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

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

public final class ElasticsearchNodesSniffer implements NodesSniffer {
    //......

    private static Node readNode(String nodeId, JsonParser parser, Scheme scheme) throws IOException {
        HttpHost publishedHost = null;
        /*
         * We sniff the bound hosts so we can look up the node based on any
         * address on which it is listening. This is useful in Elasticsearch's
         * test framework where we sometimes publish ipv6 addresses but the
         * tests contact the node on ipv4.
         */
        Set<HttpHost> boundHosts = new HashSet<>();
        String name = null;
        String version = null;
        /*
         * Multi-valued attributes come with key = `real_key.index` and we
         * unflip them after reading them because we can't rely on the order
         * that they arive.
         */
        final Map<String, String> protoAttributes = new HashMap<String, String>();

        boolean sawRoles = false;
        boolean master = false;
        boolean data = false;
        boolean ingest = false;

        String fieldName = null;
        while (parser.nextToken() != JsonToken.END_OBJECT) {
            if (parser.getCurrentToken() == JsonToken.FIELD_NAME) {
                fieldName = parser.getCurrentName();
            } else if (parser.getCurrentToken() == JsonToken.START_OBJECT) {
                if ("http".equals(fieldName)) {
                    while (parser.nextToken() != JsonToken.END_OBJECT) {
                        if (parser.getCurrentToken() == JsonToken.VALUE_STRING && "publish_address".equals(parser.getCurrentName())) {
                            URI publishAddressAsURI = URI.create(scheme + "://" + parser.getValueAsString());
                            publishedHost = new HttpHost(publishAddressAsURI.getHost(), publishAddressAsURI.getPort(),
                                    publishAddressAsURI.getScheme());
                        } else if (parser.currentToken() == JsonToken.START_ARRAY && "bound_address".equals(parser.getCurrentName())) {
                            while (parser.nextToken() != JsonToken.END_ARRAY) {
                                URI boundAddressAsURI = URI.create(scheme + "://" + parser.getValueAsString());
                                boundHosts.add(new HttpHost(boundAddressAsURI.getHost(), boundAddressAsURI.getPort(),
                                        boundAddressAsURI.getScheme()));
                            }
                        } else if (parser.getCurrentToken() == JsonToken.START_OBJECT) {
                            parser.skipChildren();
                        }
                    }
                } else if ("attributes".equals(fieldName)) {
                    while (parser.nextToken() != JsonToken.END_OBJECT) {
                        if (parser.getCurrentToken() == JsonToken.VALUE_STRING) {
                            String oldValue = protoAttributes.put(parser.getCurrentName(), parser.getValueAsString());
                            if (oldValue != null) {
                                throw new IOException("repeated attribute key [" + parser.getCurrentName() + "]");
                            }
                        } else {
                            parser.skipChildren();
                        }
                    }
                } else {
                    parser.skipChildren();
                }
            } else if (parser.currentToken() == JsonToken.START_ARRAY) {
                if ("roles".equals(fieldName)) {
                    sawRoles = true;
                    while (parser.nextToken() != JsonToken.END_ARRAY) {
                        switch (parser.getText()) {
                        case "master":
                            master = true;
                            break;
                        case "data":
                            data = true;
                            break;
                        case "ingest":
                            ingest = true;
                            break;
                        default:
                            logger.warn("unknown role [" + parser.getText() + "] on node [" + nodeId + "]");
                        }
                    }
                } else {
                    parser.skipChildren();
                }
            } else if (parser.currentToken().isScalarValue()) {
                if ("version".equals(fieldName)) {
                    version = parser.getText();
                } else if ("name".equals(fieldName)) {
                    name = parser.getText();
                }
            }
        }
        //http section is not present if http is not enabled on the node, ignore such nodes
        if (publishedHost == null) {
            logger.debug("skipping node [" + nodeId + "] with http disabled");
            return null;
        }

        Map<String, List<String>> realAttributes = new HashMap<>(protoAttributes.size());
        List<String> keys = new ArrayList<>(protoAttributes.keySet());
        for (String key : keys) {
            if (key.endsWith(".0")) {
                String realKey = key.substring(0, key.length() - 2);
                List<String> values = new ArrayList<>();
                int i = 0;
                while (true) {
                    String value = protoAttributes.remove(realKey + "." + i);
                    if (value == null) {
                        break;
                    }
                    values.add(value);
                    i++;
                }
                realAttributes.put(realKey, unmodifiableList(values));
            }
        }
        for (Map.Entry<String, String> entry : protoAttributes.entrySet()) {
            realAttributes.put(entry.getKey(), singletonList(entry.getValue()));
        }

        if (version.startsWith("2.")) {
            /*
             * 2.x doesn't send roles, instead we try to read them from
             * attributes.
             */
            boolean clientAttribute = v2RoleAttributeValue(realAttributes, "client", false);
            Boolean masterAttribute = v2RoleAttributeValue(realAttributes, "master", null);
            Boolean dataAttribute = v2RoleAttributeValue(realAttributes, "data", null);
            master = masterAttribute == null ? false == clientAttribute : masterAttribute;
            data = dataAttribute == null ? false == clientAttribute : dataAttribute;
        } else {
            assert sawRoles : "didn't see roles for [" + nodeId + "]";
        }
        assert boundHosts.contains(publishedHost) :
                "[" + nodeId + "] doesn't make sense! publishedHost should be in boundHosts";
        logger.trace("adding node [" + nodeId + "]");
        return new Node(publishedHost, boundHosts, name, version, new Roles(master, data, ingest),
                unmodifiableMap(realAttributes));
    }

    /**
     * Returns {@code defaultValue} if the attribute didn't come back,
     * {@code true} or {@code false} if it did come back as
     * either of those, or throws an IOException if the attribute
     * came back in a strange way.
     */
    private static Boolean v2RoleAttributeValue(Map<String, List<String>> attributes,
            String name, Boolean defaultValue) throws IOException {
        List<String> valueList = attributes.remove(name);
        if (valueList == null) {
            return defaultValue;
        }
        if (valueList.size() != 1) {
            throw new IOException("expected only a single attribute value for [" + name + "] but got "
                    + valueList);
        }
        switch (valueList.get(0)) {
        case "true":
            return true;
        case "false":
            return false;
        default:
            throw new IOException("expected [" + name + "] to be either [true] or [false] but was ["
                    + valueList.get(0) + "]");
        }
    }

    //......
}

• readNode方法用于解析nodes部分的数据，它会解析http、attributes、roles、version；然后会对2.x版本的进行特殊处理，最后使用publishedHost、boundHosts、name、version、master、data、ingest、realAttributes构建Node实例并返回

小结

• 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
• readNode方法用于解析nodes部分的数据，它会解析http、attributes、roles、version；然后会对2.x版本的进行特殊处理，最后使用publishedHost、boundHosts、name、version、master、data、ingest、realAttributes构建Node实例并返回

doc

• NodesSniffer