Contents

CloudCrowd.configure(ENV['CLOUD_CROWD_CONFIG'])

require 'cloud_crowd/worker'

module CloudCrowd
  
  # A CloudCrowd::Daemon, started by the Daemons gem, runs a CloudCrowd::Worker in
  # a loop, continually fetching and processing WorkUnits from the central
  # server. The Daemon backs off and pings central less frequently when there
  # isn't any work to be done, and speeds back up when there is.
  class Daemon
    
    MIN_WAIT        = CloudCrowd.config[:min_worker_wait]
    MAX_WAIT        = CloudCrowd.config[:max_worker_wait]
    WAIT_MULTIPLIER = CloudCrowd.config[:worker_wait_multiplier]
    
    def initialize
      @wait_time = MIN_WAIT
      @worker = Worker.new
      Signal.trap('INT',  'EXIT')
      Signal.trap('KILL', 'EXIT')
      Signal.trap('TERM', 'EXIT')
    end
    
    # Loop forever, fetching WorkUnits.
    # TODO: Workers busy with their work units won't die until the unit has 
    # been finished. This should probably be wrapped in an appropriately lengthy
    # timeout, or should be killable from the outside by terminating the thread.
    # In either case, nasty un-cleaned-up bits might be left behind.
    def run
      loop do
        @worker.fetch_work_unit
        if @worker.has_work?
          @wait_time = MIN_WAIT
          while @worker.has_work?
            @worker.run
            sleep 0.01 # So as to listen for incoming signals.
          end
        else
          @wait_time = [@wait_time * WAIT_MULTIPLIER, MAX_WAIT].min
          sleep @wait_time
        end
      end
    end
    
  end
  
end

CloudCrowd::Daemon.new.run

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
documentcloud-cloud-crowd-0.0.4	lib/cloud_crowd/daemon.rb