聊聊spring cloud的EurekaServerInitializerConfiguration-白红宇

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本文主要研究一下spring cloud的EurekaServerInitializerConfiguration

EurekaServerInitializerConfiguration

spring-cloud-netflix-eureka-server-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/server/EurekaServerInitializerConfiguration.java

@Configurationpublic class EurekaServerInitializerConfiguration		implements ServletContextAware, SmartLifecycle, Ordered {	//......	@Override	public void start() {		new Thread(new Runnable() {			@Override			public void run() {				try {					//TODO: is this class even needed now?					eurekaServerBootstrap.contextInitialized(EurekaServerInitializerConfiguration.this.servletContext);					log.info("Started Eureka Server");					publish(new EurekaRegistryAvailableEvent(getEurekaServerConfig()));					EurekaServerInitializerConfiguration.this.running = true;					publish(new EurekaServerStartedEvent(getEurekaServerConfig()));				}				catch (Exception ex) {					// Help!					log.error("Could not initialize Eureka servlet context", ex);				}			}		}).start();	}	@Override	public void stop() {		this.running = false;		eurekaServerBootstrap.contextDestroyed(this.servletContext);	}}复制代码

这里start的时候调用了contextInitialized方法，然后stop的时候，调用contextDestroyed

EurekaServerBootstrap.contextInitialized

spring-cloud-netflix-eureka-server-2.0.0.RC1-sources.jar!/org/springframework/cloud/netflix/eureka/server/EurekaServerBootstrap.java

public void contextInitialized(ServletContext context) {		try {			initEurekaEnvironment();			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);		}	}复制代码

这里initEurekaEnvironment初始化环境配置，重点是initEurekaServerContext

EurekaServerBootstrap.initEurekaServerContext

protected void initEurekaServerContext() throws Exception {		// For backward compatibility		JsonXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(),				XStream.PRIORITY_VERY_HIGH);		XmlXStream.getInstance().registerConverter(new V1AwareInstanceInfoConverter(),				XStream.PRIORITY_VERY_HIGH);		if (isAws(this.applicationInfoManager.getInfo())) {			this.awsBinder = new AwsBinderDelegate(this.eurekaServerConfig,					this.eurekaClientConfig, this.registry, this.applicationInfoManager);			this.awsBinder.start();		}		EurekaServerContextHolder.initialize(this.serverContext);		log.info("Initialized server context");		// Copy registry from neighboring eureka node		int registryCount = this.registry.syncUp();		this.registry.openForTraffic(this.applicationInfoManager, registryCount);		// Register all monitoring statistics.		EurekaMonitors.registerAllStats();	}复制代码

这里调用了EurekaServerContextHolder.initialize(this.serverContext)，registry.syncUp()，然后registry.openForTraffic

EurekaServerContextHolder.initialize(this.serverContext)

eureka-core-1.8.8-sources.jar!/com/netflix/eureka/EurekaServerContextHolder.java

/** * A static holder for the server context for use in non-DI cases. * * @author David Liu */public class EurekaServerContextHolder {    private final EurekaServerContext serverContext;    private EurekaServerContextHolder(EurekaServerContext serverContext) {        this.serverContext = serverContext;    }    public EurekaServerContext getServerContext() {        return this.serverContext;    }    private static EurekaServerContextHolder holder;    public static synchronized void initialize(EurekaServerContext serverContext) {        holder = new EurekaServerContextHolder(serverContext);    }    public static EurekaServerContextHolder getInstance() {        return holder;    }}复制代码

主要是给非IOC容器引用EurekaServerContext

syncUp

eureka-core-1.8.8-sources.jar!/com/netflix/eureka/registry/PeerAwareInstanceRegistryImpl.java

/**     * 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.     */    @Override    public int syncUp() {        // Copy entire entry from neighboring DS node        int count = 0;        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();            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;    }复制代码

这里通过client获取其他一个eureka server的实例信息，然后isReplication=true执行instance的注册操作

openForTraffic

Override    public void openForTraffic(ApplicationInfoManager applicationInfoManager, int count) {        // Renewals happen every 30 seconds and for a minute it should be a factor of 2.        this.expectedNumberOfRenewsPerMin = count * 2;        this.numberOfRenewsPerMinThreshold =                (int) (this.expectedNumberOfRenewsPerMin * serverConfig.getRenewalPercentThreshold());        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");        applicationInfoManager.setInstanceStatus(InstanceStatus.UP);        super.postInit();    }复制代码

openForTraffic主要是把自身(eureka server)标识为UP状态，然后可以开始接收请求。

eurekaServerBootstrap.contextDestroyed

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...");	}	/**	 * Server context shutdown hook. Override for custom logic	 */	protected void destroyEurekaServerContext() throws Exception {		EurekaMonitors.shutdown();		if (this.awsBinder != null) {			this.awsBinder.shutdown();		}		if (this.serverContext != null) {			this.serverContext.shutdown();		}	}复制代码

这里销毁上下文和环境变量，注意这里有个this.serverContext != null判断，也就是如果serverContext已经被销毁了，那就不会再调用了。

小结

EurekaServerInitializerConfiguration主要是实现了Lifecycle方法，初始化servlet相关上下文，在start的时候调用EurekaServerBootstrap.contextInitialized，在stop的时候调用eurekaServerBootstrap.contextDestroyed，都是借助eurekaServerBootstrap类来实现。而eurekaServerBootstrap里头部分调用了EurekaServerContext。

EurekaServerBootstrap.contextInitialized这里有两个重要的动作registry.syncUp()以及registry.openForTraffic

registry.syncUp()从其他eureka server获取实例信息，然后注册到本server，然后复制到其他server

registry.openForTraffic()标识自身server的状态为UP，表示可以开始接收请求

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