EurekaClient在SpringCloud中的启动分析
1、@EnableDiscoveryClient
1、引入 jar 包就不说了
2、在 Application 启动类上加上@EnableEurekaClient注解
@SpringBootApplication
@EnableEurekaClient//该注解就是让其成为一个 client,去向 EurekaServer发起注册
// @EnableDiscoveryClient 这个注解其实跟上面是一样的效果，
//1、只是呢服务发现有很多种实现方式，eureka 只是其中一种，@EnableEurekaClient只对 Eureka 生效，他是在org.springframework.cloud.netflix.eureka 包下，在spring-cloud-netflix-eureka-client-1.4.4.RELEASE.jar包中
//2、@EnableDiscoveryClient对所有的服务发现都可以用，他在 org.springframework.cloud.client.discovery 包下。在spring-cloud-commons-1.3.3.RELEASE.jar 中
public class ServiceAApplication {
public static void main(String[] args) {
SpringApplication.run(ServiceAApplication.class, args);
}
}
2、EurekaDiscoveryClientConfigServiceAutoConfiguration
// 这里有一个条件判断，说明必须有这个类所以我们来看一下这个类
@ConditionalOnBean({
EurekaDiscoveryClientConfiguration.class })
@ConditionalOnProperty(value = "spring.cloud.config.discovery.enabled", matchIfMissing = false)
public class EurekaDiscoveryClientConfigServiceAutoConfiguration {
@Autowired
private ConfigurableApplicationContext context;
@PostConstruct
public void init() {
if (this.context.getParent() != null) {
if (this.context.getBeanNamesForType(EurekaClient.class).length > 0
&& this.context.getParent()
.getBeanNamesForType(EurekaClient.class).length > 0) {
// If the parent has a EurekaClient as well it should be shutdown, so the
// local one can register accurate instance info
this.context.getParent().getBean(EurekaClient.class).shutdown();
}
}
}
}
2.1 EurekaDiscoveryClientConfiguration
@Configuration
@EnableConfigurationProperties
@ConditionalOnClass(EurekaClientConfig.class)
@ConditionalOnProperty(value = "eureka.client.enabled", matchIfMissing = true)
public class EurekaDiscoveryClientConfiguration {
class Marker {
}
@Bean
public Marker eurekaDiscoverClientMarker() {
return new Marker();
}
@Configuration
@ConditionalOnClass(RefreshScopeRefreshedEvent.class)
protected static class EurekaClientConfigurationRefresher {
@Autowired(required = false)
private EurekaClient eurekaClient;
@Autowired(required = false)
private EurekaAutoServiceRegistration autoRegistration;
@EventListener(RefreshScopeRefreshedEvent.class)
public void onApplicationEvent(RefreshScopeRefreshedEvent event) {
//This will force the creation of the EurkaClient bean if not already created
//to make sure the client will be reregistered after a refresh event
if(eurekaClient != null) {
eurekaClient.getApplications();
}
if (autoRegistration != null) {
// register in case meta data changed
this.autoRegistration.stop();
// 这里有一个 start() 关注一下
this.autoRegistration.start();
}
}
}
@Configuration
@ConditionalOnProperty(value = "eureka.client.healthcheck.enabled", matchIfMissing = false)
protected static class EurekaHealthCheckHandlerConfiguration {
@Autowired(required = false)
private HealthAggregator healthAggregator = new OrderedHealthAggregator();
@Bean
@ConditionalOnMissingBean(HealthCheckHandler.class)
public EurekaHealthCheckHandler eurekaHealthCheckHandler() {
return new EurekaHealthCheckHandler(this.healthAggregator);
}
}
}
2.2 EurekaAutoServiceRegistration
通过打印日志我们会发现，在这个方法中执行了很多逻辑，因为在这个类 start 方法中会触发很多类的构建，比如 DiscoveryClient，他会做很多事情，比如 fetchRegistry、initScheduledTasks()…
public class EurekaAutoServiceRegistration implements AutoServiceRegistration, SmartLifecycle, Ordered {
private static final Log log = LogFactory.getLog(EurekaAutoServiceRegistration.class);
private AtomicBoolean running = new AtomicBoolean(false);
private int order = 0;
private AtomicInteger port = new AtomicInteger(0);
private ApplicationContext context;
private EurekaServiceRegistry serviceRegistry;
private EurekaRegistration registration;
public EurekaAutoServiceRegistration(ApplicationContext context, EurekaServiceRegistry serviceRegistry, EurekaRegistration registration) {
this.context = context;
this.serviceRegistry = serviceRegistry;
this.registration = registration;
}
@Override
public void start() {
System.out.println(LocalDateTime.now() + " " + Thread.currentThread().getName() + " start...");
// only set the port if the nonSecurePort or securePort is 0 and this.port != 0
if (this.port.get() != 0) {
if (this.registration.getNonSecurePort() == 0) {
this.registration.setNonSecurePort(this.port.get());
}
if (this.registration.getSecurePort() == 0 && this.registration.isSecure()) {
this.registration.setSecurePort(this.port.get());
}
}
// only initialize if nonSecurePort is greater than 0 and it isn't already running
// because of containerPortInitializer below
if (!this.running.get() && this.registration.getNonSecurePort() > 0) {
/**
* 1、注册当前客户端(注册的时候可能需要初始化 ApplicationInfoManager、EurekaClient)
*/
/**
* 1>、这个就是下面的打印 before
* 2021-12-19T19:17:34.709 main before register...
