delayed_job vs. cron

I have a system where users come in to go through an application process that has multiple parts - sometimes users will save their progress and come back later.

I want to send users an e-mail if they haven't come back in 48 hours - would it be best to do this using cron, delayed_job, or whenever?

I've noticed that whenever I run operations in the console (such as bundle install or rake db:migrate) it runs cron as well, which makes me suspicious that we may have instances where users get multiple reminders in the same day.

What 开发者_JS百科are your recommendations for this?

First of all, Whenever and Cron are synonymous. All Whenever does is provide a way for you to write cronjobs using Ruby (which is awesome, I love Whenever).

Delayed_job is not the answer here. You definitely want to use cronjobs. Create a method on your Application model that will get applications which have an updated_at value of < 2.days.ago and e-mail its applicant.

def notify_stale_applicants
  @stale_applications = Application.where('updated_at < ?', 2.days.ago) # or 48.hours.ago
  @stale_applications.each do |app|
    UserMailer.notify_is_stale(app).deliver
  end
end

And your UserMailer:

def notify_is_stale(application)
  @application = application
  mail(:to => application.user.email, :from => "Application Status <status@yourdomain.com>", :subject => "You haven't finished your Application!"
end

Using whenever to create this cron:

every :day, :at => '8am' do
  runner 'Application.notify_stale_applicants'
end