eureka客户端源码解析

原文：https://blog.tookbra.com/2017/08/25/Spring-Cloud-Eureka-Client-Source/

源码目录结构

.├── pom.xml└── src    ├── main    │   ├── java    │   │   └── org    │   │       └── springframework    │   │           └── cloud    │   │               └── netflix    │   │                   ├── eureka    │   │                   │   ├── CloudEurekaClient.java    │   │                   │   ├── CloudEurekaInstanceConfig.java    │   │                   │   ├── CloudEurekaTransportConfig.java    │   │                   │   ├── EnableEurekaClient.java    │   │                   │   ├── EurekaClientAutoConfiguration.java    │   │                   │   ├── EurekaClientConfigBean.java    │   │                   │   ├── EurekaConstants.java    │   │                   │   ├── EurekaDiscoveryClient.java    │   │                   │   ├── EurekaDiscoveryClientConfiguration.java    │   │                   │   ├── EurekaHealthCheckHandler.java    │   │                   │   ├── EurekaHealthIndicator.java    │   │                   │   ├── EurekaInstanceConfigBean.java    │   │                   │   ├── InstanceInfoFactory.java    │   │                   │   ├── MutableDiscoveryClientOptionalArgs.java    │   │                   │   ├── config    │   │                   │   │   ├── DiscoveryClientOptionalArgsConfiguration.java    │   │                   │   │   ├── EurekaClientConfigServerAutoConfiguration.java    │   │                   │   │   ├── EurekaDiscoveryClientConfigServiceAutoConfiguration.java    │   │                   │   │   └── EurekaDiscoveryClientConfigServiceBootstrapConfiguration.java    │   │                   │   ├── http    │   │                   │   │   ├── EurekaApplications.java    │   │                   │   │   ├── RestTemplateDiscoveryClientOptionalArgs.java    │   │                   │   │   ├── RestTemplateEurekaHttpClient.java    │   │                   │   │   ├── RestTemplateTransportClientFactories.java    │   │                   │   │   └── RestTemplateTransportClientFactory.java    │   │                   │   └── serviceregistry    │   │                   │       ├── EurekaAutoServiceRegistration.java    │   │                   │       ├── EurekaRegistration.java    │   │                   │       └── EurekaServiceRegistry.java    │   │                   └── ribbon    │   │                       └── eureka    │   │                           ├── DomainExtractingServerList.java    │   │                           ├── EurekaRibbonClientConfiguration.java    │   │                           ├── EurekaServerIntrospector.java    │   │                           ├── RibbonEurekaAutoConfiguration.java    │   │                           └── ZoneUtils.java    │   └── resources    │       └── META-INF    │           └── spring.factories    └── test        ├── java        │   └── org        │       └── springframework        │           └── cloud        │               └── netflix        │                   ├── eureka        │                   │   ├── ConditionalOnRefreshScopeTests.java        │                   │   ├── EurekaClientAutoConfigurationTests.java        │                   │   ├── EurekaClientConfigBeanTests.java        │                   │   ├── EurekaHealthCheckHandlerTests.java        │                   │   ├── EurekaInstanceConfigBeanTests.java        │                   │   ├── InstanceInfoFactoryTests.java        │                   │   ├── config        │                   │   │   ├── ConfigRefreshTests.java        │                   │   │   ├── DiscoveryClientConfigServiceAutoConfigurationTests.java        │                   │   │   ├── EurekaClientConfigServerAutoConfigurationTests.java        │                   │   │   ├── JerseyOptionalArgsConfigurationTest.java        │                   │   │   └── RestTemplateOptionalArgsConfigurationTest.java        │                   │   ├── healthcheck        │                   │   │   └── EurekaHealthCheckTests.java        │                   │   ├── http        │                   │   │   ├── EurekaServerMockApplication.java        │                   │   │   ├── RestTemplateEurekaHttpClientTest.java        │                   │   │   ├── RestTemplateTransportClientFactoriesTest.java        │                   │   │   └── RestTemplateTransportClientFactoryTest.java        │                   │   ├── sample        │                   │   │   ├── ApplicationTests.java        │                   │   │   ├── EurekaSampleApplication.java        │                   │   │   └── RefreshEurekaSampleApplication.java        │                   │   └── serviceregistry        │                   │       └── EurekaServiceRegistryTests.java        │                   └── ribbon        │                       └── eureka        │                           ├── DomainExtractingServerListTests.java        │                           ├── EurekaDisabledRibbonClientIntegrationTests.java        │                           ├── EurekaRibbonClientConfigurationTests.java        │                           ├── EurekaRibbonClientPreprocessorIntegrationTests.java        │                           ├── EurekaRibbonClientPropertyOverrideIntegrationTests.java        │                           ├── RibbonClientPreprocessorIntegrationTests.java        │                           ├── RibbonEurekaAutoConfigurationTests.java        │                           └── ZoneUtilsTests.java        └── resources            └── application.yml