* 2>、这个就是 this.serviceRegistry.register(this.registration) 调用这个方法进去的打印信息
* 2021-12-19T19:17:34.709,org.springframework.cloud.netflix.eureka.serviceregistry.EurekaServiceRegistry, enter register()....,reg is:
*
* 3>、实例化 ApplicationInfoManager 准备开始 > 1、创建 InstanceInfo 2、实例化 ApplicationInfoManager
* 1)、2 eurekaApplicationInfoManager
* 2)、2021-12-19 19:17:34.717 INFO 18500 --- [ main] o.s.c.n.eureka.InstanceInfoFactory : Setting initial instance status as: STARTING
* 3)、2021-12-19 19:17:34.717 INFO 18500 --- [ main] c.n.appinfo.ApplicationInfoManager : ApplicationInfoManager constructor ing....
*
* 4>、实例化 CloudEurekaClient(DiscoverClient 的子类)
* 2021-12-19T19:17:34.723,org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration,lazy enter eurekaClient()....
* 2021-12-19 19:17:34.757 INFO 18500 --- [ main] com.netflix.discovery.DiscoveryClient : Initializing Eureka in region us-east-1
* 2021-12-19T19:33:27.243,com.netflix.discovery.DiscoveryClient,enter constructor.... after scheduleServerEndpointTask
* 2021-12-19 19:33:27.250 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Disable delta property : false
* 2021-12-19 19:33:27.250 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Single vip registry refresh property : null
* 2021-12-19 19:33:27.250 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Force full registry fetch : false
* 2021-12-19 19:33:27.250 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Application is null : false
* 2021-12-19 19:33:27.250 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Registered Applications size is zero : true
* 2021-12-19 19:33:27.250 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Application version is -1: true
* 2021-12-19 19:33:27.250 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Getting all instance registry info from the eureka server
* 2021-12-19 19:33:27.384 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : The response status is 200
* 2021-12-19 19:33:27.387 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Starting heartbeat executor: renew interval is: 30
* 2021-12-19 19:33:27.391 INFO 2520 --- [ main] c.n.discovery.InstanceInfoReplicator : InstanceInfoReplicator onDemand update allowed rate per min is 4
* 2021-12-19T19:33:27.391,com.netflix.discovery.DiscoveryClient,添加应用状态变更的监听器....
* 2021-12-19 19:33:27.392 INFO 2520 --- [ main] c.n.discovery.InstanceInfoReplicator : 开启定时任务:2021-12-19T19:33:27.392
* 2021-12-19 19:33:27.394 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Discovery Client initialized at timestamp 1639913607394 with initial instances count: 1
*/
System.out.println(LocalDateTime.now() + " " + Thread.currentThread().getName() + " before register...");
/**
* 5>、进入 EurekaServiceRegistry.register() 方法
* 1、进入打印语句
* 2021-12-19 19:33:27.403 INFO 2520 --- [ main] o.s.c.n.e.s.EurekaServiceRegistry : Registering application ServiceA with eureka with status UP
* 2、实例化上面的那些变量后的状态变更监听事件发布
* 2021-12-19 19:33:27.441 INFO 2520 --- [ main] c.n.appinfo.ApplicationInfoManager : listener:{}, statusChangeEvent:StatusChangeEvent [timestamp=1639913607403, current=UP, previous=STARTING]
* 3、DiscoveryClient 监听到事件的处理
* 2021-12-19 19:33:27.441 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : statusChangeEvent:StatusChangeEvent [timestamp=1639913607403, current=UP, previous=STARTING]
* 2021-12-19 19:33:27.441 INFO 2520 --- [ main] com.netflix.discovery.DiscoveryClient : Saw local status change event StatusChangeEvent [timestamp=1639913607403, current=UP, previous=STARTING]
* 2021-12-19T19:33:27.442 main after register...
* 2021-12-19T19:33:27.442 main before publish InstanceRegisteredEvent...
*/
this.serviceRegistry.register(this.registration);
System.out.println(LocalDateTime.now() + " " + Thread.currentThread().getName() + " after register...");
/**
* 2、发布客户端已注册的事件
*/
System.out.println(LocalDateTime.now() + " " + Thread.currentThread().getName() + " before publish InstanceRegisteredEvent...");
this.context.publishEvent(
new InstanceRegisteredEvent<>(this, this.registration.getInstanceConfig()));
System.out.println(LocalDateTime.now() + " " + Thread.currentThread().getName() + " after publish InstanceRegisteredEvent...");
this.running.set(true);
}
}
@Override
public void stop() {
this.serviceRegistry.deregister(this.registration);
this.running.set(false);
}
@Override
public boolean isRunning() {
return this.running.get();
}
@Override
public int getPhase() {
return 0;
}
@Override
public boolean isAutoStartup() {
return true;
}
@Override
public void stop(Runnable callback) {
stop();
callback.run();
}
@Override
public int getOrder() {
return this.order;
}
@EventListener(EmbeddedServletContainerInitializedEvent.class)
public void onApplicationEvent(EmbeddedServletContainerInitializedEvent event) {
// TODO: take SSL into account when Spring Boot 1.2 is available
int localPort = event.getEmbeddedServletContainer().getPort();
if (this.port.get() == 0) {
log.info("Updating port to " + localPort);
this.port.compareAndSet(0, localPort);
start();
}
}
@EventListener(ContextClosedEvent.class)
public void onApplicationEvent(ContextClosedEvent event) {
if (event.getApplicationContext() == context) {
stop();
}
}
}
3、EurekaClient在SpringCloud中的启动流程 流程图
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