   finalize: (params) ->
     throw new Error "Not implemented!"
 
+  ping: ->
+    throw new Error "Not implemented!"
+
   destroy: ->
     throw new Error "Not implemented!"
 

    @worker.postMessage
      message: 'finalize'

  destroy: =>
    @worker.terminate()
    @instance._destroy()

  addQueue: (queue) =>
    @totalSizeQueued += item.size or 0 for item in queue
    @queue = @queue.concat queue
    @nextInQueue()

  nextInQueue: =>
    return if @busy