客户端启动分析

@SpringBootApplication@EnableDiscoveryClientpublic class ClientApplication {    public static void main(String[] args) {        SpringApplication.run(ClientApplication.class, args);    }}

EnableDiscoveryClient类

@Target({ElementType.TYPE})@Retention(RetentionPolicy.RUNTIME)@Documented@Inherited@Import({EnableDiscoveryClientImportSelector.class})public @interface EnableDiscoveryClient {    boolean autoRegister() default true;}

@Order(Ordered.LOWEST_PRECEDENCE - 100)public class EnableDiscoveryClientImportSelector        extends SpringFactoryImportSelector<EnableDiscoveryClient> {    @Override    public String[] selectImports(AnnotationMetadata metadata) {        String[] imports = super.selectImports(metadata);        AnnotationAttributes attributes = AnnotationAttributes.fromMap(                metadata.getAnnotationAttributes(getAnnotationClass().getName(), true));        boolean autoRegister = attributes.getBoolean("autoRegister");        if (autoRegister) {            List<String> importsList = new ArrayList<>(Arrays.asList(imports));            importsList.add("org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationConfiguration");            imports = importsList.toArray(new String[0]);        }        return imports;    }    ...}

eureka客户端只要在启动类中加上@EnableDiscoveryClient注解，便表示这是一个eureka客户端
在EnableDiscoveryClient类中，可以看到引入了EnableDiscoveryClientImportSelector类
在super.selectImports方法中加载了META-INF目录下有spring.factories文件中的org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\org.springframework.cloud.netflix.eureka.config.EurekaClientConfigServerAutoConfiguration,\org.springframework.cloud.netflix.eureka.config.EurekaDiscoveryClientConfigServiceAutoConfiguration,\org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration,\org.springframework.cloud.netflix.ribbon.eureka.RibbonEurekaAutoConfigurationorg.springframework.cloud.bootstrap.BootstrapConfiguration=\org.springframework.cloud.netflix.eureka.config.EurekaDiscoveryClientConfigServiceBootstrapConfigurationorg.springframework.cloud.client.discovery.EnableDiscoveryClient=\org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration

@Order(2147483547)public class EnableDiscoveryClientImportSelector extends SpringFactoryImportSelector<EnableDiscoveryClient> {    public EnableDiscoveryClientImportSelector() {    }    //返回需要加载的EurekaDiscoveryClientConfiguration bean    public String[] selectImports(AnnotationMetadata metadata) {        //org.springframework.cloud.client.discovery.EnableDiscoveryClient=\org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration        String[] imports = super.selectImports(metadata);        AnnotationAttributes attributes = AnnotationAttributes.fromMap(metadata.getAnnotationAttributes(this.getAnnotationClass().getName(), true));        boolean autoRegister = attributes.getBoolean("autoRegister");        if(autoRegister) {            List<String> importsList = new ArrayList(Arrays.asList(imports));            importsList.add("org.springframework.cloud.client.serviceregistry.AutoServiceRegistrationConfiguration");            imports = (String[])importsList.toArray(new String[0]);        }        return imports;    }    protected boolean isEnabled() {        return ((Boolean)(new RelaxedPropertyResolver(this.getEnvironment())).getProperty("spring.cloud.discovery.enabled", Boolean.class, Boolean.TRUE)).booleanValue();    }    protected boolean hasDefaultFactory() {        return true;    }}

spring-boot在启动过程中通过加载、解析spring.factories文件中的信息，对一些bean进行自动装配，在这里我们就不关注了spring-boot 自动配置
在EurekaServerAutoConfiguration类中

