上一篇介绍了Eureka Server端初始化时的自动装配过程EurekaServerAutoConfiguration ,现在我们来看一下server端的启动源码。
导入启动类
在EurekaServerAutoConfiguration 中，我们看到在自动装配的时候导入了一个类，那就是EurekaServerInitializerConfiguration 这个类就是Eureka Server端的启动调用类。
@import(EurekaServerInitializerConfiguration.class)
在我们分析EurekaServerAutoConfiguration 源码的时候有这个这么一个注册bean。
@Bean
public EurekaServerBootstrap eurekaServerBootstrap(PeerAwareInstanceRegistry registry,
EurekaServerContext serverContext) {
return new EurekaServerBootstrap(this.applicationInfoManager,
this.eurekaClientConfig, this.eurekaServerConfig, registry,
serverContext);
}
这个注册Bean 在导入类中就使用到了。我们来看一下这个类EurekaServerInitializerConfiguration的源码。
@Configuration
public class EurekaServerInitializerConfiguration
implements ServletContextAware, SmartLifecycle, Ordered {
//省略部分源码
@Autowired
private EurekaServerConfig eurekaServerConfig;
private ServletContext servletContext;
@Autowired
private ApplicationContext applicationContext;
@Autowired
private EurekaServerBootstrap eurekaServerBootstrap;
//省略部分源码
//新启动一个线程来启动 eureka Server
@Override
public void start() {
new Thread(new Runnable() {
@Override
public void run() {
try {
//初始化eurekaServer 上下文 并启动 eurekaServer
eurekaServerBootstrap.contextInitialized(
EurekaServerInitializerConfiguration.this.servletContext);
log.info("Started Eureka Server");
//发布可以注册时间
publish(new EurekaRegistryAvailableEvent(getEurekaServerConfig()));
EurekaServerInitializerConfiguration.this.running = true;
//发布启动事件
publish(new EurekaServerStartedEvent(getEurekaServerConfig()));
}
catch (Exception ex) {
// Help!
log.error("Could not initialize Eureka servlet context", ex);
}
}
}).start();
}
//省略部分源码
}
我们可以看到，其实这段源码中没有多少营养的地方，主要就是另启动一个线程，去操作eurekaServerBootstrap的启动类。所以我们需要仔细看一下 eurekaServerBootstrap的源码。
EurekaServerBootstrap
我们截取重要的部分来看一下就可以了。
/**
* @author Spencer Gibb
*/
public class EurekaServerBootstrap {
//省略部分源码
//这里就是 在EurekaServerInitializerConfiguration中调用的启动方法
public void contextInitialized(ServletContext context) {
try {
//初始化 环境参数
initEurekaEnvironment();
//初始化并且配置Eureka 上下文
initEurekaServerContext();
context.setAttribute(EurekaServerContext.class.getName(), this.serverContext);
}
catch (Throwable e) {
log.error("Cannot bootstrap eureka server :", e);
throw new RuntimeException("Cannot bootstrap eureka server :", e);
}
}
//销毁上下文方法
public void contextDestroyed(ServletContext context) {
try {
log.info("Shutting down Eureka Server..");
context.removeAttribute(EurekaServerContext.class.getName());
destroyEurekaServerContext();
destroyEurekaEnvironment();
}
catch (Throwable e) {
log.error("Error shutting down eureka", e);
}
log.info("Eureka Service is now shutdown...");
}
//初始化 环境参数
protected void initEurekaEnvironment() throws Exception {
log.info("Setting the eureka configuration..");
//设置配置文件的数据中心 因为没有学到相关内容，具体作用不知，如果后续
//有学到会更新
String dataCenter = ConfigurationManager.getConfigInstance()
.getString(EUREKA_DATACENTER);
if (dataCenter == null) {
log.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);
}
//获取配置文件的环境变量
String environment = ConfigurationManager.getConfigInstance()
.getString(EUREKA_ENVIRONMENT);
//设置默认的环境变量
if (environment == null) {
ConfigurationManager.getConfigInstance()
.setProperty(ARCHAIUS_DEPLOYMENT_ENVIRONMENT, TEST);
log.info(
"Eureka environment value eureka.environment is not set, defaulting to test");
}
else {
ConfigurationManager.getConfigInstance()
.setProperty(ARCHAIUS_DEPLOYMENT_ENVIRONMENT, environment);
}
}
//初始化上下文
protected void initEurekaServerContext() throws Exception {
// 为了向后兼容，文本转换工具 方便JAVA对象与文本格式数据的相互转换
JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(),
XStream.PRIORITY_VERY_HIGH);
XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(),
XStream.PRIORITY_VERY_HIGH);
//是否是 AWS云服务
if (isAws(this.applicationInfoManager.getInfo())) {
this.awsBinder = new AwsBinderDelegate(this.eurekaServerConfig,
this.eurekaClientConfig, this.registry, this.applicationInfoManager);
this.awsBinder.start();
}
//初始化静态上下文持有
EurekaServerContexHolder.initialize(this.serverContext);
log.info("Initialized server context");
// 从相邻节点copy注册表 具体内容下面有接受
int registryCount = this.registry.syncUp();
//开启注册通道 具体内容下面有解释
this.registry.openForTraffic(this.applicationInfoManager, registryCount);
// 注册Eureka监控的所有统计信息的映射。
EurekaMonitors.registerAllStats();
}
/**
* Server context shutdown hook. Override for custom logic
* @throws Exception - calling {@link AwsBinder#shutdown()} or
* {@link EurekaServerContext#shutdown()} may result in an exception
*/
protected void destroyEurekaServerContext() throws Exception {
EurekaMonitors.shutdown();
if (this.awsBinder != null) {
this.awsBinder.shutdown();
}
if (this.serverContext != null) {
this.serverContext.shutdown();
}
}
/**
* Users can override to clean up the environment themselves.
