deliver_asap

Adds a 'deliver_asap' method to Mail::Message. This method works as the 'deliver_now' method, but transmits the mail in the background instead. Useful if one is not really at the stage where it makes sense to pay for a worker dyno on Heroku, but wants a snappy user experience when sending a signup mail, for example.

When creating a user you could send an email, without keeping the user who just signed up waiting, by doing:

AccountMailer.welcome(@user).deliver_asap

This assumes an AccountMailer that looks something like this:

class AccountMailer < ApplicationMailer
  def welcome(user)
    @user = user
    mail(to: @user.email, subject: 'Welcome to a site')
  end
end

That is all.

This gem depends on Rufus scheduler to create a 'one-time' background job. The scheduler already takes care of limiting the number of running threads, which greatly simplifies the implementation of 'deliver_asap'.