@Configuration@EnableConfigurationProperties@ConditionalOnClass(EurekaClientConfig.class)@ConditionalOnBean(EurekaDiscoveryClientConfiguration.Marker.class)@ConditionalOnProperty(value = "eureka.client.enabled", matchIfMissing = true)@AutoConfigureBefore({ NoopDiscoveryClientAutoConfiguration.class,        CommonsClientAutoConfiguration.class, ServiceRegistryAutoConfiguration.class })@AutoConfigureAfter(name = "org.springframework.cloud.autoconfigure.RefreshAutoConfiguration")public class EurekaClientAutoConfiguration {   ...   @Bean       public DiscoveryClient discoveryClient(EurekaInstanceConfig config,               EurekaClient client) {           return new EurekaDiscoveryClient(config, client);       }       @Configuration    @ConditionalOnRefreshScope    protected static class RefreshableEurekaClientConfiguration {        @Autowired        private ApplicationContext context;        @Autowired(required = false)        private DiscoveryClientOptionalArgs optionalArgs;        @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) {            manager.getInfo(); // force initialization            return new CloudEurekaClient(manager, config, this.optionalArgs,                    this.context);        }        @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);        }    }    @Bean    public DiscoveryClient discoveryClient(EurekaInstanceConfig config,            EurekaClient client) {        return new EurekaDiscoveryClient(config, client);    }   ...}

spring cloud使用CloudEurekaClient对eureka的DiscoveryClient初始化

EurekaAutoServiceRegistration类实现了SmartLifecycle接口的start方法，会在所有spring bean都初始化完成后调用该方法

public class EurekaAutoServiceRegistration implements AutoServiceRegistration, SmartLifecycle, Ordered {    ...    @Override    public void start() {        // only set the port if the nonSecurePort is 0 and this.port != 0        if (this.port.get() != 0 && this.registration.getNonSecurePort() == 0) {            this.registration.setNonSecurePort(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) {            // 设置 eureka 初始化状态 eureka.instance.initial-status            this.serviceRegistry.register(this.registration);            // 传递eureka注册事件            // DiscoveryClientHealthIndicator类监听            this.context.publishEvent(                    new InstanceRegisteredEvent<>(this, this.registration.getInstanceConfig()));            // 设置在spring容器关闭的时候执行stop方法            this.running.set(true);        }    }    ....}

public class EurekaServiceRegistry implements ServiceRegistry<EurekaRegistration> {    public void register(EurekaRegistration reg) {        maybeInitializeClient(reg);        if (log.isInfoEnabled()) {            log.info("Registering application " + reg.getInstanceConfig().getAppname()                    + " with eureka with status "                    + reg.getInstanceConfig().getInitialStatus());        }        reg.getApplicationInfoManager()                .setInstanceStatus(reg.getInstanceConfig().getInitialStatus());        if (reg.getHealthCheckHandler() != null) {            reg.getEurekaClient().registerHealthCheck(reg.getHealthCheckHandler());        }    }}

