Elasticsearch 8.9启动时构建接收Rest请求的hander过程源码

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一、main方式入口

路径：org.elasticsearch.bootstrap.Elasticsearch

  /*** 启动 elasticsearch 的主入口点。*/public static void main(final String[] args) {Bootstrap bootstrap = initPhase1();assert bootstrap != null;try {initPhase2(bootstrap);initPhase3(bootstrap);} catch (NodeValidationException e) {bootstrap.exitWithNodeValidationException(e);} catch (Throwable t) {bootstrap.exitWithUnknownException(t);}}

这里初始化会有三个初始化阶段。可以直接看initPhase3

二、Elasticsearch初始化第三阶段

 /***初始化的第三阶段*阶段 3 包含初始化安全管理器后的所有内容。到目前为止，该系统一直是单线程的。此阶段可以生成线程、写入日志，并受安全管理器策略的约束。* 在第 3 阶段结束时，系统已准备好接受请求，主线程已准备好终止。这意味着：*    节点组件已构建并启动*    清理已完成（例如安全设置已关闭）*    除主线程外，至少有一个线程处于活动状态，并且在主线程终止后将保持活动状态*    已通知父 CLI 进程系统已准备就绪*/private static void initPhase3(Bootstrap bootstrap) throws IOException, NodeValidationException {//调用checkLucene()函数进行Lucene的检查checkLucene();//创建一个Node对象，并重写validateNodeBeforeAcceptingRequests方法，用于在接受请求之前进行节点验证。Node node = new Node(bootstrap.environment()) {@Overrideprotected void validateNodeBeforeAcceptingRequests(final BootstrapContext context,final BoundTransportAddress boundTransportAddress,List<BootstrapCheck> checks) throws NodeValidationException {BootstrapChecks.check(context, boundTransportAddress, checks);}};//使用bootstrap.spawner()和之前创建的node对象实例化一个Elasticsearch对象，并将其赋值给INSTANCE变量。INSTANCE = new Elasticsearch(bootstrap.spawner(), node);//关闭安全设置IOUtils.close(bootstrap.secureSettings());//启动INSTANCE对象,node会启动，并保持一个存活线程INSTANCE.start();//如果命令行参数指定了daemonize，则移除控制台输出的日志配置。if (bootstrap.args().daemonize()) {LogConfigurator.removeConsoleAppender();}//发送CLI标记，表示服务器已经准备好接受请求。bootstrap.sendCliMarker(BootstrapInfo.SERVER_READY_MARKER);//如果命令行参数指定了daemonize，则关闭流；否则，启动CLI监视线程。if (bootstrap.args().daemonize()) {bootstrap.closeStreams();} else {startCliMonitorThread(System.in);}}

其中INSTANCE.start();如下，代表node启动，并且存活线程运行

private void start() throws NodeValidationException {node.start();keepAliveThread.start();}

1、构造node节点对象时构造restController

public Node(Environment environment) {this(environment, PluginsService.getPluginsServiceCtor(environment), true);}
/*** Constructs a node* 节点的初始化*/protected Node(final Environment initialEnvironment,final Function<Settings, PluginsService> pluginServiceCtor,boolean forbidPrivateIndexSettings) {//省略代码。。。。//里面会初始化restControllerActionModule actionModule = new ActionModule(settings,clusterModule.getIndexNameExpressionResolver(),settingsModule.getIndexScopedSettings(),settingsModule.getClusterSettings(),settingsModule.getSettingsFilter(),threadPool,pluginsService.filterPlugins(ActionPlugin.class),client,circuitBreakerService,usageService,systemIndices,tracer,clusterService,reservedStateHandlers);modules.add(actionModule);//restController存入到networkModule，而NetworkModule是用于处理注册和绑定所有网络相关类的模块//末尾有 actionModule.initRestHandlers初始化handerfinal RestController restController = actionModule.getRestController();final NetworkModule networkModule = new NetworkModule(settings,pluginsService.filterPlugins(NetworkPlugin.class),threadPool,bigArrays,pageCacheRecycler,circuitBreakerService,namedWriteableRegistry,xContentRegistry,networkService,restController,actionModule::copyRequestHeadersToThreadContext,clusterService.getClusterSettings(),tracer);//省略代码。。。。//初始化Rest的HandleractionModule.initRestHandlers(() -> clusterService.state().nodesIfRecovered());}

2、在node构建对象最后执行初始化RestHanders的操作

  public void initRestHandlers(Supplier<DiscoveryNodes> nodesInCluster) {//省略代码。。。这里只选几个经常用到的registerHandler.accept(new RestGetIndicesAction());registerHandler.accept(new RestIndicesStatsAction());registerHandler.accept(new RestCreateIndexAction());    registerHandler.accept(new RestDeleteIndexAction());registerHandler.accept(new RestGetIndexTemplateAction());registerHandler.accept(new RestPutIndexTemplateAction());registerHandler.accept(new RestDeleteIndexTemplateAction());registerHandler.accept(new RestPutMappingAction());registerHandler.accept(new RestGetMappingAction());registerHandler.accept(new RestGetFieldMappingAction());registerHandler.accept(new RestIndexAction());registerHandler.accept(new RestSearchAction(restController.getSearchUsageHolder()));//省略代码}

