（三）elasticsearch 源码之启动流程分析

https://www.cnblogs.com/darcy-yuan/p/17007635.html

1.前面我们在《（一）elasticsearch 编译和启动》和 《（二）elasticsearch 源码目录 》简单了解下es（elasticsearch，下同），现在我们来看下启动代码

下面是启动流程图，我们按照流程图的顺序依次描述

2.启动流程

org.elasticsearch.bootstrap.Elasticsearchpublic static void main(final String[] args) throws Exception {overrideDnsCachePolicyProperties();/* * We want the JVM to think there is a security manager installed so that if internal policy decisions that would be based on the * presence of a security manager or lack thereof act as if there is a security manager present (e.g., DNS cache policy). This * forces such policies to take effect immediately. */System.setSecurityManager(new SecurityManager() {@Overridepublic void checkPermission(Permission perm) {// grant all permissions so that we can later set the security manager to the one that we want}});LogConfigurator.registerErrorListener();final Elasticsearch elasticsearch = new Elasticsearch();int status = main(args, elasticsearch, Terminal.DEFAULT);if (status != ExitCodes.OK) {exit(status);}}

后续执行 Elasticsearch.execute -> Elasticsearch.init -> Bootstrap.init

org.elasticsearch.bootstrap.Bootstrapstatic void init(final boolean foreground,final Path pidFile,final boolean quiet,final Environment initialEnv) throws BootstrapException, NodeValidationException, UserException {// force the class initializer for BootstrapInfo to run before// the security manager is installedBootstrapInfo.init();INSTANCE = new Bootstrap();// 安全配置文件final SecureSettings keystore = loadSecureSettings(initialEnv);final Environment environment = createEnvironment(pidFile, keystore, initialEnv.settings(), initialEnv.configFile());LogConfigurator.setNodeName(Node.NODE_NAME_SETTING.get(environment.settings()));try {LogConfigurator.configure(environment);} catch (IOException e) {throw new BootstrapException(e);}if (JavaVersion.current().compareTo(JavaVersion.parse("11")) < 0) {final String message = String.format(Locale.ROOT,"future versions of Elasticsearch will require Java 11; " +"your Java version from [%s] does not meet this requirement",System.getProperty("java.home"));new DeprecationLogger(LogManager.getLogger(Bootstrap.class)).deprecated(message);}// 处理pidFileif (environment.pidFile() != null) {try {PidFile.create(environment.pidFile(), true);} catch (IOException e) {throw new BootstrapException(e);}}// 如果是后台启动，则不打印日志final boolean closeStandardStreams = (foreground == false) || quiet;try {if (closeStandardStreams) {final Logger rootLogger = LogManager.getRootLogger();final Appender maybeConsoleAppender = Loggers.findAppender(rootLogger, ConsoleAppender.class);if (maybeConsoleAppender != null) {Loggers.removeAppender(rootLogger, maybeConsoleAppender);}closeSystOut();}// fail if somebody replaced the lucene jarscheckLucene();// 通用异常捕获// install the default uncaught exception handler; must be done before security is// initialized as we do not want to grant the runtime permission// setDefaultUncaughtExceptionHandlerThread.setDefaultUncaughtExceptionHandler(new ElasticsearchUncaughtExceptionHandler());INSTANCE.setup(true, environment);try {// any secure settings must be read during node constructionIOUtils.close(keystore);} catch (IOException e) {throw new BootstrapException(e);}INSTANCE.start();if (closeStandardStreams) {closeSysError();}}

这里我们可以关注下 INSTANCE.setup(true, environment);

org.elasticsearch.bootstrap.Bootstrapprivate void setup(boolean addShutdownHook, Environment environment) throws BootstrapException {Settings settings = environment.settings();try {spawner.spawnNativeControllers(environment);} catch (IOException e) {throw new BootstrapException(e);}// 检查一些mlock设定initializeNatives(environment.tmpFile(),BootstrapSettings.MEMORY_LOCK_SETTING.get(settings),BootstrapSettings.SYSTEM_CALL_FILTER_SETTING.get(settings),BootstrapSettings.CTRLHANDLER_SETTING.get(settings));// 探针// initialize probes before the security manager is installedinitializeProbes();if (addShutdownHook) {Runtime.getRuntime().addShutdownHook(new Thread() {@Overridepublic void run() {try {IOUtils.close(node, spawner);LoggerContext context = (LoggerContext) LogManager.getContext(false);Configurator.shutdown(context);if (node != null && node.awaitClose(10, TimeUnit.SECONDS) == false) {throw new IllegalStateException("Node didn't stop within 10 seconds. " +"Any outstanding requests or tasks might get killed.");}} catch (IOException ex) {throw new ElasticsearchException("failed to stop node", ex);} catch (InterruptedException e) {LogManager.getLogger(Bootstrap.class).warn("Thread got interrupted while waiting for the node to shutdown.");Thread.currentThread().interrupt();}}});}try {// 检查类加载的一些问题// look for jar hellfinal Logger logger = LogManager.getLogger(JarHell.class);JarHell.checkJarHell(logger::debug);} catch (IOException | URISyntaxException e) {throw new BootstrapException(e);}// Log ifconfig output before SecurityManager is installedIfConfig.logIfNecessary();// 安全处理// install SM after natives, shutdown hooks, etc.try {Security.configure(environment, BootstrapSettings.SECURITY_FILTER_BAD_DEFAULTS_SETTING.get(settings));} catch (IOException | NoSuchAlgorithmException e) {throw new BootstrapException(e);}node = new Node(environment) {@Overrideprotected void validateNodeBeforeAcceptingRequests(final BootstrapContext context,final BoundTransportAddress boundTransportAddress, List checks) throws NodeValidationException {BootstrapChecks.check(context, boundTransportAddress, checks);}};}