@Singletonpublic class DiscoveryClient implements EurekaClient {    @Inject    DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args,                    Provider<BackupRegistry> backupRegistryProvider) {        if (args != null) {            this.healthCheckHandlerProvider = args.healthCheckHandlerProvider;            this.healthCheckCallbackProvider = args.healthCheckCallbackProvider;            this.eventListeners.addAll(args.getEventListeners());        } else {            this.healthCheckCallbackProvider = null;            this.healthCheckHandlerProvider = null;        }        this.applicationInfoManager = applicationInfoManager;        //获取 instance        InstanceInfo myInfo = applicationInfoManager.getInfo();        //客户端配置        clientConfig = config;        staticClientConfig = clientConfig;        //传输配置，心跳时间等        transportConfig = config.getTransportConfig();        instanceInfo = myInfo;        if (myInfo != null) {            appPathIdentifier = instanceInfo.getAppName() + "/" + instanceInfo.getId();        } else {            logger.warn("Setting instanceInfo to a passed in null value");        }        this.backupRegistryProvider = backupRegistryProvider;        this.urlRandomizer = new EndpointUtils.InstanceInfoBasedUrlRandomizer(instanceInfo);        localRegionApps.set(new Applications());        fetchRegistryGeneration = new AtomicLong(0);        remoteRegionsToFetch = new AtomicReference<String>(clientConfig.fetchRegistryForRemoteRegions());        remoteRegionsRef = new AtomicReference<>(remoteRegionsToFetch.get() == null ? null : remoteRegionsToFetch.get().split(","));        //是否需要信息检索 eureka.client.fetchRegistry=true        //        if (config.shouldFetchRegistry()) {            this.registryStalenessMonitor = new ThresholdLevelsMetric(this, METRIC_REGISTRY_PREFIX + "lastUpdateSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L});        } else {            this.registryStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC;        }        //是否注册到eureka eureka.client.registerWithEureka=true        if (config.shouldRegisterWithEureka()) {            this.heartbeatStalenessMonitor = new ThresholdLevelsMetric(this, METRIC_REGISTRATION_PREFIX + "lastHeartbeatSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L});        } else {            this.heartbeatStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC;        }        logger.info("Initializing Eureka in region {}", clientConfig.getRegion());        //如果不开启注册到eureka和从eureka检索服务        //把定时任务、心跳设置为null        if (!config.shouldRegisterWithEureka() && !config.shouldFetchRegistry()) {            logger.info("Client configured to neither register nor query for data.");            scheduler = null;            heartbeatExecutor = null;            cacheRefreshExecutor = null;            eurekaTransport = null;            instanceRegionChecker = new InstanceRegionChecker(new PropertyBasedAzToRegionMapper(config), clientConfig.getRegion());            // This is a bit of hack to allow for existing code using DiscoveryManager.getInstance()            // to work with DI'd DiscoveryClient            DiscoveryManager.getInstance().setDiscoveryClient(this);            DiscoveryManager.getInstance().setEurekaClientConfig(config);            initTimestampMs = System.currentTimeMillis();            logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}",                    initTimestampMs, this.getApplications().size());            return;  // no need to setup up an network tasks and we are done        }        // 配置作业        try {            scheduler = Executors.newScheduledThreadPool(3,                    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            eurekaTransport = new EurekaTransport();            scheduleServerEndpointTask(eurekaTransport, args);            AzToRegionMapper azToRegionMapper;            // eureka.client.use-dns-for-fetching-service-urls            if (clientConfig.shouldUseDnsForFetchingServiceUrls()) {                azToRegionMapper = new DNSBasedAzToRegionMapper(clientConfig);            } else {                azToRegionMapper = new PropertyBasedAzToRegionMapper(clientConfig);            }            if (null != remoteRegionsToFetch.get()) {                azToRegionMapper.setRegionsToFetch(remoteRegionsToFetch.get().split(","));            }            instanceRegionChecker = new InstanceRegionChecker(azToRegionMapper, clientConfig.getRegion());        } catch (Throwable e) {            throw new RuntimeException("Failed to initialize DiscoveryClient!", e);        }        //刷新服务注册地址        if (clientConfig.shouldFetchRegistry() && !fetchRegistry(false)) {            fetchRegistryFromBackup();        }        //初始化作业，心跳，状态、缓存        initScheduledTasks();        try {            Monitors.registerObject(this);        } catch (Throwable e) {            logger.warn("Cannot register timers", e);        }        // This is a bit of hack to allow for existing code using DiscoveryManager.getInstance()        // to work with DI'd DiscoveryClient        DiscoveryManager.getInstance().setDiscoveryClient(this);        DiscoveryManager.getInstance().setEurekaClientConfig(config);        initTimestampMs = System.currentTimeMillis();        logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}",                initTimestampMs, this.getApplications().size());    }    /**     * Register with the eureka service by making the appropriate REST call.     */    boolean register() throws Throwable {        logger.info(PREFIX + appPathIdentifier + ": registering service...");        EurekaHttpResponse<Void> httpResponse;        try {            httpResponse = eurekaTransport.registrationClient.register(instanceInfo);        } catch (Exception e) {            logger.warn("{} - registration failed {}", PREFIX + appPathIdentifier, e.getMessage(), e);            throw e;        }        if (logger.isInfoEnabled()) {            logger.info("{} - registration status: {}", PREFIX + appPathIdentifier, httpResponse.getStatusCode());        }        return httpResponse.getStatusCode() == 204;    }}

