log.info("");
   private Coordinator prepare(Execution e) throws Exception   {      String providerName = e.getProviderName();      List executorURLs = new ArrayList();      for(Iterator i = jobs.iterator(); i.hasNext(); )      {         Object o = i.next();         if (o instanceof Job)         {            prepare((Job)o, providerName, executorURLs);         }         else         {            for(Iterator ji = ((JobList)o).iterator(); ji.hasNext(); )            {               prepare((Job)ji.next(), providerName, executorURLs);            }         }      }      Coordinator coordinator = pickCoordinator(executorURLs);      checkExecutors(coordinator, executorURLs);      return coordinator;   }