EurekaClient 服务注册、发现、续约
经过自己的测试发现客户端不加注解@EnableEurekaClient 也是可以的，这个注解在2.2.1版本中本身也没做任何的处理，如下：
package org.springframework.cloud.netflix.eureka; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Inherited; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; @Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited public @interface EnableEurekaClient { }
而在1.2.6版本中这个注解引入了@EnableDiscoveryClient， 查看如下：
package org.springframework.cloud.netflix.eureka; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Inherited; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import org.springframework.cloud.client.discovery.EnableDiscoveryClient; @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @EnableDiscoveryClient public @interface EnableEurekaClient { }
@EnableDiscoveryClient 通过Import 引入了相关的配置类：
package org.springframework.cloud.client.discovery; import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Inherited; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target; import org.springframework.context.annotation.Import; @Target({ElementType.TYPE}) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @Import({EnableDiscoveryClientImportSelector.class}) public @interface EnableDiscoveryClient { }
所以在2.2.1 版本中，发生作用的不在上面的注解中，而在spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar包中META-INF目录spring.factories文件：
内容如下：
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.RibbonEurekaAutoConfiguration,\ org.springframework.cloud.netflix.eureka.EurekaDiscoveryClientConfiguration,\ org.springframework.cloud.netflix.eureka.reactive.EurekaReactiveDiscoveryClientConfiguration,\ org.springframework.cloud.netflix.eureka.loadbalancer.LoadBalancerEurekaAutoConfiguration org.springframework.cloud.bootstrap.BootstrapConfiguration=\ org.springframework.cloud.netflix.eureka.config.EurekaDiscoveryClientConfigServiceBootstrapConfiguration
上面是自动注入了一堆的自动配置类。EurekaDiscoveryClientConfiguration 就是重点研究的对象。这个类注入了一个Bean
@Bean @ConditionalOnMissingBean public EurekaDiscoveryClient discoveryClient(EurekaClient client, EurekaClientConfig clientConfig) { return new EurekaDiscoveryClient(client, clientConfig); }
可以看出 EurekaClient 也是自动注入的一个bean，在org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration 类中
@Bean(destroyMethod = "shutdown") @ConditionalOnMissingBean(value = EurekaClient.class, search = SearchStrategy.CURRENT) public EurekaClient eurekaClient(ApplicationInfoManager manager, EurekaClientConfig config) { return new CloudEurekaClient(manager, config, this.optionalArgs, this.context); }
接下来从类CloudEurekaClient 开始分析， 构造方法如下：
public CloudEurekaClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs<?> args, ApplicationEventPublisher publisher) { super(applicationInfoManager, config, args); this.applicationInfoManager = applicationInfoManager; this.publisher = publisher; this.eurekaTransportField = ReflectionUtils.findField(DiscoveryClient.class, "eurekaTransport"); ReflectionUtils.makeAccessible(this.eurekaTransportField); }
父类构造如下：com.netflix.discovery.DiscoveryClient#DiscoveryClient(com.netflix.appinfo.ApplicationInfoManager, com.netflix.discovery.EurekaClientConfig, com.netflix.discovery.AbstractDiscoveryClientOptionalArgs)
public DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args) { this(applicationInfoManager, config, args, ResolverUtils::randomize); } public DiscoveryClient(ApplicationInfoManager applicationInfoManager, final EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args, EndpointRandomizer randomizer) { this(applicationInfoManager, config, args, new Provider<BackupRegistry>() { private volatile BackupRegistry backupRegistryInstance; public synchronized BackupRegistry get() { if (this.backupRegistryInstance == null) { String backupRegistryClassName = config.getBackupRegistryImpl(); if (null != backupRegistryClassName) { try { this.backupRegistryInstance = (BackupRegistry)Class.forName(backupRegistryClassName).newInstance(); DiscoveryClient.logger.info("Enabled backup registry of type {}", this.backupRegistryInstance.getClass()); } catch (InstantiationException var3) { DiscoveryClient.logger.error("Error instantiating BackupRegistry.", var3); } catch (IllegalAccessException var4) { DiscoveryClient.logger.error("Error instantiating BackupRegistry.", var4); } catch (ClassNotFoundException var5) { DiscoveryClient.logger.error("Error instantiating BackupRegistry.", var5); } } if (this.backupRegistryInstance == null) { DiscoveryClient.logger.warn("Using default backup registry implementation which does not do anything."); this.backupRegistryInstance = new NotImplementedRegistryImpl(); } } return this.backupRegistryInstance; } }, randomizer); } @Inject DiscoveryClient(ApplicationInfoManager applicationInfoManager, EurekaClientConfig config, AbstractDiscoveryClientOptionalArgs args, Provider<BackupRegistry> backupRegistryProvider, EndpointRandomizer endpointRandomizer) { this.RECONCILE_HASH_CODES_MISMATCH = Monitors.newCounter("DiscoveryClient_ReconcileHashCodeMismatch"); this.FETCH_REGISTRY_TIMER = Monitors.newTimer("DiscoveryClient_FetchRegistry"); this.REREGISTER_COUNTER = Monitors.newCounter("DiscoveryClient_Reregister"); this.localRegionApps = new AtomicReference(); this.fetchRegistryUpdateLock = new ReentrantLock(); this.healthCheckHandlerRef = new AtomicReference(); this.remoteRegionVsApps = new ConcurrentHashMap(); this.lastRemoteInstanceStatus = InstanceStatus.UNKNOWN; this.eventListeners = new CopyOnWriteArraySet(); this.registrySize = 0; this.lastSuccessfulRegistryFetchTimestamp = -1L; this.lastSuccessfulHeartbeatTimestamp = -1L; this.isShutdown = new AtomicBoolean(false); if (args != null) { this.healthCheckHandlerProvider = args.healthCheckHandlerProvider; this.healthCheckCallbackProvider = args.healthCheckCallbackProvider; this.eventListeners.addAll(args.getEventListeners()); this.preRegistrationHandler = args.preRegistrationHandler; } else { this.healthCheckCallbackProvider = null; this.healthCheckHandlerProvider = null; this.preRegistrationHandler = null; } this.applicationInfoManager = applicationInfoManager; InstanceInfo myInfo = applicationInfoManager.getInfo(); this.clientConfig = config; staticClientConfig = this.clientConfig; this.transportConfig = config.getTransportConfig(); this.instanceInfo = myInfo; if (myInfo != null) { this.appPathIdentifier = this.instanceInfo.getAppName() + "/" + this.instanceInfo.getId(); } else { logger.warn("Setting instanceInfo to a passed in null value"); } this.backupRegistryProvider = backupRegistryProvider; this.endpointRandomizer = endpointRandomizer; this.urlRandomizer = new InstanceInfoBasedUrlRandomizer(this.instanceInfo); this.localRegionApps.set(new Applications()); this.fetchRegistryGeneration = new AtomicLong(0L); this.remoteRegionsToFetch = new AtomicReference(this.clientConfig.fetchRegistryForRemoteRegions()); this.remoteRegionsRef = new AtomicReference(this.remoteRegionsToFetch.get() == null ? null : ((String)this.remoteRegionsToFetch.get()).split(",")); if (config.shouldFetchRegistry()) { this.registryStalenessMonitor = new ThresholdLevelsMetric(this, "eurekaClient.registry.lastUpdateSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L}); } else { this.registryStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC; } if (config.shouldRegisterWithEureka()) { this.heartbeatStalenessMonitor = new ThresholdLevelsMetric(this, "eurekaClient.registration.lastHeartbeatSec_", new long[]{15L, 30L, 60L, 120L, 240L, 480L}); } else { this.heartbeatStalenessMonitor = ThresholdLevelsMetric.NO_OP_METRIC; } logger.info("Initializing Eureka in region {}", this.clientConfig.getRegion()); if (!config.shouldRegisterWithEureka() && !config.shouldFetchRegistry()) { logger.info("Client configured to neither register nor query for data."); this.scheduler = null; this.heartbeatExecutor = null; this.cacheRefreshExecutor = null; this.eurekaTransport = null; this.instanceRegionChecker = new InstanceRegionChecker(new PropertyBasedAzToRegionMapper(config), this.clientConfig.getRegion()); DiscoveryManager.getInstance().setDiscoveryClient(this); DiscoveryManager.getInstance().setEurekaClientConfig(config); this.initTimestampMs = System.currentTimeMillis(); logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}", this.initTimestampMs, this.getApplications().size()); } else { try { this.scheduler = Executors.newScheduledThreadPool(2, (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-%d").setDaemon(true).build()); this.heartbeatExecutor = new ThreadPoolExecutor(1, this.clientConfig.getHeartbeatExecutorThreadPoolSize(), 0L, TimeUnit.SECONDS, new SynchronousQueue(), (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-HeartbeatExecutor-%d").setDaemon(true).build()); this.cacheRefreshExecutor = new ThreadPoolExecutor(1, this.clientConfig.getCacheRefreshExecutorThreadPoolSize(), 0L, TimeUnit.SECONDS, new SynchronousQueue(), (new ThreadFactoryBuilder()).setNameFormat("DiscoveryClient-CacheRefreshExecutor-%d").setDaemon(true).build()); this.eurekaTransport = new DiscoveryClient.EurekaTransport(); this.scheduleServerEndpointTask(this.eurekaTransport, args); Object azToRegionMapper; if (this.clientConfig.shouldUseDnsForFetchingServiceUrls()) { azToRegionMapper = new DNSBasedAzToRegionMapper(this.clientConfig); } else { azToRegionMapper = new PropertyBasedAzToRegionMapper(this.clientConfig); } if (null != this.remoteRegionsToFetch.get()) { ((AzToRegionMapper)azToRegionMapper).setRegionsToFetch(((String)this.remoteRegionsToFetch.get()).split(",")); } this.instanceRegionChecker = new InstanceRegionChecker((AzToRegionMapper)azToRegionMapper, this.clientConfig.getRegion()); } catch (Throwable var10) { throw new RuntimeException("Failed to initialize DiscoveryClient!", var10); } if (this.clientConfig.shouldFetchRegistry() && !this.fetchRegistry(false)) { this.fetchRegistryFromBackup(); } if (this.preRegistrationHandler != null) { this.preRegistrationHandler.beforeRegistration(); } if (this.clientConfig.shouldRegisterWithEureka() && this.clientConfig.shouldEnforceRegistrationAtInit()) { try { if (!this.register()) { throw new IllegalStateException("Registration error at startup. Invalid server response."); } } catch (Throwable var9) { logger.error("Registration error at startup: {}", var9.getMessage()); throw new IllegalStateException(var9); } } this.initScheduledTasks(); try { Monitors.registerObject(this); } catch (Throwable var8) { logger.warn("Cannot register timers", var8); } DiscoveryManager.getInstance().setDiscoveryClient(this); DiscoveryManager.getInstance().setEurekaClientConfig(config); this.initTimestampMs = System.currentTimeMillis(); logger.info("Discovery Client initialized at timestamp {} with initial instances count: {}", this.initTimestampMs, this.getApplications().size()); } }
所以重点在最后的构造方法上。接下来从这里开始研究。
上面构造如果不取服务也不注册服务则不做操作，shouldFetchRegistry()、shouldRegisterWithEureka() 就是我们在yml配置的，如下：
org.springframework.cloud.netflix.eureka.EurekaClientConfigBean的方法：
public boolean shouldRegisterWithEureka() { return this.registerWithEureka; } public boolean shouldFetchRegistry() { return this.fetchRegistry; }
try代码块创建了3个线程池：scheduler、 heartbeatExecutor、cacheRefreshExecutor，接下来的操作就是线程池进行的操作。
1. 服务注册
1. 上面方法创建完线程池调用 initScheduledTasks() 方法
com.netflix.discovery.DiscoveryClient#initScheduledTasks
/** * Initializes all scheduled tasks. */ 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 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(); } }; if (clientConfig.shouldOnDemandUpdateStatusChange()) { applicationInfoManager.registerStatusChangeListener(statusChangeListener); } instanceInfoReplicator.start(clientConfig.getInitialInstanceInfoReplicationIntervalSeconds()); } else { logger.info("Not registering with Eureka server per configuration"); } }
2. clientConfig.shouldRegisterWithEureka() 代码块走注册逻辑===下面主要是维持心跳的逻辑
(1) 拿到renewalIntervalInSecs 获取到续约的时间，默认是30s==这里可以看到是通过线程池的scheduler 定时任务
(2) 如下代码块开启维持心跳的代码块：
// Heartbeat timer scheduler.schedule( new TimedSupervisorTask( "heartbeat", scheduler, heartbeatExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new HeartbeatThread() ), renewalIntervalInSecs, TimeUnit.SECONDS);
