TODO

Tries number should be an option

DetachedCarrot

A port of SimplifiedStarling plugin for push&pop active_record tasks to RabbitMQ.

SimplifiedStarling is a very cool plugin that works on StarlingMQ, since Starling presented some problems with the latest versions of memcached-client i decided to work on porting SimplifiedStarling to work on RabbitMQ.

This plugin works with carrot gem a great client for synchronous amqp. so what makes DetachedCarrot is simply detach the process and push AR tasks in the same way as SimplifiedStarling does. so probably the switch to ss to dc should be transparent.

Dependencies & requisites

Erlang: The lang

RabbitMQ: A Erlang Message Queue

AMQP: amqp gem

Carrot: synchronous amqp client gem

JSON: Json gem

Daemons: deamons gem

Getting Started

Install

sudo gem install amqp
sudo gem install famoseagle-carrot
sudo gem install json
sudo gem install daemons

Install this Rails plugin as usual. script/plugin install git@github.com:rorrego/detached-carrot.git

Start RabbitMQ

$  sudo rabbitmq-server

Usage

Example 1, Push a +newsletter+ job into +rabbitMQ+. Newsletter.find(params[:id]).push('deliver')

Example 2, Confirm an +order+ payment and push into +rabbitMQ+ an stock recalculation job. Stock.push('recalculate')

Example 3 , Push a task with options. Repository.push :generate, { :token => token }

Capistrano

 namespace :carrot do
  task :start, :roles => :your_server do
    invoke_command " RAILS_ENV=production #{deploy_to}/current/script/detached_carrot start" , :via => run_method
  end
  task :stop, :roles => :your_server do
    invoke_command " RAILS_ENV=production #{deploy_to}/current/script/detached_carrot stop" , :via => run_method
  end  
 end

log

Each time a job is pushed and popped to the queue is logged.

[2008-06-30 11:06:03] Pushed dispatch order
[2008-06-30 11:06:03] Popped dispatch order

If database connection goes down or dies after a few hours of inactivity database connection will be restored and job will be processed.

[2008-06-30 11:06:42] Pushed rebuild Page 3
[2008-06-30 11:06:42] WARNING Database connection gone, reconnecting & retrying.
                      {:type=>"Order", :task=>"dispatch", :id=>nil}
[2008-06-30 11:06:44] Popped rebuild Page 3

If the record you're trying to process is removed from the database before the queue is processed you'll see a warning on the logs.

[2008-06-30 11:06:50] Pushed rebuild Page 3
[2008-06-30 11:06:50] WARNING Page#3 gone from database.

Diving In

[simplifiedStarling] (http://github.com/fesplugas/simplified_starling/tree/master)

[carrot] (http://github.com/famoseagle/carrot/tree/master)

[a nice-quick guide about installing erlang, rabbit and nanites] (http://github.com/ezmobius/nanite/tree/master)

Acknowledgments

Amos Elliston,  author of carrot gem, a nice synchronous amqp client
Francesc Esplugas Marti, for his cool SimplifiedStarling plugin 
Joe Van Dyk for his work on adding options to tasks, Tanga.com LLC

rorrego / detached-carrot