三、以注册在hander中的RestGetIndicesAction对象为例介绍

/*** The REST handler for get index and head index APIs.* 用于获取索引和头索引 API 的 REST 处理程序。*/
@ServerlessScope(Scope.PUBLIC)
public class RestGetIndicesAction extends BaseRestHandler {//代表路由匹配规则，通过这个规则知道要调用这个实例，每一个实例路由规则都是不一样的@Overridepublic List<Route> routes() {return List.of(new Route(GET, "/{index}"), new Route(HEAD, "/{index}"));}@Overridepublic RestChannelConsumer prepareRequest(final RestRequest request, final NodeClient client) throws IOException {// starting with 7.0 we don't include types by default in the response to GET requestsif (request.getRestApiVersion() == RestApiVersion.V_7&& request.hasParam(INCLUDE_TYPE_NAME_PARAMETER)&& request.method().equals(GET)) {deprecationLogger.compatibleCritical("get_indices_with_types", TYPES_DEPRECATION_MESSAGE);}String[] indices = Strings.splitStringByCommaToArray(request.param("index"));final GetIndexRequest getIndexRequest = new GetIndexRequest();getIndexRequest.indices(indices);getIndexRequest.indicesOptions(IndicesOptions.fromRequest(request, getIndexRequest.indicesOptions()));getIndexRequest.local(request.paramAsBoolean("local", getIndexRequest.local()));getIndexRequest.masterNodeTimeout(request.paramAsTime("master_timeout", getIndexRequest.masterNodeTimeout()));getIndexRequest.humanReadable(request.paramAsBoolean("human", false));getIndexRequest.includeDefaults(request.paramAsBoolean("include_defaults", false));getIndexRequest.features(GetIndexRequest.Feature.fromRequest(request));final var httpChannel = request.getHttpChannel();return channel -> new RestCancellableNodeClient(client, httpChannel).admin().indices().getIndex(getIndexRequest, new RestChunkedToXContentListener<>(channel));}}

1、继承了BaseRestHandler，routes方法做路由规则，父类调用子类的prepareRequest实现

public abstract class BaseRestHandler implements RestHandler {/*** {@inheritDoc}*/@Overridepublic abstract List<Route> routes();@Overridepublic final void handleRequest(RestRequest request, RestChannel channel, NodeClient client) throws Exception {//调用prepareRequest方法，准备请求以供执行，并且会对请求参数进行处理。final RestChannelConsumer action = prepareRequest(request, client);//过滤未使用的参数，将未使用的参数收集到一个有序集合中。final SortedSet<String> unconsumedParams = request.unconsumedParams().stream().filter(p -> responseParams(request.getRestApiVersion()).contains(p) == false).collect(Collectors.toCollection(TreeSet::new));//验证未使用的参数是否有效，如果存在无效参数，则抛出IllegalArgumentException异常。if (unconsumedParams.isEmpty() == false) {final Set<String> candidateParams = new HashSet<>();candidateParams.addAll(request.consumedParams());candidateParams.addAll(responseParams(request.getRestApiVersion()));throw new IllegalArgumentException(unrecognized(request, unconsumedParams, candidateParams, "parameter"));}//验证请求是否包含请求体，并且请求体是否已被消耗，如果不满足条件，则抛出IllegalArgumentException异常。if (request.hasContent() && request.isContentConsumed() == false) {throw new IllegalArgumentException("request [" + request.method() + " " + request.path() + "] does not support having a body");}//增加使用计数usageCount.increment();//执行action，将结果传递给channel。action.accept(channel);}/***准备要执行的请求。* 实现应在返回可运行对象以进行实际执行之前使用所有请求参数。* 未使用的参数将立即终止请求的执行。* 但是，某些参数仅用于处理响应;实现可以覆盖 {@link BaseRestHandlerresponseParams（）} 来指示此类参数。*/protected abstract RestChannelConsumer prepareRequest(RestRequest request, NodeClient client) throws IOException;
}    

2、BaseRestHandler实现的是RestHandler接口

/*** Handler for REST requests*/
@FunctionalInterface
public interface RestHandler {/*** 处理rest请求*/void handleRequest(RestRequest request, RestChannel channel, NodeClient client) throws Exception;/*** 此 RestHandler 负责处理的 {@link 路由} 的列表。*/default List<Route> routes() {return Collections.emptyList();}}

其中调用RestHandler接口的handerRequest的上游是

 @Overridepublic void handleRequest(RestRequest request, RestChannel channel, NodeClient client) throws Exception {//使用 OPTIONS 方法的请求应在其他地方处理，而不是通过调用 {@code RestHandlerhandleRequest} 使用 OPTIONS 方法的 HTTP 请求绕过 authn，因此此健全性检查可防止调度未经身份验证的请求if (request.method() == Method.OPTIONS) {handleException(request,channel,new ElasticsearchSecurityException("Cannot dispatch OPTIONS request, as they are not authenticated"));return;}if (enabled == false) {doHandleRequest(request, channel, client);return;}}private void doHandleRequest(RestRequest request, RestChannel channel, NodeClient client) throws Exception {threadContext.sanitizeHeaders();// operator privileges can short circuit to return a non-successful responseif (operatorPrivilegesService.checkRest(restHandler, request, channel, threadContext)) {try {restHandler.handleRequest(request, channel, client);} catch (Exception e) {logger.debug(() -> format("Request handling failed for REST request [%s]", request.uri()), e);throw e;}}}

其他注册在hander中的API和RestGetIndicesAction类似

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