Rerun task is gem for checking if your rake task was executed successfully. You have to place all your rake code to WatchProcess.new("task_name").call{}. I write below some examples.

task :dummy_task => :environment do
	WatchProcess.new("task_name").call do
		# your code write here 		
	end
end

Now if you run rake task, then is created pid-files of your process. To your crontab place task, which every 5th minute check if all task done successfully.

If you use as non-rails app, you have to copy /bin/rerun_task_crontab.rb from gem to your app

*/5 * * * * ruby /path/to/the/your-app/bin/rerun_task_crontab.rb

If you use it in rails app, you can use rails runner

*/5 * * * * cd path/to/your-app; bundle exec rails runner RerunTask::UnfinishedRunner.crontab_retry

In this version is not allowed to run same process in same time.