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