最后一句 node = new Node(environment) 初始化了节点，里面做了许多工作

org.elasticsearch.node.Nodeprotected Node(final Environment environment, Collection<Class possibleRoles = Stream.concat(DiscoveryNodeRole.BUILT_IN_ROLES.stream(),pluginsService.filterPlugins(Plugin.class).stream().map(Plugin::getRoles).flatMap(Set::stream)).collect(Collectors.toSet());DiscoveryNode.setPossibleRoles(possibleRoles);localNodeFactory = new LocalNodeFactory(settings, nodeEnvironment.nodeId());...// guice注入modules.add(b -> {b.bind(Node.class).toInstance(this);b.bind(NodeService.class).toInstance(nodeService);b.bind(NamedXContentRegistry.class).toInstance(xContentRegistry);b.bind(PluginsService.class).toInstance(pluginsService);b.bind(Client.class).toInstance(client);b.bind(NodeClient.class).toInstance(client);b.bind(Environment.class).toInstance(this.environment);b.bind(ThreadPool.class).toInstance(threadPool);

es 使用 guice注入框架，guice是个非常轻量级的依赖注入框架，既然各个组件都已经注入好了，我们现在可以启动了。

INSTANCE.start -> Bootstrap.start

org.elasticsearch.bootstrap.Bootstrapprivate void start() throws NodeValidationException {node.start();keepAliveThread.start();}

node.start中启动各个组件。es中的各个组件继承了 AbstractLifecycleComponent。start方法会调用组件的doStart方法。

org.elasticsearch.node.Nodepublic Node start() throws NodeValidationException {if (!lifecycle.moveToStarted()) {return this;}logger.info("starting ...");pluginLifecycleComponents.forEach(LifecycleComponent::start);injector.getInstance(MappingUpdatedAction.class).setClient(client);injector.getInstance(IndicesService.class).start();injector.getInstance(IndicesClusterStateService.class).start();injector.getInstance(SnapshotsService.class).start();injector.getInstance(SnapshotShardsService.class).start();injector.getInstance(SearchService.class).start();nodeService.getMonitorService().start();final ClusterService clusterService = injector.getInstance(ClusterService.class);final NodeConnectionsService nodeConnectionsService = injector.getInstance(NodeConnectionsService.class);nodeConnectionsService.start();clusterService.setNodeConnectionsService(nodeConnectionsService);...

具体的我们看两个比较重要的服务 transportService.start();

org.elasticsearch.transport.TransportService@Overrideprotected void doStart() {transport.setMessageListener(this);connectionManager.addListener(this);// 建立网络连接transport.start();if (transport.boundAddress() != null && logger.isInfoEnabled()) {logger.info("{}", transport.boundAddress());for (Map.Entry entry : transport.profileBoundAddresses().entrySet()) {logger.info("profile [{}]: {}", entry.getKey(), entry.getValue());}}localNode = localNodeFactory.apply(transport.boundAddress());if (connectToRemoteCluster) {// here we start to connect to the remote clustersremoteClusterService.initializeRemoteClusters();}}

启动transport的实现类是 SecurityNetty4HttpServerTransport

另一个比较重要的服务，discovery.start()，具体实现类是 Coordinator

org.elasticsearch.cluster.coordination.Coordinator@Overrideprotected void doStart() {synchronized (mutex) {CoordinationState.PersistedState persistedState = persistedStateSupplier.get();coordinationState.set(new CoordinationState(getLocalNode(), persistedState, electionStrategy));peerFinder.setCurrentTerm(getCurrentTerm());configuredHostsResolver.start();final ClusterState lastAcceptedState = coordinationState.get().getLastAcceptedState();if (lastAcceptedState.metaData().clusterUUIDCommitted()) {logger.info("cluster UUID [{}]", lastAcceptedState.metaData().clusterUUID());}final VotingConfiguration votingConfiguration = lastAcceptedState.getLastCommittedConfiguration();if (singleNodeDiscovery &&votingConfiguration.isEmpty() == false &&votingConfiguration.hasQuorum(Collections.singleton(getLocalNode().getId())) == false) {throw new IllegalStateException("cannot start with [" + DiscoveryModule.DISCOVERY_TYPE_SETTING.getKey() + "] set to [" +DiscoveryModule.SINGLE_NODE_DISCOVERY_TYPE + "] when local node " + getLocalNode() +" does not have quorum in voting configuration " + votingConfiguration);}...