TimedSupervisorTask 构造如下：
public TimedSupervisorTask(String name, ScheduledExecutorService scheduler, ThreadPoolExecutor executor, int timeout, TimeUnit timeUnit, int expBackOffBound, Runnable task) { this.scheduler = scheduler; this.executor = executor; this.timeoutMillis = timeUnit.toMillis((long)timeout); this.task = task; this.delay = new AtomicLong(this.timeoutMillis); this.maxDelay = this.timeoutMillis * (long)expBackOffBound; this.successCounter = Monitors.newCounter("success"); this.timeoutCounter = Monitors.newCounter("timeouts"); this.rejectedCounter = Monitors.newCounter("rejectedExecutions"); this.throwableCounter = Monitors.newCounter("throwables"); this.threadPoolLevelGauge = new LongGauge(MonitorConfig.builder("threadPoolUsed").build()); Monitors.registerObject(name, this); }
接下来调用 TimedSupervisorTask的run方法： (也就是用线程池跑任务，这里是scheduler里面跑了个ThreadPoolExecutor 线程池异步任务)
public void run() { Future future = null; try { future = this.executor.submit(this.task); this.threadPoolLevelGauge.set((long)this.executor.getActiveCount()); future.get(this.timeoutMillis, TimeUnit.MILLISECONDS); this.delay.set(this.timeoutMillis); this.threadPoolLevelGauge.set((long)this.executor.getActiveCount()); this.successCounter.increment(); } catch (TimeoutException var12) { logger.warn("task supervisor timed out", var12); this.timeoutCounter.increment(); long currentDelay = this.delay.get(); long newDelay = Math.min(this.maxDelay, currentDelay * 2L); this.delay.compareAndSet(currentDelay, newDelay); } catch (RejectedExecutionException var13) { if (!this.executor.isShutdown() && !this.scheduler.isShutdown()) { logger.warn("task supervisor rejected the task", var13); } else { logger.warn("task supervisor shutting down, reject the task", var13); } this.rejectedCounter.increment(); } catch (Throwable var14) { if (!this.executor.isShutdown() && !this.scheduler.isShutdown()) { logger.warn("task supervisor threw an exception", var14); } else { logger.warn("task supervisor shutting down, can't accept the task"); } this.throwableCounter.increment(); } finally { if (future != null) { future.cancel(true); } if (!this.scheduler.isShutdown()) { this.scheduler.schedule(this, this.delay.get(), TimeUnit.MILLISECONDS); } } }
run方法，会跑构造传进来的心跳线程心跳线程如下：com.netflix.discovery.DiscoveryClient.HeartbeatThread
/** * The heartbeat task that renews the lease in the given intervals. */ private class HeartbeatThread implements Runnable { public void run() { if (renew()) { lastSuccessfulHeartbeatTimestamp = System.currentTimeMillis(); } } }
(3) 接下来调用com.netflix.discovery.DiscoveryClient#renew
/** * Renew with the eureka service by making the appropriate REST call */ boolean renew() { EurekaHttpResponse<InstanceInfo> httpResponse; try { httpResponse = eurekaTransport.registrationClient.sendHeartBeat(instanceInfo.getAppName(), instanceInfo.getId(), instanceInfo, null); logger.debug(PREFIX + "{} - Heartbeat status: {}", appPathIdentifier, httpResponse.getStatusCode()); if (httpResponse.getStatusCode() == Status.NOT_FOUND.getStatusCode()) { REREGISTER_COUNTER.increment(); logger.info(PREFIX + "{} - Re-registering apps/{}", appPathIdentifier, instanceInfo.getAppName()); long timestamp = instanceInfo.setIsDirtyWithTime(); boolean success = register(); if (success) { instanceInfo.unsetIsDirty(timestamp); } return success; } return httpResponse.getStatusCode() == Status.OK.getStatusCode(); } catch (Throwable e) { logger.error(PREFIX + "{} - was unable to send heartbeat!", appPathIdentifier, e); return false; } }
这里也就是维持心跳的核心逻辑，通过HttpClient访问心跳接口。
(4) com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient#sendHeartBeat 如下：
