ElasticSearch 问题分析：No data nodes with HTTP-enabled available

环境：ES-5.4.0版本，部署方式：3master node+2client node+3data node

说明：data node和client node都配置了http.enabled: false，程序在写数据时报错：No data nodes with HTTP-enabled available

源码分析：

 public static void filterNonDataNodesIfNeeded(Settings settings, Log log) {
     if (!settings.getNodesDataOnly()) {
         return;
     }

     RestClient bootstrap = new RestClient(settings);
     try  {
         String message = "No data nodes with HTTP-enabled available";
         List<NodeInfo> dataNodes = bootstrap.getHttpDataNodes();
 　　　　// 找不到dataNodes就会报错
         if (dataNodes.isEmpty()) {
             throw new EsHadoopIllegalArgumentException(message);
         }
         ...
     } finally {
         bootstrap.close();
     }
 }

接下来看看RestClient.getHttpDataNodes()方法的取值逻辑

 public List<NodeInfo> getHttpDataNodes() {
     List<NodeInfo> nodes = getHttpNodes(false);
 　　// 遍历上面获取到的节点
     Iterator<NodeInfo> it = nodes.iterator();
     while (it.hasNext()) {
         NodeInfo node = it.next();
 　　　　// 如果不是数据节点，则移除
         if (!node.isData()) {
             it.remove();
         }
     }
     return nodes;
 }

 // 获取http节点_nodes/http
 public List<NodeInfo> getHttpNodes(boolean clientNodeOnly) {
 　　// 通过es接口“_nodes/http”来获取nodes的信息
     Map<String, Map<String, Object>> nodesData = get("_nodes/http", "nodes");
     List<NodeInfo> nodes = new ArrayList<NodeInfo>();

     for (Entry<String, Map<String, Object>> entry : nodesData.entrySet()) {
         NodeInfo node = new NodeInfo(entry.getKey(), entry.getValue());
 　　　　// 如果不是查找client节点，则只要节点运行网络访问就可以add了；如果查找client节点，则还要通过isClient验证才能add
         if (node.hasHttp() && (!clientNodeOnly || node.isClient())) {
             nodes.add(node);
         }
     }
     return nodes;
 }

最后再来看看node.hasHttp()，isClient()，isData()的方法

     private final String id;
     private final String name;
     private final String host;
     private final String ip;
     private final String publishAddress;
     private final boolean hasHttp;
     private final boolean isClient;
     private final boolean isData;
     private final boolean isIngest;

     public NodeInfo(String id, Map<String, Object> map) {
         this.id = id;
         EsMajorVersion version = EsMajorVersion.parse((String) map.get("version"));
         this.name = (String) map.get("name");
         this.host = (String) map.get("host");
         this.ip = (String) map.get("ip");
 　　　　// 5.0以下版本的分支
         if (version.before(EsMajorVersion.V_5_X)) {
             Map<String, Object> attributes = (Map<String, Object>) map.get("attributes");
             if (attributes == null) {
                 this.isClient = false;
                 this.isData = true;
             } else {
                 String data = (String) attributes.get("data");
                 this.isClient = data == null ? true : !Boolean.parseBoolean(data);
                 this.isData = data == null ? true : Boolean.parseBoolean(data);
             }
             this.isIngest = false;
 　　　　// 5.0版本以上的分支
         } else {
             List<String> roles = (List<String>) map.get("roles");
 　　　　　　// 如果roles列表中不包含"data"，则此节点是client
             this.isClient = roles.contains("data") == false;
 　　　　　　// 如果roles列表中包含"data"，则此节点是data
             this.isData = roles.contains("data");
 　　　　　　// 如果roles列表中包含"ingest"，则此节点是ingest
             this.isIngest = roles.contains("ingest");
         }
         Map<String, Object> httpMap = (Map<String, Object>) map.get("http");
 　　　　// 如果节点数据中包含key：http
         if (httpMap != null) {
             String addr = (String) httpMap.get("publish_address");
 　　　　　　// 如果http数据中包含key：publish_address
             if (addr != null) {
                 StringUtils.IpAndPort ipAndPort = StringUtils.parseIpAddress(addr);
                 this.publishAddress = ipAndPort.ip + ":" + ipAndPort.port;
 　　　　　　　　// 则此节点可以提供http服务，即：http.enabled: true
                 this.hasHttp = true;
             } else {
                 this.publishAddress = null;
                 this.hasHttp = false;
             }
         } else {
             this.publishAddress = null;
             this.hasHttp = false;
         }
     }

从上面的源码分析可以得出：如果一个data节点不配置http.enabled：true，则此节点不会被getHttpDataNodes()方法搜索到，那么就会直接抛出异常：No data nodes with HTTP-enabled available

解决的方法无非两种：

第一：数据节点配置 http.enabled：true

第二：绕过filterNonDataNodesIfNeeded()校验，需要settings.getNodesDataOnly()返回false；看下面源码可知，默认es.nodes.data.only是true，在客户端中将其设置为false即可。

 /** Clients only */
 String ES_NODES_CLIENT_ONLY = "es.nodes.client.only";
 String ES_NODES_CLIENT_ONLY_DEFAULT = "false";

 /** Data only */
 String ES_NODES_DATA_ONLY = "es.nodes.data.only";
 String ES_NODES_DATA_ONLY_DEFAULT = "true";

 /** Ingest only */
 String ES_NODES_INGEST_ONLY = "es.nodes.ingest.only";
 String ES_NODES_INGEST_ONLY_DEFAULT = "false";

 /** WAN only */
 String ES_NODES_WAN_ONLY = "es.nodes.wan.only";
 String ES_NODES_WAN_ONLY_DEFAULT = "false";

 ...

 public boolean getNodesDataOnly() {
     // by default, if not set, return a value compatible with the other settings
 　　// 默认es.nodes.data.only是true，在客户端中将其设置为false即可
     return Booleans.parseBoolean(getProperty(ES_NODES_DATA_ONLY), !getNodesWANOnly() && !getNodesClientOnly() && !getNodesIngestOnly());
 }

 public boolean getNodesIngestOnly() {
     return Booleans.parseBoolean(getProperty(ES_NODES_INGEST_ONLY, ES_NODES_INGEST_ONLY_DEFAULT));
 }

 public boolean getNodesClientOnly() {
     return Booleans.parseBoolean(getProperty(ES_NODES_CLIENT_ONLY, ES_NODES_CLIENT_ONLY_DEFAULT));
 }

 public boolean getNodesWANOnly() {
     return Booleans.parseBoolean(getProperty(ES_NODES_WAN_ONLY, ES_NODES_WAN_ONLY_DEFAULT));
 }

最后附上一段"_nodes/http"接口的返回值：

"nodes": {
    "YgwRm4j1RwiK3jjDHY8Hzw": {
      "name": "node-02",
      "transport_address": "192.168.100.10:9300",
      "host": "192.168.100.10",
      "ip": "192.168.100.10",
      "version": "5.4.0",
      "build_hash": "780f8c4",
      "roles": [
        "master",
        "ingest"
      ],
      "attributes": {
        "ml.enabled": "true"
      },
      "http": {
        "bound_address": [
          "192.168.100.10:9200"
        ],
        "publish_address": "192.168.100.10:9200",
        "max_content_length_in_bytes": 104857600
      }
    }
    ...
}