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EurekaServer启动

作者：爱喝兽奶帝天荒 | 2024-07-17 08:34:34

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启动eureka

EurekaServer启动

看方法上的注释，初始化eureka，包含eureka集群的同步和发布注册，这个方法时重写ServletContextListener#contextInitialized，是eureka启动的入口了。在 Servlet 容器( 例如 Tomcat、Jetty )启动时，调用 #contextInitialized() 方法。

  1. /**
  2.      * Initializes Eureka, including syncing up with other Eureka peers and publishing the registry.
  3.      *
  4.      * @see
  5.      * javax.servlet.ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)
  6.      */
  7.     @Override
  8.     public void contextInitialized(ServletContextEvent event) {
  9.         try {
  10.             //初始化eureka环境信息
  11.             initEurekaEnvironment();
  12.             //初始化eureka的上下文
  13.             initEurekaServerContext();
  14.  
  15.             ServletContext sc = event.getServletContext();
  16.             sc.setAttribute(EurekaServerContext.class.getName(), serverContext);
  17.         } catch (Throwable e) {
  18.             logger.error("Cannot bootstrap eureka server :", e);
  19.             throw new RuntimeException("Cannot bootstrap eureka server :", e);
  20.         }
  21.     }

初始化eureka的环境

  1. private static final String TEST = "test";
  2.  
  3.     private static final String ARCHAIUS_DEPLOYMENT_ENVIRONMENT = "archaius.deployment.environment";
  4.  
  5.     private static final String EUREKA_ENVIRONMENT = "eureka.environment";
  6.  
  7.     private static final String CLOUD = "cloud";
  8.     private static final String DEFAULT = "default";
  9.  
  10.     private static final String ARCHAIUS_DEPLOYMENT_DATACENTER = "archaius.deployment.datacenter";
  11.  
  12.     private static final String EUREKA_DATACENTER = "eureka.datacenter";  
  13.  
  14.   protected void initEurekaEnvironment() throws Exception {
  15.         logger.info("Setting the eureka configuration..");
  16.  
  17.         String dataCenter = ConfigurationManager.getConfigInstance().getString(EUREKA_DATACENTER);
  18.         if (dataCenter == null) {
  19.             logger.info("Eureka data center value eureka.datacenter is not set, defaulting to default");
  20.             ConfigurationManager.getConfigInstance().setProperty(ARCHAIUS_DEPLOYMENT_DATACENTER, DEFAULT);
  21.         } else {
  22.             ConfigurationManager.getConfigInstance().setProperty(ARCHAIUS_DEPLOYMENT_DATACENTER, dataCenter);
  23.         }
  24.         String environment = ConfigurationManager.getConfigInstance().getString(EUREKA_ENVIRONMENT);
  25.         if (environment == null) {
  26.             ConfigurationManager.getConfigInstance().setProperty(ARCHAIUS_DEPLOYMENT_ENVIRONMENT, TEST);
  27.             logger.info("Eureka environment value eureka.environment is not set, defaulting to test");
  28.         }
  29.     }

在ConfigurationManager.getConfigInstance()中，其实就是初始化ConfigurationManager的实例

(1)创建一个ConcurrentCompositeConfiguration实例，代表了所谓的配置，包括了eureka需要的所有的配置。在初始化这个实例的时候，调用了clear()方法，fireEvent()发布了一个事件(EVENT_CLEAR)，fireEvent()这个方法其实是父类的方法，牵扯比较复杂的另外一个项目(ConfigurationManager本身不是属于eureka的源码，是属于netflix config项目的源码)。

  1. /**
  2.      * Creates an empty CompositeConfiguration object which can then
  3.      * be added some other Configuration files
  4.      */
  5.     public ConcurrentCompositeConfiguration()
  6.     {
  7.         clear();
  8.     }
  9.  
  10.     @Override
  11.     public final void clear()
  12.     {
  13.         fireEvent(EVENT_CLEAR, null, null, true);
  14.         configList.clear();
  15.         namedConfigurations.clear();
  16.         // recreate the in memory configuration
  17.         containerConfiguration = new ConcurrentMapConfiguration();
  18.         containerConfiguration.setThrowExceptionOnMissing(isThrowExceptionOnMissing());
  19.         containerConfiguration.setListDelimiter(getListDelimiter());
  20.         containerConfiguration.setDelimiterParsingDisabled(isDelimiterParsingDisabled());
  21.         containerConfiguration.addConfigurationListener(eventPropagater);
  22.         configList.add(containerConfiguration);
  23.         
  24.         overrideProperties = new ConcurrentMapConfiguration();
  25.         overrideProperties.setThrowExceptionOnMissing(isThrowExceptionOnMissing());
  26.         overrideProperties.setListDelimiter(getListDelimiter());
  27.         overrideProperties.setDelimiterParsingDisabled(isDelimiterParsingDisabled());
  28.         overrideProperties.addConfigurationListener(eventPropagater);
  29.         
  30.         fireEvent(EVENT_CLEAR, null, null, false);
  31.         containerConfigurationChanged = false;
  32.         invalidate();
  33.     }

