（三）elasticsearch 源码之启动流程分析

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.Elasticsearch

public 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() {

            @Override
            public 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.Bootstrap

static 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 installed
        BootstrapInfo.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pidFile
        if (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 jars
            checkLucene();

            // 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
            // setDefaultUncaughtExceptionHandler
            Thread.setDefaultUncaughtExceptionHandler(new ElasticsearchUncaughtExceptionHandler());

            INSTANCE.setup(true, environment);

            try {
                // any secure settings must be read during node construction
                IOUtils.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.Bootstrap

private 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 installed
        initializeProbes();

        if (addShutdownHook) {
            Runtime.getRuntime().addShutdownHook(new Thread() {
                @Override
                public 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 hell
            final Logger logger = LogManager.getLogger(JarHell.class);
            JarHell.checkJarHell(logger::debug);
        } catch (IOException | URISyntaxException e) {
            throw new BootstrapException(e);
        }

        // Log ifconfig output before SecurityManager is installed
        IfConfig.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) {
            @Override
            protected void validateNodeBeforeAcceptingRequests(
                final BootstrapContext context,
                final BoundTransportAddress boundTransportAddress, List<BootstrapCheck> 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.Node

protected Node(
            final Environment environment, Collection<Class<? extends Plugin>> classpathPlugins, boolean forbidPrivateIndexSettings) {
    ...
            // 打印jvm信息
            final JvmInfo jvmInfo = JvmInfo.jvmInfo();
            logger.info(
                "version[{}], pid[{}], build[{}/{}/{}/{}], OS[{}/{}/{}], JVM[{}/{}/{}/{}]",
                Build.CURRENT.getQualifiedVersion(),
                jvmInfo.pid(),
                Build.CURRENT.flavor().displayName(),
                Build.CURRENT.type().displayName(),
                Build.CURRENT.hash(),
                Build.CURRENT.date(),
                Constants.OS_NAME,
                Constants.OS_VERSION,
                Constants.OS_ARCH,
                Constants.JVM_VENDOR,
                Constants.JVM_NAME,
                Constants.JAVA_VERSION,
                Constants.JVM_VERSION);
...
            // 初始化各类服务，以及他们相关的依赖
            this.pluginsService = new PluginsService(tmpSettings, environment.configFile(), environment.modulesFile(),
                environment.pluginsFile(), classpathPlugins);
            final Settings settings = pluginsService.updatedSettings();
            final Set<DiscoveryNodeRole> 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.Bootstrap

private 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.Node

public 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

@Override
    protected 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<String, BoundTransportAddress> 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 clusters
            remoteClusterService.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

@Override
    protected 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);
            }
            ...