Spring中的EurekaServer啟動(dòng)詳解

更新時(shí)間：2023年11月21日 10:00:41 作者：dalianpai

這篇文章主要介紹了Spring中的EurekaServer啟動(dòng)詳解,初始化eureka,包含eureka集群的同步和發(fā)布注冊(cè),這個(gè)方法時(shí)重寫ServletContextListener#contextInitialized,是eureka啟動(dòng)的入口了,需要的朋友可以參考下

EurekaServer啟動(dòng)

看方法上的注釋，初始化eureka，包含eureka集群的同步和發(fā)布注冊(cè)，這個(gè)方法時(shí)重寫ServletContextListener#contextInitialized，是eureka啟動(dòng)的入口了。

在 Servlet 容器( 例如 Tomcat、Jetty )啟動(dòng)時(shí)，調(diào)用 #contextInitialized() 方法。

/**
     * Initializes Eureka, including syncing up with other Eureka peers and publishing the registry.
     *
     * @see
     * javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
     */
    @Override
    public void contextInitialized(ServletContextEvent event) {
        try {
            //初始化eureka環(huán)境信息
            initEurekaEnvironment();
            //初始化eureka的上下文
            initEurekaServerContext();
 
            ServletContext sc = event.getServletContext();
            sc.setAttribute(EurekaServerContext.class.getName(), serverContext);
        } catch (Throwable e) {
            logger.error("Cannot bootstrap eureka server :", e);
            throw new RuntimeException("Cannot bootstrap eureka server :", e);
        }
    }

初始化eureka的環(huán)境

private static final String TEST = "test";
 
    private static final String ARCHAIUS_DEPLOYMENT_ENVIRONMENT = "archaius.deployment.environment";
 
    private static final String EUREKA_ENVIRONMENT = "eureka.environment";
 
    private static final String CLOUD = "cloud";
    private static final String DEFAULT = "default";
 
    private static final String ARCHAIUS_DEPLOYMENT_DATACENTER = "archaius.deployment.datacenter";
 
    private static final String EUREKA_DATACENTER = "eureka.datacenter";  
 
  protected void initEurekaEnvironment() throws Exception {
        logger.info("Setting the eureka configuration..");
 
        String dataCenter = ConfigurationManager.getConfigInstance().getString(EUREKA_DATACENTER);
        if (dataCenter == null) {
            logger.info("Eureka data center value eureka.datacenter is not set, defaulting to default");
            ConfigurationManager.getConfigInstance().setProperty(ARCHAIUS_DEPLOYMENT_DATACENTER, DEFAULT);
        } else {
            ConfigurationManager.getConfigInstance().setProperty(ARCHAIUS_DEPLOYMENT_DATACENTER, dataCenter);
        }
        String environment = ConfigurationManager.getConfigInstance().getString(EUREKA_ENVIRONMENT);
        if (environment == null) {
            ConfigurationManager.getConfigInstance().setProperty(ARCHAIUS_DEPLOYMENT_ENVIRONMENT, TEST);
            logger.info("Eureka environment value eureka.environment is not set, defaulting to test");
        }
    }

在ConfigurationManager.getConfigInstance()中，其實(shí)就是初始化ConfigurationManager的實(shí)例

(1)創(chuàng)建一個(gè)ConcurrentCompositeConfiguration實(shí)例，代表了所謂的配置，包括了eureka需要的所有的配置。在初始化這個(gè)實(shí)例的時(shí)候，調(diào)用了clear()方法，fireEvent()發(fā)布了一個(gè)事件(EVENT_CLEAR)，fireEvent()這個(gè)方法其實(shí)是父類的方法，牽扯比較復(fù)雜的另外一個(gè)項(xiàng)目(ConfigurationManager本身不是屬于eureka的源碼，是屬于netflix config項(xiàng)目的源碼)。

/**
     * Creates an empty CompositeConfiguration object which can then
     * be added some other Configuration files
     */
    public ConcurrentCompositeConfiguration()
    {
        clear();
    }
 
    @Override
    public final void clear()
    {
        fireEvent(EVENT_CLEAR, null, null, true);
        configList.clear();
        namedConfigurations.clear();
        // recreate the in memory configuration
        containerConfiguration = new ConcurrentMapConfiguration();
        containerConfiguration.setThrowExceptionOnMissing(isThrowExceptionOnMissing());
        containerConfiguration.setListDelimiter(getListDelimiter());
        containerConfiguration.setDelimiterParsingDisabled(isDelimiterParsingDisabled());
        containerConfiguration.addConfigurationListener(eventPropagater);
        configList.add(containerConfiguration);
        
        overrideProperties = new ConcurrentMapConfiguration();
        overrideProperties.setThrowExceptionOnMissing(isThrowExceptionOnMissing());
        overrideProperties.setListDelimiter(getListDelimiter());
        overrideProperties.setDelimiterParsingDisabled(isDelimiterParsingDisabled());
        overrideProperties.addConfigurationListener(eventPropagater);
        
        fireEvent(EVENT_CLEAR, null, null, false);
        containerConfigurationChanged = false;
        invalidate();
    }

