Iterate before or inside a Resque task?

Question

I have 2 models: User and Group Every time a user joins a group, an email gets sent to all members of that group. I have a Resque worker that takes care of sending emails in the background.

The question is the following: Should I iterate before or inside the Resque task?

Example 1 (before):

# inside controller action
@group = Group.find(params[:group_id])
@group.users.each do |user|
    Resque.enqueue(EmailSender, {:user_id => user.id})
end

# inside worker
class EmailSender
  @queue = :emails_queue
  def self.perform(args = {})
    user = User.find(args['user_id'])
    Sender.send('new_member', {:user => user}).deliver
  end
end

Or

Example 2 (inside):

# inside controller action
@group = Group.find(params[:group_id])
Resque.enqueue(EmailSender, {:group_id => @group.id})

# inside worker
class EmailSender
  @queue = :emails_queue
  def self.perform(args = {})
    group = Group.find(args['group_id'])
    group.users.each do |user|
        Sender.send('new_member', {:user => user}).deliver
    end
  end
end

Should I go with example 1 or example 2?

Thank you

Answer 1

You should use Example 1 (before) for the following reasons:

1. It's easier to debug because you can see all the important logic in one place. Example 2 splits up an important feature (emailing all members of the group) into two separate places.

2. It is more flexible. Suppose you want to send a similar (or the same) email in a different context? This way, you can use the same Resque class rather than creating a new one.

3. (As another commenter pointed out) If an error occurs in your Resque class, it will retry. You probably want it to only retry a single email, not the whole batch. So, the Resque job should only be responsible to send one email.