Spring中的EurekaServer启动详解
作者：dalianpai
这篇文章主要介绍了Spring中的EurekaServer启动详解,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,需要的朋友可以参考下
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。
/**
* 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环境信息
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的环境
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)。
/**
* 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
/**
* init hook for server context. Override for custom logic.
*/
protected void initEurekaServerContext() throws Exception {
//加载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);
//初始化一个ApplicationInfoManager，对应的其实是一个eureka-client。
ApplicationInfoManager applicationInfoManager = null;
//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
if (eurekaClient == null) {
//CommonConstants. 用来获取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();
}
//处理注册的相关事情
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
);
}
//处理peer节点
PeerEurekaNodes peerEurekaNodes = getPeerEurekaNodes(
registry,
eurekaServerConfig,
eurekaClient.getEurekaClientConfig(),
serverCodecs,
applicationInfoManager
);
//完成eureka-server上下文的构建以及初始化过程
serverContext = new DefaultEurekaServerContext(
eurekaServerConfig,
serverCodecs,
registry,
peerEurekaNodes,
applicationInfoManager
);
EurekaServerContextHolder.initialize(serverContext);
serverContext.initialize();
logger.info("Initialized server context");
// 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
int registryCount = registry.syncUp();
//这个方法就是打开注册表，可以接收请求
registry.openForTraffic(applicationInfoManager, registryCount);
// 注册所有的监控
EurekaMonitors.registerAllStats();
}配置文件读取
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
logger.info("Initializing the eureka client...");
logger.info(eurekaServerConfig.getJsonCodecName());
ServerCodecs serverCodecs = new DefaultServerCodecs(eurekaServerConfig);创建Eureka-Client
//初始化一个ApplicationInfoManager，对应的其实是一个eureka-client。 ApplicationInfoManager applicationInfoManager = null; //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 if (eurekaClient == null) { //CommonConstants. 用来获取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()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。
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
//初始化一个ApplicationInfoManager，对应的其实是一个eureka-client。
ApplicationInfoManager applicationInfoManager = null;
//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
if (eurekaClient == null) {
//CommonConstants. 用来获取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 ...");
//启动 Eureka-Server 集群节点集合(复制)
peerEurekaNodes.start();
try {
// 初始化 应用实例信息的注册表
registry.init(peerEurekaNodes);
} catch (Exception e) {
throw new RuntimeException(e);
}
logger.info("Initialized");
}从其他 Eureka-Server 拉取注册信息
// 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
int registryCount = registry.syncUp();
//这个方法就是打开注册表，可以接收请求
registry.openForTraffic(applicationInfoManager, registryCount);注册监控
EurekaMonitors.registerAllStats();
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