(2)就是往上面的那个ConcurrentCompositeConfiguration实例加入了一堆别的config，然后搞完了以后，就直接返回了这个实例，就是作为所谓的那个配置的单例

(3)初始化数据中心的配置，如果没有配置的话，就是DEFAULT data center

(4)初始化eurueka运行的环境，如果你没有配置的话，默认就给你设置为test环境

(5)initEurekaEnvironment的初始化环境的逻辑

初始化eureka的上下文

  1. /**
  2.      * init hook for server context. Override for custom logic.
  3.      */
  4.     protected void initEurekaServerContext() throws Exception {
  5.         //加载eureka-server。properties文件的配置
  6.         EurekaServerConfig eurekaServerConfig = new DefaultEurekaServerConfig();
  7.  
  8.         // For backward compatibility
  9.         JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);
  10.         XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(), XStream.PRIORITY_VERY_HIGH);
  11.  
  12.         logger.info("Initializing the eureka client...");
  13.         logger.info(eurekaServerConfig.getJsonCodecName());
  14.         ServerCodecs serverCodecs = new DefaultServerCodecs(eurekaServerConfig);
  15.  
  16.        //初始化一个ApplicationInfoManager，对应的其实是一个eureka-client。
  17.         ApplicationInfoManager applicationInfoManager = null;
  18.  
  19.         //初始化eureka-server内部的一个eureka-client，用来和其他eureka-server节点用来注册通信的
  20.         if (eurekaClient == null) {
  21.             //CommonConstants. 用来获取client信息
  22.             EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())
  23.                     ? new CloudInstanceConfig()
  24.                     : new MyDataCenterInstanceConfig();
  25.             
  26.             applicationInfoManager = new ApplicationInfoManager(
  27.                     instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());
  28.             
  29.             EurekaClientConfig eurekaClientConfig = new DefaultEurekaClientConfig();
  30.             eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);
  31.         } else {
  32.             applicationInfoManager = eurekaClient.getApplicationInfoManager();
  33.         }
  34.  
  35.         //处理注册的相关事情
  36.         PeerAwareInstanceRegistry registry;
  37.         if (isAws(applicationInfoManager.getInfo())) {
  38.             registry = new AwsInstanceRegistry(
  39.                     eurekaServerConfig,
  40.                     eurekaClient.getEurekaClientConfig(),
  41.                     serverCodecs,
  42.                     eurekaClient
  43.             );
  44.             awsBinder = new AwsBinderDelegate(eurekaServerConfig, eurekaClient.getEurekaClientConfig(), registry, applicationInfoManager);
  45.             awsBinder.start();
  46.         } else {
  47.             registry = new PeerAwareInstanceRegistryImpl(
  48.                     eurekaServerConfig,
  49.                     eurekaClient.getEurekaClientConfig(),
  50.                     serverCodecs,
  51.                     eurekaClient
  52.             );
  53.         }
  54.  
  55.         //处理peer节点
  56.         PeerEurekaNodes peerEurekaNodes = getPeerEurekaNodes(
  57.                 registry,
  58.                 eurekaServerConfig,
  59.                 eurekaClient.getEurekaClientConfig(),
  60.                 serverCodecs,
  61.                 applicationInfoManager
  62.         );
  63.  
  64.         //完成eureka-server上下文的构建以及初始化过程
  65.         serverContext = new DefaultEurekaServerContext(
  66.                 eurekaServerConfig,
  67.                 serverCodecs,
  68.                 registry,
  69.                 peerEurekaNodes,
  70.                 applicationInfoManager
  71.         );
  72.  
  73.         EurekaServerContextHolder.initialize(serverContext);
  74.  
  75.         serverContext.initialize();
  76.         logger.info("Initialized server context");
  77.  
  78.         // 第六步，处理一点善后的事情，从相邻的eureka节点拷贝注册信息
  79.         int registryCount = registry.syncUp();
  80.         //这个方法就是打开注册表，可以接收请求
  81.         registry.openForTraffic(applicationInfoManager, registryCount);
  82.  
  83.         // 注册所有的监控
  84.         EurekaMonitors.registerAllStats();
  85.     }
配置文件读取
  1. public DefaultEurekaServerConfig() {
  2.         init();
  3.     }
  4.  
  5.     private void init() {
  6.         String env = ConfigurationManager.getConfigInstance().getString(
  7.                 EUREKA_ENVIRONMENT, TEST);
  8.         ConfigurationManager.getConfigInstance().setProperty(
  9.                 ARCHAIUS_DEPLOYMENT_ENVIRONMENT, env);
  10.  
  11.         String eurekaPropsFile = EUREKA_PROPS_FILE.get();
  12.         try {
  13.             // ConfigurationManager
  14.             // .loadPropertiesFromResources(eurekaPropsFile);
  15.             ConfigurationManager
  16.                     .loadCascadedPropertiesFromResources(eurekaPropsFile);
  17.         } catch (IOException e) {
  18.             logger.warn(
  19.                     "Cannot find the properties specified : {}. This may be okay if there are other environment "
  20.                             + "specific properties or the configuration is installed with a different mechanism.",
  21.                     eurekaPropsFile);
  22.         }
  23.     }

