Eureka - Client服务启动

时间 2021-01-06

标签 spring 缓存 springboot 网络 app dom ide 函数 fetch 栏目 Spring 繁體版

原文原文链接

咱们从下面的图能够看出，做为一个client端，他有如下功能：spring

Register（服务注册）：向Eureka Server注册自身的信息，好比IP地址、端口等。
Renew（服务续约）：服务启动后，每隔30秒会向Eureka Server发送心跳进行服务续约。
Get（服务发现）：获取向Eureka Server注册的服务列表，并缓存本地，默认30秒。
Cancel（服务下线）：向Eureka Server发送下线信息，Eureka Server会把这个服务标志为下线。

服务启动

springboot的自动装配读取Eureka Client的spring.factories文件，咱们看到他里面有多个EnableAutoConfiguration，主要的类是EurekaClientAutoConfiguration。EurekaClientAutoConfiguration类中有多个bean的加载，咱们先看看EurekaInstanceConfigBean的加载。缓存

EurekaInstanceConfigBean

EurekaInstanceConfigBean有个@ConfigurationProperties("eureka.instance")注解，因此咱们在配置文件里写的eureka.instance.instanceId这类的信息最终都在赋值给这个类。还有比较重要的leaseRenewalIntervalInSeconds续约频率（默认每30秒）、leaseExpirationDurationInSeconds续约过时时间（默认90秒）都是在这个类配置的。springboot

@Bean
@ConditionalOnMissingBean(value = EurekaInstanceConfig.class,
        search = SearchStrategy.CURRENT)
public EurekaInstanceConfigBean eurekaInstanceConfigBean(InetUtils inetUtils,
        ManagementMetadataProvider managementMetadataProvider) {
    // 省略部分代码
    EurekaInstanceConfigBean instance = new EurekaInstanceConfigBean(inetUtils);
    // 省略部分代码
    return instance;
}

ApplicationInfoManager

ApplicationInfoManager也是在EurekaClientAutoConfiguration类中。
建立eurekaApplicationInfoManager对象的时候，会先建立InstanceInfo对象，InstanceInfo对象的值大部分是从EurekaInstanceConfig复制过来的，另外租约信息是存放在InstanceInfo的leaseInfo中。
因此初始化ApplicationInfoManager的时候，就是赋值EurekaInstanceConfig和InstanceInfo。网络

@Bean
@ConditionalOnMissingBean(value = ApplicationInfoManager.class,
        search = SearchStrategy.CURRENT)
@org.springframework.cloud.context.config.annotation.RefreshScope
@Lazy
public ApplicationInfoManager eurekaApplicationInfoManager(
        EurekaInstanceConfig config) {
    InstanceInfo instanceInfo = new InstanceInfoFactory().create(config);
    return new ApplicationInfoManager(config, instanceInfo);
}

EurekaClientConfigBean

EurekaClientConfigBean也是一个配置信息的bean，他主要是EurekaClient和EurekaServer相关的信息，好比EurekaServer的地址defaultZone、是否从注册中心拉取注册信息fetchRegistry（默认true），拉取的频率registryFetchIntervalSeconds（默认每30秒）、是否向注册中心注册registerWithEureka（默认true）等。app

@Bean
@ConditionalOnMissingBean(value = EurekaClientConfig.class,
        search = SearchStrategy.CURRENT)
public EurekaClientConfigBean eurekaClientConfigBean(ConfigurableEnvironment env) {
    return new EurekaClientConfigBean();
}

EurekaClient

建立一个EurekaClient类，这个类就是负责服务的注册、续约、取消、获取注册列表。dom

@Bean(destroyMethod = "shutdown")
@ConditionalOnMissingBean(value = EurekaClient.class,
        search = SearchStrategy.CURRENT)
@org.springframework.cloud.context.config.annotation.RefreshScope
@Lazy
public EurekaClient eurekaClient(ApplicationInfoManager manager,
        EurekaClientConfig config, EurekaInstanceConfig instance,
        @Autowired(required = false) HealthCheckHandler healthCheckHandler) {
    ApplicationInfoManager appManager;
    if (AopUtils.isAopProxy(manager)) {
        appManager = ProxyUtils.getTargetObject(manager);
    }
    else {
        appManager = manager;
    }
    CloudEurekaClient cloudEurekaClient = new CloudEurekaClient(appManager,
            config, this.optionalArgs, this.context);
    cloudEurekaClient.registerHealthCheck(healthCheckHandler);
    return cloudEurekaClient;
}

