Threaded delayed_job

gistfile1.rb

# Threaded delayed_job. Useful for Heroku where each process/dyno costs money.
# run "rake jobs:threaded_work[4]" to start 4 worker threads

namespace :jobs do
  desc "Start several delayed_job workers."
  task :threaded_work, [:num_workers]  => :environment do |t,args|
    args.with_defaults(:num_workers  => 1)
    threads = []
    workers = []
    workersSemaphore = Mutex.new

    (1..args.num_workers.to_i).each do |i|
      puts "Starting worker #{i}"
      threads << Thread.new() {
        worker = Delayed::Worker.new(:min_priority => ENV['MIN_PRIORITY'], :max_priority => ENV['MAX_PRIORITY'])
        worker.name_prefix = "thread_" + i.to_s + "_"
        workersSemaphore.synchronize { workers << worker }
        worker.start
      }
      puts "Worker #{i} started"
    end

    # wait for all the threads to start (since they also trap TERM/INT)
    sleep 3
    trap('TERM') { puts 'Exiting all...'; workers.each {|w| puts "exiting " + w.name; w.stop} }
    trap('INT')  { puts 'Exiting all...'; workers.each {|w| puts "exiting " + w.name; w.stop} }

    threads.each { |aThread|  aThread.join }
    puts "all workers stopped"
  end
end