* @throws Exception - shutting down Eureka servers may result in an exception
*/
protected void destroyEurekaEnvironment() throws Exception {
}
protected boolean isAws(InstanceInfo selfInstanceInfo) {
boolean result = DataCenterInfo.Name.Amazon == selfInstanceInfo
.getDataCenterInfo().getName();
log.info("isAws returned " + result);
return result;
}
}
重点方法补充
this.registry.syncUp()
我们在org.springframework.cloud.netflix.eureka.server.EurekaServerBootstrap#initEurekaServerContext方法中 有一段代码,这段代码的功能是同步注册列表
int registryCount = this.registry.syncUp();
我们来看一下这个方法的源码，如果不知道这个registry注册对象从哪来或者是什么 可以看上一篇内容。这里直接给出类以及方法的具体代码。
com.netflix.eureka.registry.PeerAwareInstanceRegistryImpl#syncUp
/**
* Populates the registry information from a peer eureka node. This
* operation fails over to other nodes until the list is exhausted if the
* communication fails.
*/
//从一个节点获取注册列表填充到本地节点
@Override
public int syncUp() {
// Copy entire entry from neighboring DS node
int count = 0;
//尝试同步一定的次数，如果超过一定的同步次数，则放弃
for (int i = 0; ((i < serverConfig.getRegistrySyncRetries()) && (count == 0)); i++) {
if (i > 0) {
try {
Thread.sleep(serverConfig.getRegistrySyncRetryWaitMs());
} catch (InterruptedException e) {
logger.warn("Interrupted during registry transfer..");
break;
}
}
Applications apps = eurekaClient.getApplications();
//获取注册信息，并同步到本地
for (Application app : apps.getRegisteredApplications()) {
for (InstanceInfo instance : app.getInstances()) {
try {
if (isRegisterable(instance)) {
register(instance, instance.getLeaseInfo().getDurationInSecs(), true);
count++;
}
} catch (Throwable t) {
logger.error("During DS init copy", t);
}
}
}
}
return count;
}
this.registry.openForTraffic(this.applicationInfoManager, registryCount);
我们在org.springframework.cloud.netflix.eureka.server.EurekaServerBootstrap#initEurekaServerContext方法中 有另外一段代码，这段代码的意义是开启注册通道
this.registry.openForTraffic(this.applicationInfoManager, registryCount);
我们来看一下这段方法的源码。
@Override
public void openForTraffic(ApplicationInfoManager applicationInfoManager, int count) {
//同步之后，获取到的注册数据个数
this.expectedNumberOfClientsSendingRenews = count;
// Renewals happen every 30 seconds and for a minute it should be a factor of 2.
//每30秒 重新更新一次
updateRenewsPerMinThreshold();
logger.info("Got {} instances from neighboring DS node", count);
logger.info("Renew threshold is: {}", numberOfRenewsPerMinThreshold);
this.startupTime = System.currentTimeMillis();
if (count > 0) {
this.peerInstancesTransferEmptyOnStartup = false;
}
DataCenterInfo.Name selfName = applicationInfoManager.getInfo().getDataCenterInfo().getName();
boolean isAws = Name.Amazon == selfName;
if (isAws && serverConfig.shouldPrimeAwsReplicaConnections()) {
logger.info("Priming AWS connections for all replicas..");
primeAwsReplicas(applicationInfoManager);
}
logger.info("Changing status to UP");
//设置实例状态，表示已经准备好接收流量，同时通知所有监听该状态的改变事件
applicationInfoManager.setInstanceStatus(InstanceStatus.UP);
super.postInit();
}
总结
Eureka Server 端的启动过程的源码基本已经介绍完了，当然这只是源码的大体介绍，在自动装配过程中，每个Bean的注册，其实都非常有意义去探讨。由于Eureka Server 相关的Bean 是在太多了，真的看不过来。感兴趣的小伙伴可以自行了解一下。
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