结合上面几个类的加载以及EurekaClient的加载，咱们能够知道这几个类的关系以下：

在DiscoveryClient的构造函数里，主要是初始化一些配置参数，以及为拉取注册表信息、初始化定时任务。ide

@Inject
DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args,
        Provider<BackupRegistry> backupRegistryProvider, EndpointRandomizer endpointRandomizer) {
    // 初始化applicationInfoManager、config等略

    try {
        // 建立核心数为2的线程池，一个用于heartbeat，一个用于cacheRefresh
        // default size of 2 - 1 each for heartbeat and cacheRefresh
        scheduler = Executors.newScheduledThreadPool(2,
                new ThreadFactoryBuilder()
                        .setNameFormat("DiscoveryClient-%d")
                        .setDaemon(true)
                        .build());

        heartbeatExecutor = new ThreadPoolExecutor(
                1, clientConfig.getHeartbeatExecutorThreadPoolSize(), 0, TimeUnit.SECONDS,
                new SynchronousQueue<Runnable>(),
                new ThreadFactoryBuilder()
                        .setNameFormat("DiscoveryClient-HeartbeatExecutor-%d")
                        .setDaemon(true)
                        .build()
        );  // use direct handoff

        cacheRefreshExecutor = new ThreadPoolExecutor(
                1, clientConfig.getCacheRefreshExecutorThreadPoolSize(), 0, TimeUnit.SECONDS,
                new SynchronousQueue<Runnable>(),
                new ThreadFactoryBuilder()
                        .setNameFormat("DiscoveryClient-CacheRefreshExecutor-%d")
                        .setDaemon(true)
                        .build()
        );  // use direct handoff
        // 与EurekaServer网络通讯用的
        eurekaTransport = new EurekaTransport();
        scheduleServerEndpointTask(eurekaTransport, args);
        //其余的略
        
    } catch (Throwable e) {
        throw new RuntimeException("Failed to initialize DiscoveryClient!", e);
    }
    
    if (clientConfig.shouldFetchRegistry()) {
        try {
            // 拉取注册表信息
            boolean primaryFetchRegistryResult = fetchRegistry(false);
            //其余的略，没有拉取成功从备份注册中心获取
        }
    }
    //其余的略
    // 初始化定时任务
    initScheduledTasks();
    //其余的略
}

initScheduledTasks，用来开启更新服务注册列表和续租的定时任务，以及对EurekaServer的注册。函数

private void initScheduledTasks() {
    if (clientConfig.shouldFetchRegistry()) {
        // registry cache refresh timer
        // 这个定时任务是更新服务注册列表
        // 更新频率
        int registryFetchIntervalSeconds = clientConfig.getRegistryFetchIntervalSeconds();
        // 延迟最大乘数，好比更新频率是5s，那最大延迟时间就是50s，这个后面讲线程的时候会具体说
        int expBackOffBound = clientConfig.getCacheRefreshExecutorExponentialBackOffBound();
        cacheRefreshTask = new TimedSupervisorTask(
                "cacheRefresh",
                scheduler,
                cacheRefreshExecutor,
                registryFetchIntervalSeconds,
                TimeUnit.SECONDS,
                expBackOffBound,
                new CacheRefreshThread()
        );
        scheduler.schedule(
                cacheRefreshTask,
                registryFetchIntervalSeconds, TimeUnit.SECONDS);
    }
    instanceInfoReplicator = new InstanceInfoReplicator(
        this,
        instanceInfo,
        clientConfig.getInstanceInfoReplicationIntervalSeconds(),
        2);
    if (clientConfig.shouldRegisterWithEureka()) {
        // 这个定时任务是续租
        // 续约频率
        int renewalIntervalInSecs = instanceInfo.getLeaseInfo().getRenewalIntervalInSecs();
        int expBackOffBound = clientConfig.getHeartbeatExecutorExponentialBackOffBound();
        logger.info("Starting heartbeat executor: " + "renew interval is: {}", renewalIntervalInSecs);

        // Heartbeat timer
        heartbeatTask = new TimedSupervisorTask(
                "heartbeat",
                scheduler,
                heartbeatExecutor,
                renewalIntervalInSecs,
                TimeUnit.SECONDS,
                expBackOffBound,
                new HeartbeatThread()
        );
        scheduler.schedule(
                heartbeatTask,
                renewalIntervalInSecs, TimeUnit.SECONDS);

        // 其余的略
        // 注册到注册中心
        instanceInfoReplicator.start(clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());
    } else {
        logger.info("Not registering with Eureka server per configuration");
    }
}

好了，以上对EurekaServer的注册、续租、注册表获取都说起到了，后面再详细的讲解这些内容。fetch