@Override
 protected void doClose() throws ElasticsearchException {
   masterFD.close();
   nodesFD.close();
   publishClusterState.close();
   membership.close();
   pingService.close();
 }
 @Override
 protected void doStop() throws ElasticsearchException {
   pingService.stop();
   masterFD.stop("zen disco stop");
   nodesFD.stop();
   initialStateSent.set(false);
   if (sendLeaveRequest) {
     if (!master && latestDiscoNodes.masterNode() != null) {
       try {
         membership.sendLeaveRequestBlocking(
             latestDiscoNodes.masterNode(), localNode, TimeValue.timeValueSeconds(1));
       } catch (Exception e) {
         logger.debug(
             "failed to send leave request to master [{}]", e, latestDiscoNodes.masterNode());
       }
     } else {
       DiscoveryNode[] possibleMasters =
           electMaster.nextPossibleMasters(latestDiscoNodes.nodes().values(), 5);
       for (DiscoveryNode possibleMaster : possibleMasters) {
         if (localNode.equals(possibleMaster)) {
           continue;
         }
         try {
           membership.sendLeaveRequest(latestDiscoNodes.masterNode(), possibleMaster);
         } catch (Exception e) {
           logger.debug(
               "failed to send leave request from master [{}] to possible master [{}]",
               e,
               latestDiscoNodes.masterNode(),
               possibleMaster);
         }
       }
     }
   }
   master = false;
   if (currentJoinThread != null) {
     try {
       currentJoinThread.interrupt();
     } catch (Exception e) {
       // ignore
     }
   }
 }
  @Override
  protected void doStart() throws ElasticsearchException {
    Map<String, String> nodeAttributes = discoveryNodeService.buildAttributes();
    // note, we rely on the fact that its a new id each time we start, see FD and "kill -9" handling
    final String nodeId = getNodeUUID(settings);
    localNode =
        new DiscoveryNode(
            settings.get("name"),
            nodeId,
            transportService.boundAddress().publishAddress(),
            nodeAttributes,
            version);
    latestDiscoNodes =
        new DiscoveryNodes.Builder().put(localNode).localNodeId(localNode.id()).build();
    nodesFD.updateNodes(latestDiscoNodes);
    pingService.start();

    // do the join on a different thread, the DiscoveryService waits for 30s anyhow till it is
    // discovered
    asyncJoinCluster();
  }
  private DiscoveryNode findMaster() {
    ZenPing.PingResponse[] fullPingResponses = pingService.pingAndWait(pingTimeout);
    if (fullPingResponses == null) {
      logger.trace("No full ping responses");
      return null;
    }
    if (logger.isTraceEnabled()) {
      StringBuilder sb = new StringBuilder("full ping responses:");
      if (fullPingResponses.length == 0) {
        sb.append(" {none}");
      } else {
        for (ZenPing.PingResponse pingResponse : fullPingResponses) {
          sb.append("\n\t--> ")
              .append("target [")
              .append(pingResponse.target())
              .append("], master [")
              .append(pingResponse.master())
              .append("]");
        }
      }
      logger.trace(sb.toString());
    }

    // filter responses
    List<ZenPing.PingResponse> pingResponses = Lists.newArrayList();
    for (ZenPing.PingResponse pingResponse : fullPingResponses) {
      DiscoveryNode node = pingResponse.target();
      if (masterElectionFilterClientNodes
          && (node.clientNode() || (!node.masterNode() && !node.dataNode()))) {
        // filter out the client node, which is a client node, or also one that is not data and not
        // master (effectively, client)
      } else if (masterElectionFilterDataNodes && (!node.masterNode() && node.dataNode())) {
        // filter out data node that is not also master
      } else {
        pingResponses.add(pingResponse);
      }
    }

    if (logger.isDebugEnabled()) {
      StringBuilder sb =
          new StringBuilder("filtered ping responses: (filter_client[")
              .append(masterElectionFilterClientNodes)
              .append("], filter_data[")
              .append(masterElectionFilterDataNodes)
              .append("])");
      if (pingResponses.isEmpty()) {
        sb.append(" {none}");
      } else {
        for (ZenPing.PingResponse pingResponse : pingResponses) {
          sb.append("\n\t--> ")
              .append("target [")
              .append(pingResponse.target())
              .append("], master [")
              .append(pingResponse.master())
              .append("]");
        }
      }
      logger.debug(sb.toString());
    }
    List<DiscoveryNode> pingMasters = newArrayList();
    for (ZenPing.PingResponse pingResponse : pingResponses) {
      if (pingResponse.master() != null) {
        pingMasters.add(pingResponse.master());
      }
    }

    Set<DiscoveryNode> possibleMasterNodes = Sets.newHashSet();
    possibleMasterNodes.add(localNode);
    for (ZenPing.PingResponse pingResponse : pingResponses) {
      possibleMasterNodes.add(pingResponse.target());
    }
    // if we don't have enough master nodes, we bail, even if we get a response that indicates
    // there is a master by other node, we don't see enough...
    if (!electMaster.hasEnoughMasterNodes(possibleMasterNodes)) {
      return null;
    }

    if (pingMasters.isEmpty()) {
      // lets tie break between discovered nodes
      DiscoveryNode electedMaster = electMaster.electMaster(possibleMasterNodes);
      if (localNode.equals(electedMaster)) {
        return localNode;
      }
    } else {
      DiscoveryNode electedMaster = electMaster.electMaster(pingMasters);
      if (electedMaster != null) {
        return electedMaster;
      }
    }
    return null;
  }