def cancel
      workitem[CANCEL_META] = true
      send_workitem_message
    rescue Exception => e
      Maestro.log.warn "Failed To Send Cancel Message To Server #{e.class} #{e}: #{e.backtrace.join("\n")}"
    ensure
      workitem.delete(CANCEL_META)
    end
def cancel
      workitem[CANCEL_META] = true
      send_workitem_message
    rescue Exception => e
      Maestro.log.warn "Failed To Send Cancel Message To Server #{e.class} #{e}: #{e.backtrace.join("\n")}"
    ensure
      workitem.delete(CANCEL_META)
    end
Send the "cancel" message to the server