specific setup for Rails 4.1+
+  # See: https://devcenter.heroku.com/articles/deploying-rails-applications-with-the-puma-web-server#on-worker-boot
+  ActiveRecord::Base.establish_connection
+end

db/migrate/20180826163510_create_delayed_jobs.rb

@@ -0,0 +1,22 @@
+class CreateDelayedJobs < ActiveRecord::Migration[5.2]
+  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

db/schema.rb

@@ -10,11 +10,26 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2018_08_25_150330) do
+ActiveRecord::Schema.define(version: 2018_08_26_163510) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
 
+  create_table "delayed_jobs", force: :cascade do |t|
+    t.integer "priority", default: 0, null: false
+    t.integer "attempts", default: 0, null: false
+    t.text "handler", null: false
+    t.text "last_error"
+    t.datetime "run_at"
+    t.datetime "locked_at"
+    t.datetime "failed_at"
+    t.string "locked_by"
+    t.string "queue"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+    t.index ["priority", "run_at"], name: "delayed_jobs_priority"
+  end
+
   create_table "images", force: :cascade do |t|
     t.integer "user_id"
     t.string "image_uid"