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Defining Workers 

nesquena edited this page · 7 revisions

In Backburner, there are actually many different strategies for processing jobs which are reflected by multiple workers. Custom workers can be defined fairly easily. Simply subclass Backburner::Worker and then define a few key methods for the strategy:

Method Description
prepare Used to prepare the job queues before job processing starts.
start Actual processing strategy based on how jobs are consumed.
process_tube_names Simple way to modify or manage tube names if needed (optional)

Check out the simple worker which is a single-threaded process that processes jobs as simply as possible. You can also check out the forking worker as well as the threads_on_fork worker for more advanced examples. You can also check out the base worker class which can be helpful.

Example

class AlternateWorker < Backburner::Worker
  # Used to prepare job queues before processing jobs.
  # Setup beanstalk tube_names and watch all specified tubes for jobs.
  def prepare
    # Expand tube names with prefix from 'foo' => 'backburner.queues.foo'
    self.tube_names.map! { |name| expand_tube_name(name)  }
    # Log information to logger
    log_info "Working #{tube_names.size} queues: [ #{tube_names.join(', ')} ]"
    # Watch the tubes for processing
    self.connection.tubes.watch!(*self.tube_names)
  end

  # Starts processing new jobs indefinitely.
  # Primary way to consume and process jobs within specified tubes.
  def start
    prepare # Invoke the prepare method defined above
    loop { work_one_job } # Loop over and over processing a job from the tubes
  end

  # Processing the tube names
  # Use to change the way tube names are processed
  # Should at minimum `compact_tube_names` which cleans up the tube_names array
  def process_tube_names(tube_names)
    tubes = compact_tube_names(tube_names)
    # ...extra processing here...
    tubes
  end
end

Helpers

When defining you have access to several existing worker methods, a few key helpers as well as several logging methods. The most notable being:

  • work_one_job - Process a single job from all watched tubes.
  • compact_tube_names - Accepts list of tube_names and normalizes them.
  • tube_names - The list of tube names for this worker to watch.
  • connection - The beanstalkd underlying connection.
  • expand_tube_name - Turns a tube name into a fully qualified tube name with prefix.
  • log_info - Used to log information to specified logger.
  • log_error - Used to log errors to specified logger.

Usage

Once your worker is defined, you can set the worker as the default with:

Backburner.configure do |config|
  config.default_worker = AlternateWorker
end

This will have the worker used by default for all job processing. You can also change the worker explicitly when calling Backburner.work:

Backburner.work('newsletter_sender', :worker => AlternateWorker)
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