加载eureka-server.properties的过程：

(1)创建了一个DefaultEurekaServerConfig对象

(2)创建DefaultEurekaServerConfig对象的时候，在里面会有一个init方法

(3)先是将eureka-server.properties中的配置加载到了一个Properties对象中，然后将Properties对象中的配置放到ConfigurationManager中去，此时ConfigurationManager中去就有了所有的配置了

(4)然后DefaultEurekaServerConfig提供的获取配置项的各个方法，都是通过硬编码的配置项名称，从DynamicPropertyFactory中获取配置项的值，DynamicPropertyFactory是从ConfigurationManager那儿来的，所以也包含了所有配置项的值

(5)在获取配置项的时候，如果没有配置，那么就会有默认的值，全部属性都是有默认值的

创建 Eureka-Server 请求和响应编解码器
  1. logger.info("Initializing the eureka client...");
  2. logger.info(eurekaServerConfig.getJsonCodecName());
  3. ServerCodecs serverCodecs = new DefaultServerCodecs(eurekaServerConfig);
创建Eureka-Client
  1. //初始化一个ApplicationInfoManager，对应的其实是一个eureka-client。
  2.         ApplicationInfoManager applicationInfoManager = null;
  3.  
  4.         //初始化eureka-server内部的一个eureka-client，用来和其他eureka-server节点用来注册通信的
  5.         if (eurekaClient == null) {
  6.             //CommonConstants. 用来获取client信息
  7.             EurekaInstanceConfig instanceConfig = isCloud(ConfigurationManager.getDeploymentContext())
  8.                     ? new CloudInstanceConfig()
  9.                     : new MyDataCenterInstanceConfig();
  10.             
  11.             applicationInfoManager = new ApplicationInfoManager(
  12.                     instanceConfig, new EurekaConfigBasedInstanceInfoProvider(instanceConfig).get());
  13.             
  14.             EurekaClientConfig eurekaClientConfig = new DefaultEurekaClientConfig();
  15.             eurekaClient = new DiscoveryClient(applicationInfoManager, eurekaClientConfig);
  16.         } else {
  17.             applicationInfoManager = eurekaClient.getApplicationInfoManager();
  18.         }

在new MyDataCenterInstanceConfig()这个无参构造中，最终会去读取eureka-client.properties的配置，去提供一些默认值。

image-20211008155824162

因为eureka-server本身也是一个eureka-client，因为当组成集群的时候，它自己也要向别的服务端进行注册

  1. //处理注册的相关事情
  2.         PeerAwareInstanceRegistry registry;
  3.         if (isAws(applicationInfoManager.getInfo())) {
  4.             registry = new AwsInstanceRegistry(
  5.                     eurekaServerConfig,
  6.                     eurekaClient.getEurekaClientConfig(),
  7.                     serverCodecs,
  8.                     eurekaClient
  9.             );
  10.             awsBinder = new AwsBinderDelegate(eurekaServerConfig, eurekaClient.getEurekaClientConfig(), registry, applicationInfoManager);
  11.             awsBinder.start();
  12.         } else {
  13.             registry = new PeerAwareInstanceRegistryImpl(
  14.                     eurekaServerConfig,
  15.                     eurekaClient.getEurekaClientConfig(),
  16.                     serverCodecs,
  17.                     eurekaClient
  18.             );
  19.         }
  20.  
  21.         //处理peer节点
  22.         PeerEurekaNodes peerEurekaNodes = getPeerEurekaNodes(
  23.                 registry,
  24.                 eurekaServerConfig,
  25.                 eurekaClient.getEurekaClientConfig(),
  26.                 serverCodecs,
  27.                 applicationInfoManager
  28.         );
  29.  
  30.         //完成eureka-server上下文的构建以及初始化过程
  31.         serverContext = new DefaultEurekaServerContext(
  32.                 eurekaServerConfig,
  33.                 serverCodecs,
  34.                 registry,
  35.                 peerEurekaNodes,
  36.                 applicationInfoManager
  37.         );
初始化 EurekaServerContextHolder
EurekaServerContextHolder.initialize(serverContext);
初始化 Eureka-Server 上下文
  1. @PostConstruct
  2.     @Override
  3.     public void initialize() {
  4.         logger.info("Initializing ...");
  5.         //启动 Eureka-Server 集群节点集合(复制)
  6.         peerEurekaNodes.start();
  7.         try {
  8.             // 初始化 应用实例信息的注册表
  9.             registry.init(peerEurekaNodes);
  10.         } catch (Exception e) {
  11.             throw new RuntimeException(e);
  12.         }
  13.         logger.info("Initialized");
  14.     }
从其他 Eureka-Server 拉取注册信息
  1. // 第六步，处理一点善后的事情，从相邻的eureka节点拷贝注册信息
  2.         int registryCount = registry.syncUp();
  3.         //这个方法就是打开注册表，可以接收请求
  4.         registry.openForTraffic(applicationInfoManager, registryCount);
注册监控
EurekaMonitors.registerAllStats();
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