[Backgroundrb-devel] Using BackgrounDRb to replace nested loops?

Ezra Zygmuntowicz ezmobius at gmail.com
Thu Jul 13 23:11:36 EDT 2006


Hi-

	Answers inline:

On Jul 13, 2006, at 5:22 PM, Jacob Patton wrote:

> In response to my Rails Weenie post today[1], someone mentioned that
> I try BackgrounDRb to help take the strain off my application.
>
> 1: http://rails.techno-weenie.net/question/2006/7/13/nested-loops-
> best-way-to-send-messages-to-blog-subscribers
>
> I've just tried to install and use BackgrounDRb with my app, but I'm
> afraid that I'm not too versed in running processes like these, and I
> can't get the caching to work--I get this error: private method
> `cache' called for #<BackgrounDRb::MiddleMan:
> 0x254f9b0>:BackgrounDRb::MiddleMan

	I apologize for this. A recent change introduced this bug. Please  
svn up or co the plugin again and try again. Caching will work as  
advertised now. But I don't think caching is the answer to your problem.

	I think you would be best served by creating a worker class that did  
the compilation of messages and sent the emails in the backgroundrb  
server. I also think that every 5 or 10 minutes is real time enough  
for most things like this. So you might be better served by building  
and sending out the email digests at intervals and not with every  
time a post gets updated.

	So since you need to use ActionMailer, which in turn needs  
ActionView, you will want to pull most of rails into your drb server  
so you can make all this happen. So add this line to your script/ 
backgroundrb/start script at the top after the boot.rb require line:

require File.dirname(__FILE__) + "/../../config/environment.rb"

Then build a worker class that does the processing and sending of  
emails in the do_work method.

class EmailWorker < BackgrounDRb::Rails

   def do_work(args)
      # loop over emails and build digest
      # loop over subscribers and send email
      #
   end

end

You will need a cron job to fire off this workers method every 5 or  
10 minutes like this:

#!/usr/bin/env ruby
require "drb"
DRb.start_service
MiddleMan = DRbObject.new(nil, "druby://localhost:22222")
# setting :ttl to 600 seconds/10 minutes. Make sure you set this for  
long enough time for your worker to finish the emails
# but you need to set this so the workers will get garbage collected  
after they are done.
MiddleMan.new_worker(:class => :email_worker, :ttl => 600)



See if this gets you started and ask if you get stuck.

Cheers-
-Ezra


> <snip code>
> Best,
>
> Jacob Patton
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