#129 Custom Daemon

Sep 29, 2008 | 7 minutes | Plugins, Background Jobs

Creating a custom daemon to handle background tasks is surprisingly simple. In this episode I will make a daemon to handle dynamically scheduled tasks.

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          bash
        
sudo gem install daemons
script/plugin install git://github.com/dougal/daemon_generator.git
script/generate daemon mailer
RAILS_ENV=development lib/daemons/mailer_ctl start

          lib/daemons/mailer.rb
        
while($running) do
  mailing = Mailing.next_for_delivery
  if mailing
    mailing.deliver
  else
    sleep 15
  end
end

          mailings_controller.rb
        
def deliver
  Mailing.update(params[:id], :scheduled_at => Time.now)
  flash[:notice] = "Delivering mailing"
  redirect_to mailings_url
end

          models/mailing.rb
        
def self.next_for_delivery
  Mailing.first(:conditions => ["delivered_at IS NULL AND scheduled_at <= ?", Time.now.utc], :order => "scheduled_at")
end

def deliver
  update_attribute(:scheduled_at, nil)
  sleep 10 # placeholder for sending email
  update_attribute(:delivered_at, Time.now)
end