/**
  * Returns the alive Nodes accessible by the RM
  *
  * @return list of ProActive Nodes
  */
 public List<Node> listAliveNodes() throws Exception {
   ArrayList<Node> nodes = new ArrayList<>();
   Set<String> urls = getResourceManager().listAliveNodeUrls();
   for (String url : urls) {
     nodes.add(NodeFactory.getNode(url));
   }
   return nodes;
 }