How to use multi-threading in rails 3?

Question

I am sending mail to the users using actionmailer through postmark. This is my code in controller:

@users = User.where(some condition)
@product = Product.find_by_name(some name).first
for user in @users
  UserMailer.new_product_arrival(user, @product, home_url).deliver
end

and this my user_mailer.rb

def new_product_arrival(user,product,home_url)
  @from         = Settings.mailer_from_address
  @recipients   = user.login
  @sent_on      = Time.now
  @user = user
  @product = product
  @content_type = "text/html"
  @home_url = home_url
end

The problem is that if there are more than 10 users it takes a very long time because of the for loop. I need to know if we can handle this by using multi-threading or background job. I don't want to use background job, but can anyone tell me how to implement the above using multi-threading.

I am using ruby 1.8.7 and rails 3.0.7

Answer 1

There basically two ways to wrap your loop in order to get "multi-threading":

1. Spwan a thread for each delivery and join them back to the main thread

   threads = []
   for user in @users
      threads << Thread.new do
        UserMailer.new_product_arrival(user, @product, home_url).deliver
      end
   end
   threads.each(&:join)
   

2. fork over the entire rails app ( pretty messy but the rails app serving the request will respond immediately ) and have the process detached:

   process = fork do
     for user in @users
       UserMailer.new_product_arrival(user, @product, home_url).deliver
     end
     Process.kill("HUP") 
     #sends the kill signal to current Process, which is the Rails App sending your emails 
   end
   Process.detach(process)
   

Hope that helps