(2)就是往上面的那個(gè)ConcurrentCompositeConfiguration實(shí)例加入了一堆別的config，然后搞完了以后，就直接返回了這個(gè)實(shí)例，就是作為所謂的那個(gè)配置的單例

(3)初始化數(shù)據(jù)中心的配置，如果沒(méi)有配置的話，就是DEFAULT data center

(4)初始化eurueka運(yùn)行的環(huán)境，如果你沒(méi)有配置的話，默認(rèn)就給你設(shè)置為test環(huán)境

(5)initEurekaEnvironment的初始化環(huán)境的邏輯

初始化eureka的上下文

/**
     * init hook for server context. Override for custom logic.
     */
    protected void initEurekaServerContext() throws Exception {
        //加載eureka-server。properties文件的配置
        EurekaServerConfig eurekaServerConfig = new DefaultEurekaServerConfig();
 
        // For backward compatibility
        JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);
        XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);
 
        logger.info("Initializing the eureka client...");
        logger.info(eurekaServerConfig.getJsonCodecName());
        ServerCodecs serverCodecs = new DefaultServerCodecs(eurekaServerConfig);
 
       //初始化一個(gè)ApplicationInfoManager，對(duì)應(yīng)的其實(shí)是一個(gè)eureka-client。
        ApplicationInfoManager applicationInfoManager = null;
 
        //初始化eureka-server內(nèi)部的一個(gè)eureka-client，用來(lái)和其他eureka-server節(jié)點(diǎn)用來(lái)注冊(cè)通信的
        if (eurekaClient == null) {
            //CommonConstants. 用來(lái)獲取client信息
            EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())
                    ? new CloudInstanceConfig()
                    : new MyDataCenterInstanceConfig();
            
            applicationInfoManager = new ApplicationInfoManager(
                    instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());
            
            EurekaClientConfig eurekaClientConfig = new DefaultEurekaClientConfig();
            eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);
        } else {
            applicationInfoManager = eurekaClient.getApplicationInfoManager();
        }
 
        //處理注冊(cè)的相關(guān)事情
        PeerAwareInstanceRegistry registry;
        if (isAws(applicationInfoManager.getInfo())) {
            registry = new AwsInstanceRegistry(
                    eurekaServerConfig,
                    eurekaClient.getEurekaClientConfig(),
                    serverCodecs,
                    eurekaClient
            );
            awsBinder = new AwsBinderDelegate(eurekaServerConfig, eurekaClient.getEurekaClientConfig(), registry, applicationInfoManager);
            awsBinder.start();
        } else {
            registry = new PeerAwareInstanceRegistryImpl(
                    eurekaServerConfig,
                    eurekaClient.getEurekaClientConfig(),
                    serverCodecs,
                    eurekaClient
            );
        }
 
        //處理peer節(jié)點(diǎn)
        PeerEurekaNodes peerEurekaNodes = getPeerEurekaNodes(
                registry,
                eurekaServerConfig,
                eurekaClient.getEurekaClientConfig(),
                serverCodecs,
                applicationInfoManager
        );
 
        //完成eureka-server上下文的構(gòu)建以及初始化過(guò)程
        serverContext = new DefaultEurekaServerContext(
                eurekaServerConfig,
                serverCodecs,
                registry,
                peerEurekaNodes,
                applicationInfoManager
        );
 
        EurekaServerContextHolder.initialize(serverContext);
 
        serverContext.initialize();
        logger.info("Initialized server context");
 
        // 第六步，處理一點(diǎn)善后的事情，從相鄰的eureka節(jié)點(diǎn)拷貝注冊(cè)信息
        int registryCount = registry.syncUp();
        //這個(gè)方法就是打開(kāi)注冊(cè)表，可以接收請(qǐng)求
        registry.openForTraffic(applicationInfoManager, registryCount);
 
        // 注冊(cè)所有的監(jiān)控
        EurekaMonitors.registerAllStats();
    }

配置文件讀取

public DefaultEurekaServerConfig() {
        init();
    }
 
    private void init() {
        String env = ConfigurationManager.getConfigInstance().getString(
                EUREKA_ENVIRONMENT, TEST);
        ConfigurationManager.getConfigInstance().setProperty(
                ARCHAIUS_DEPLOYMENT_ENVIRONMENT, env);
 
