Delayed Job with Sinatra -- without sinatra specific gems, etc.

delayed_job.rb

#!/usr/bin/env ruby

# make this mirror your config/environment files
require File.expand_path(File.join(File.dirname(__FILE__), '..', 'dj-sinatra'))
require 'delayed/command'
Delayed::Command.new(ARGV).daemonize

dj-sinatra.rb

# Caressing DelayedJob to work with Sinatra.
# I'm not sure if there is a gem for this or not, but i'm not a big fan
# of installing gems if i don't have to -- so heres what i found to be the
# bare foundation necessary to get delayed jobs running with sinatra
# 
#   1. ./bin/delayed_job -- taken from the DJ gem's generator template but
#       modified to point to this "environment" file rather than lib/environment
#   2. log/delayed_job.log -- DJ needs this
#   3. tmp/pids -- DJ needs this
#   4. Rails.logger -- DJ needs this
#   5. RAILS_ROOT -- DJ needs this constant defined
#   6. Delayed::Worker.backend = :active_record (or Delayed::Worker.guess_backend to guess)
#   7. migration file -- can take this from github or the gem's generator templates
# 
# Debugging / Starting:
# 
#   1. ./bin/delayed_job run
#   2. irb -r ./dj-sinatra.rb
#   3. tail -f log/delayed_job.log
# 
# Console:
# 
#   Delayed::Job.enqueue SuccessfulJob.new  # => should be clean in the logs/db table
#   Delayed::Job.enqueue FailureJob.new     # => should show failure message, etc.
# 
# Author:: Rob Hurring
# Date:: 2012-12-7
# 
# I know AR/AS/DJ are out of date, but the project that needed this was running on a
# non-rails-3 server. either way, thats not the point :)

require 'rubygems'

gem 'sinatra'
gem 'activesupport', '~> 2.3.8'
gem 'activerecord', '~> 2.3.8'
gem 'delayed_job', '= 2.0.3'

require 'sinatra'
require 'logger'
require 'active_support'
require 'active_record'
require 'delayed_job'

# Global app logger
Log = Logger.new(File.expand_path('../log/app.log', __FILE__))

# DelayedJob wants us to be on rails, so it looks for stuff
# in the rails namespace -- so we emulate it a bit
module Rails
  class << self
    attr_accessor :logger
  end
end
Rails.logger = Log
ActiveRecord::Base.logger = Log

# this is used by DJ to guess where tmp/pids is located (default)
RAILS_ROOT = File.expand_path('..', __FILE__)

# Configure DelayedJob
Delayed::Worker.backend = :active_record
Delayed::Worker.destroy_failed_jobs = true
Delayed::Worker.sleep_delay = 5
Delayed::Worker.max_attempts = 5
Delayed::Worker.max_run_time = 5.minutes

# for brevity i'm not including the migration here
# you can figure that out from the README on github
# this is an existing project w/ a delayed_jobs file
ActiveRecord::Base.establish_connection({
  :adapter => 'mysql2',
  :host => 'localhost',
  :username => 'root',
  :password => '',
  :database => 'your_database_with_a_delayed_jobs_table',
})

# Jobs to test
class SuccessfulJob
  def perform
    true
  end
end

class FailureJob
  def perform
    raise "Failed!"
  end
end

########### START OF RAD SINATRA APP ########### 

get '/' do
  "blah blah blah blah"
end

Rakefile

task :environment do
  require './dj-sinatra'
end

namespace :jobs do
  desc "Clear the delayed_job queue."
  task :clear => :environment do
    Delayed::Job.delete_all
  end

  desc "Start a delayed_job worker."
  task :work => :environment do
    Delayed::Worker.new(:min_priority => ENV['MIN_PRIORITY'], :max_priority => ENV['MAX_PRIORITY']).start
  end
end

structure.sh

#!/bin/sh
# run from djsinatra folder

mkdir -p tmp/pids log bin
chmod -R a+w tmp/pids log
touch log/{app,delayed_job}.log

# place delayed_job.rb script in ./bin/delayed_job

With ActiveRecord >= 6.0 the above is no longer enough. Easiest solution is to apply this fix.