聊聊Elasticsearch的NodesSniffer

序

本文主要研究一下Elasticsearch的NodesSniffer

NodesSniffer

elasticsearch-7.0.1/client/sniffer/src/main/java/org/elasticsearch/client/sniff/NodesSniffer.java

/**
 * Responsible for sniffing the http hosts
 */
public interface NodesSniffer {
    /**
     * Returns the sniffed Elasticsearch nodes.
     */
    List<Node> sniff() throws IOException;
}

NodesSniffer接口定义了sniff方法用于获取sniffed Elasticsearch nodes，它有一个实现类为ElasticsearchNodesSniffer

ElasticsearchNodesSniffer

elasticsearch-7.0.1/client/sniffer/src/main/java/org/elasticsearch/client/sniff/ElasticsearchNodesSniffer.java

public final class ElasticsearchNodesSniffer implements NodesSniffer {

    private static final Log logger = LogFactory.getLog(ElasticsearchNodesSniffer.class);

    public static final long DEFAULT_SNIFF_REQUEST_TIMEOUT = TimeUnit.SECONDS.toMillis(1);

    private final RestClient restClient;
    private final Request request;
    private final Scheme scheme;
    private final JsonFactory jsonFactory = new JsonFactory();

    public ElasticsearchNodesSniffer(RestClient restClient) {
        this(restClient, DEFAULT_SNIFF_REQUEST_TIMEOUT, ElasticsearchNodesSniffer.Scheme.HTTP);
    }

    public ElasticsearchNodesSniffer(RestClient restClient, long sniffRequestTimeoutMillis, Scheme scheme) {
        this.restClient = Objects.requireNonNull(restClient, "restClient cannot be null");
        if (sniffRequestTimeoutMillis < 0) {
            throw new IllegalArgumentException("sniffRequestTimeoutMillis must be greater than 0");
        }
        this.request = new Request("GET", "/_nodes/http");
        request.addParameter("timeout", sniffRequestTimeoutMillis + "ms");
        this.scheme = Objects.requireNonNull(scheme, "scheme cannot be null");
    }

    /**
     * Calls the elasticsearch nodes info api, parses the response and returns all the found http hosts
     */
    @Override
    public List<Node> sniff() throws IOException {
        Response response = restClient.performRequest(request);
        return readHosts(response.getEntity(), scheme, jsonFactory);
    }

    static List<Node> readHosts(HttpEntity entity, Scheme scheme, JsonFactory jsonFactory) throws IOException {
        try (InputStream inputStream = entity.getContent()) {
            JsonParser parser = jsonFactory.createParser(inputStream);
            if (parser.nextToken() != JsonToken.START_OBJECT) {
                throw new IOException("expected data to start with an object");
            }
            List<Node> nodes = new ArrayList<>();
            while (parser.nextToken() != JsonToken.END_OBJECT) {
                if (parser.getCurrentToken() == JsonToken.START_OBJECT) {
                    if ("nodes".equals(parser.getCurrentName())) {
                        while (parser.nextToken() != JsonToken.END_OBJECT) {
                            JsonToken token = parser.nextToken();
                            assert token == JsonToken.START_OBJECT;
                            String nodeId = parser.getCurrentName();
                            Node node = readNode(nodeId, parser, scheme);
                            if (node != null) {
                                nodes.add(node);
                            }
                        }
                    } else {
                        parser.skipChildren();
                    }
                }
            }
            return nodes;
        }
    }

    //......

    public enum Scheme {
        HTTP("http"), HTTPS("https");

        private final String name;

        Scheme(String name) {
            this.name = name;
        }

        @Override
        public String toString() {
            return name;
        }
    }

}

ElasticsearchNodesSniffer的构造器需要restClient、sniffRequestTimeoutMillis、scheme三个参数，其中sniffRequestTimeoutMillis默认为1秒，scheme默认为HTTP；它的构造器创建了GET /_nodes/http的request；sniff方法使用restClient.performRequest来执行这个GET /_nodes/http的request，之后调用readHosts来解析response，其中调用了readNode方法来解析nodes部分

GET /_nodes/http实例

{
  "_nodes" : {
    "total" : 1,
    "successful" : 1,
    "failed" : 0
  },
  "cluster_name" : "docker-cluster",
  "nodes" : {
    "d7w2wdw7Q7SqERe5_fxZYA" : {
      "name" : "d7w2wdw",
      "transport_address" : "172.17.0.2:9300",
      "host" : "172.17.0.2",
      "ip" : "172.17.0.2",
      "version" : "6.6.2",
      "build_flavor" : "oss",
      "build_type" : "tar",
      "build_hash" : "3bd3e59",
      "roles" : [
        "master",
        "data",
        "ingest"
      ],
      "http" : {
        "bound_address" : [
          "0.0.0.0:9200"
        ],
        "publish_address" : "192.168.99.100:9200",
        "max_content_length_in_bytes" : 104857600
      }
    }
  }
}

这里http部分有publish_address信息

readNode