在DiscoveryClient构造函数中：

• 创建了scheduler定时任务的线程池，heartbeatExecutor心跳检查线程池(服务续约)，cacheRefreshExecutor(服务获取)
• 然后initScheduledTasks()开启上面三个线程池，往上面3个线程池分别添加相应任务。然后创建了一个instanceInfoReplicator(Runnable任务)，然后调用InstanceInfoReplicator.start方法，把这个任务放进上面scheduler定时任务线程池(服务注册并更新)。

public class ApplicationInfoManager {    public synchronized void setInstanceStatus(InstanceStatus status) {        InstanceStatus next = instanceStatusMapper.map(status);        if (next == null) {            return;        }        InstanceStatus prev = instanceInfo.setStatus(next);        if (prev != null) {            for (StatusChangeListener listener : listeners.values()) {                try {                    //状态改变                    listener.notify(new StatusChangeEvent(prev, next));                } catch (Exception e) {                    logger.warn("failed to notify listener: {}", listener.getId(), e);                }            }        }    }}

private void initScheduledTasks() {    if (clientConfig.shouldFetchRegistry()) {        // registry cache refresh timer        int registryFetchIntervalSeconds = clientConfig.getRegistryFetchIntervalSeconds();        int expBackOffBound = clientConfig.getCacheRefreshExecutorExponentialBackOffBound();        scheduler.schedule(                new TimedSupervisorTask(                        "cacheRefresh",                        scheduler,                        cacheRefreshExecutor,                        registryFetchIntervalSeconds,                        TimeUnit.SECONDS,                        expBackOffBound,                        new CacheRefreshThread()                ),                registryFetchIntervalSeconds, TimeUnit.SECONDS);    }    if (clientConfig.shouldRegisterWithEureka()) {        int renewalIntervalInSecs = instanceInfo.getLeaseInfo().getRenewalIntervalInSecs();        int expBackOffBound = clientConfig.getHeartbeatExecutorExponentialBackOffBound();        logger.info("Starting heartbeat executor: " + "renew interval is: " + renewalIntervalInSecs);        // Heartbeat timer        scheduler.schedule(                new TimedSupervisorTask(                        "heartbeat",                        scheduler,                        heartbeatExecutor,                        renewalIntervalInSecs,                        TimeUnit.SECONDS,                        expBackOffBound,                        new HeartbeatThread()                ),                renewalIntervalInSecs, TimeUnit.SECONDS);        // InstanceInfo replicator        instanceInfoReplicator = new InstanceInfoReplicator(                this,                instanceInfo,                clientConfig.getInstanceInfoReplicationIntervalSeconds(),                2); // burstSize        //这里实现了状态改变更新服务        statusChangeListener = new ApplicationInfoManager.StatusChangeListener() {            @Override            public String getId() {                return "statusChangeListener";            }            @Override            public void notify(StatusChangeEvent statusChangeEvent) {                if (InstanceStatus.DOWN == statusChangeEvent.getStatus() ||                        InstanceStatus.DOWN == statusChangeEvent.getPreviousStatus()) {                    // log at warn level if DOWN was involved                    logger.warn("Saw local status change event {}", statusChangeEvent);                } else {                    logger.info("Saw local status change event {}", statusChangeEvent);                }                instanceInfoReplicator.onDemandUpdate();            }        };        //eureka.client.on-demand-update-status-change        //默认为true，一般不设置成false        if (clientConfig.shouldOnDemandUpdateStatusChange()) {            //状态改变监听            applicationInfoManager.registerStatusChangeListener(statusChangeListener);        }        //开启        //初始化实例信息到Eureka服务端的间隔时间 eureka.client.initialInstanceInfoReplicationIntervalSeconds 默认40s        instanceInfoReplicator.start(clientConfig.getInitialInstanceInfoReplicationIntervalSeconds());    } else {        logger.info("Not registering with Eureka server per configuration");    }}