Kaboose Queue (kabqueue)
The Kaboose Queue system is designed to handle asynchronous generic tasks (or messages). The main function of this system is to take the load off the request cycle. We use this system to send out e-mail, perform intensive image or video tasks, asynchronous network operations, etc.
We had a few important things in mind when desiging this system:
- Performance
- Scalibility
- Reliability
The first item is obvious. The system needs to be fast and relatively resource friendly. For this reason, we chose the Starling queue system from Twitter (www.twitter.com).
The second item, scalibility, means that the system should:
- Be distributed. Many machines submitting tasks, and many machines processing these tasks.
- Handle a large number of requests. Each photo upload spawns resize operations for frequently used sizes. Each resize spawns off additional S3 uploads, for example.
- Support task priorities
The third item requires the system to handle failures, retry common errors, and notify us in case of major failures. Also, the system needs to surive the server dying and coming back and temporary network errors.
With the help of Starling, and our previous experience with a database-backed message queue system, I think we've achieved our goals. We look forward to the community's feedback.
Requirements
sudo gem install starling sudo gem install daemons
Installation
script/plugin install http://kabqueue.googlecode.com/svn/trunk/kabqueue
Example usage
First, you will need to create a processor file(foo.rb) in RAILS_ROOT/app/processors folder. It should be structured like so:
class FooProcessor < Kaboose::Processor
processes :some_model
def processsome_model.some_method endend
end
Each processor class must implement a process method that defines the action that needs to be processed by the queue. This method has access to the @task instance variable that is an instance of Kaboose::Task. The processes macro creates an accessor method as a shortcut for accessing ActiveRecord models specified by model_id option in the task. See Kaboose::Processor's self.processes for more info.
Configuration
You will need a kqueue.yml file in your apps config folder to specify the address and namespace of the system, for example:
address: 127.0.0.1:22122 namespace: some_namespace
Running the Kaboose Queue system
Just run ./script/queue_processor to get a list of options.
If you are using monit, here's what worked for us:
check process queue-processor with pidfile /path/to/queue_processor.pid
group qtp
start program = "PATH/queue_processor start -d -e production -c CWD -u USER -g GROUP"
stop program = "PATH/queue_processor stop -d -e production -c CWD"
