monitor children and re-fork when they exit

lib/delayed/tasks.rb

@@ -1,12 +1,56 @@
 namespace :jobs do
+  def fork_delayed(worker_index)
+    worker_name = "delayed_job.#{worker_index}"
+
+    worker_pid = fork do
+      Delayed::Worker.after_fork
+      worker = Delayed::Worker.new(@worker_options)
+      worker.name_prefix = worker_name
+      worker.start
+    end
+
+    puts "started #{worker_name} with pid=#{worker_pid}"
+
+    return worker_name, worker_pid
+  end
+
   desc "Clear the delayed_job queue."
   task :clear => :environment do
     Delayed::Job.delete_all
   end
 
   desc "Start a delayed_job worker."
   task :work => :environment_options do
-    Delayed::Worker.new(@worker_options).start
+    if @worker_options[:num_processes] == 1
+      Delayed::Worker.new(@worker_options).start
+    else
+      stop = false
+
+      Signal.trap 'TERM' do
+        stop = true
+      end
+
+      Delayed::Worker.before_fork
+
+      workers = {}
+      @worker_options[:num_processes].times do |worker_index|
+        worker_name, worker_pid = fork_delayed(worker_index)
+        workers[worker_pid] = worker_name
+      end
+
+      worker_index = @worker_options[:num_processes]
+
+      while true
+        worker_pid = Process.wait()
+        puts "worker #{workers[worker_pid]} exited - #{$?.to_s }"
+        break if stop
+
+        worker_name, worker_pid = fork_delayed(worker_index)
+        workers[worker_pid] = worker_name
+
+        worker_index = worker_index + 1
+      end
+    end
   end
 
   desc "Start a delayed_job worker and exit when all available jobs are complete."