        String eurekaPropsFile = EUREKA_PROPS_FILE.get();
        try {
            // ConfigurationManager
            // .loadPropertiesFromResources(eurekaPropsFile);
            ConfigurationManager
                    .loadCascadedPropertiesFromResources(eurekaPropsFile);
        } catch (IOException e) {
            logger.warn(
                    "Cannot find the properties specified : {}. This may be okay if there are other environment "
                            + "specific properties or the configuration is installed with a different mechanism.",
                    eurekaPropsFile);
        }
    }

加載eureka-server.properties的過(guò)程

(1)創(chuàng)建了一個(gè)DefaultEurekaServerConfig對(duì)象

(2)創(chuàng)建DefaultEurekaServerConfig對(duì)象的時(shí)候，在里面會(huì)有一個(gè)init方法

(3)先是將eureka-server.properties中的配置加載到了一個(gè)Properties對(duì)象中，然后將Properties對(duì)象中的配置放到ConfigurationManager中去，此時(shí)ConfigurationManager中去就有了所有的配置了

(4)然后DefaultEurekaServerConfig提供的獲取配置項(xiàng)的各個(gè)方法，都是通過(guò)硬編碼的配置項(xiàng)名稱，從DynamicPropertyFactory中獲取配置項(xiàng)的值，DynamicPropertyFactory是從ConfigurationManager那兒來(lái)的，所以也包含了所有配置項(xiàng)的值

(5)在獲取配置項(xiàng)的時(shí)候，如果沒(méi)有配置，那么就會(huì)有默認(rèn)的值，全部屬性都是有默認(rèn)值的

創(chuàng)建 Eureka-Server 請(qǐng)求和響應(yīng)編解碼器

logger.info("Initializing the eureka client...");
logger.info(eurekaServerConfig.getJsonCodecName());
ServerCodecs serverCodecs = new DefaultServerCodecs(eurekaServerConfig);

創(chuàng)建Eureka-Client

//初始化一個(gè)ApplicationInfoManager，對(duì)應(yīng)的其實(shí)是一個(gè)eureka-client。        ApplicationInfoManager applicationInfoManager = null;        //初始化eureka-server內(nèi)部的一個(gè)eureka-client，用來(lái)和其他eureka-server節(jié)點(diǎn)用來(lái)注冊(cè)通信的        if (eurekaClient == null) {            //CommonConstants. 用來(lái)獲取client信息            EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())                    ? new CloudInstanceConfig()                    : new MyDataCenterInstanceConfig();                        applicationInfoManager = new ApplicationInfoManager(                    instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());                        EurekaClientConfig eurekaClientConfig = new DefaultEurekaClientConfig();            eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);        } else {            applicationInfoManager = eurekaClient.getApplicationInfoManager();        }

在new MyDataCenterInstanceConfig()這個(gè)無(wú)參構(gòu)造中，最終會(huì)去讀取eureka-client.properties的配置，去提供一些默認(rèn)值。

因?yàn)閑ureka-server本身也是一個(gè)eureka-client，因?yàn)楫?dāng)組成集群的時(shí)候，它自己也要向別的服務(wù)端進(jìn)行注冊(cè)

//初始化一個(gè)ApplicationInfoManager，對(duì)應(yīng)的其實(shí)是一個(gè)eureka-client。
        ApplicationInfoManager applicationInfoManager = null;
 
        //初始化eureka-server內(nèi)部的一個(gè)eureka-client，用來(lái)和其他eureka-server節(jié)點(diǎn)用來(lái)注冊(cè)通信的
        if (eurekaClient == null) {
            //CommonConstants. 用來(lái)獲取client信息
            EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())
                    ? new CloudInstanceConfig()
                    : new MyDataCenterInstanceConfig();
            
            applicationInfoManager = new ApplicationInfoManager(
                    instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());
            
            EurekaClientConfig eurekaClientConfig = new DefaultEurekaClientConfig();
            eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);
        } else {
            applicationInfoManager = eurekaClient.getApplicationInfoManager();
        }

初始化 EurekaServerContextHolder

EurekaServerContextHolder.initialize(serverContext);

初始化 Eureka-Server 上下文

@PostConstruct
    @Override
    public void initialize() {
        logger.info("Initializing ...");
        //啟動(dòng) Eureka-Server 集群節(jié)點(diǎn)集合(復(fù)制)
        peerEurekaNodes.start();
        try {
            // 初始化 應(yīng)用實(shí)例信息的注冊(cè)表
            registry.init(peerEurekaNodes);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        logger.info("Initialized");
    }

從其他 Eureka-Server 拉取注冊(cè)信息

// 第六步，處理一點(diǎn)善后的事情，從相鄰的eureka節(jié)點(diǎn)拷貝注冊(cè)信息
        int registryCount = registry.syncUp();
        //這個(gè)方法就是打開(kāi)注冊(cè)表，可以接收請(qǐng)求
        registry.openForTraffic(applicationInfoManager, registryCount);

注冊(cè)監(jiān)控