public EurekaHttpResponse<InstanceInfo> sendHeartBeat(String appName, String id, InstanceInfo info, InstanceStatus overriddenStatus) { String urlPath = "apps/" + appName + '/' + id; ClientResponse response = null; try { WebResource webResource = jerseyClient.resource(serviceUrl) .path(urlPath) .queryParam("status", info.getStatus().toString()) .queryParam("lastDirtyTimestamp", info.getLastDirtyTimestamp().toString()); if (overriddenStatus != null) { webResource = webResource.queryParam("overriddenstatus", overriddenStatus.name()); } Builder requestBuilder = webResource.getRequestBuilder(); addExtraHeaders(requestBuilder); response = requestBuilder.put(ClientResponse.class); EurekaHttpResponseBuilder<InstanceInfo> eurekaResponseBuilder = anEurekaHttpResponse(response.getStatus(), InstanceInfo.class).headers(headersOf(response)); if (response.hasEntity()) { eurekaResponseBuilder.entity(response.getEntity(InstanceInfo.class)); } return eurekaResponseBuilder.build(); } finally { if (logger.isDebugEnabled()) { logger.debug("Jersey HTTP PUT {}/{}; statusCode={}", serviceUrl, urlPath, response == null ? "N/A" : response.getStatus()); } if (response != null) { response.close(); } } }
其生成的url如下:
requestBuilder如下：
接下来调用requestBuilder.put(ClientResponse.class);发送心跳， 也就是通过Put方法发送心跳请求。(发送的信息包括自己的状态一个时间参数)
如果返回的结果是404(Status.NOT_FOUND)，就是说不存在，从来没有注册过，那么重新走注册流程。会进行下面一系列操作：
1》修改时间参数
com.netflix.discovery.DiscoveryClient#renew代码中instanceInfo.setIsDirtyWithTime()
com.netflix.appinfo.InstanceInfo#setIsDirtyWithTime
public synchronized long setIsDirtyWithTime() { setIsDirty(); return lastDirtyTimestamp; }
2》 重新注册服务
com.netflix.discovery.DiscoveryClient#register
/** * Register with the eureka service by making the appropriate REST call. */ boolean register() throws Throwable { logger.info(PREFIX + "{}: registering service...", appPathIdentifier); EurekaHttpResponse<Void> httpResponse; try { httpResponse = eurekaTransport.registrationClient.register(instanceInfo); } catch (Exception e) { logger.warn(PREFIX + "{} - registration failed {}", appPathIdentifier, e.getMessage(), e); throw e; } if (logger.isInfoEnabled()) { logger.info(PREFIX + "{} - registration status: {}", appPathIdentifier, httpResponse.getStatusCode()); } return httpResponse.getStatusCode() == Status.NO_CONTENT.getStatusCode(); }
最终调用到方法：com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient#register
@Override public EurekaHttpResponse<Void> register(InstanceInfo info) { String urlPath = "apps/" + info.getAppName(); ClientResponse response = null; try { Builder resourceBuilder = jerseyClient.resource(serviceUrl).path(urlPath).getRequestBuilder(); addExtraHeaders(resourceBuilder); response = resourceBuilder .header("Accept-Encoding", "gzip") .type(MediaType.APPLICATION_JSON_TYPE) .accept(MediaType.APPLICATION_JSON) .post(ClientResponse.class, info); return anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build(); } finally { if (logger.isDebugEnabled()) { logger.debug("Jersey HTTP POST {}/{} with instance {}; statusCode={}", serviceUrl, urlPath, info.getId(), response == null ? "N/A" : response.getStatus()); } if (response != null) { response.close(); } } }
3. com.netflix.discovery.DiscoveryClient#initScheduledTasks代码块中clientConfig.shouldRegisterWithEureka() 代码块走注册逻辑===下面主要是注册逻辑
(1) 创建com.netflix.discovery.InstanceInfoReplicator对象：
// InstanceInfo replicator instanceInfoReplicator = new InstanceInfoReplicator( this, instanceInfo, clientConfig.getInstanceInfoReplicationIntervalSeconds(), 2); // burstSize
构造如下：(创建一个scheduler 定时线程池)
InstanceInfoReplicator(DiscoveryClient discoveryClient, InstanceInfo instanceInfo, int replicationIntervalSeconds, int burstSize) { this.discoveryClient = discoveryClient; this.instanceInfo = instanceInfo; this.scheduler = Executors.newScheduledThreadPool(1, new ThreadFactoryBuilder() .setNameFormat("DiscoveryClient-InstanceInfoReplicator-%d") .setDaemon(true) .build()); this.scheduledPeriodicRef = new AtomicReference<Future>(); this.started = new AtomicBoolean(false); this.rateLimiter = new RateLimiter(TimeUnit.MINUTES); this.replicationIntervalSeconds = replicationIntervalSeconds; this.burstSize = burstSize; this.allowedRatePerMinute = 60 * this.burstSize / this.replicationIntervalSeconds; logger.info("InstanceInfoReplicator onDemand update allowed rate per min is {}", allowedRatePerMinute); }
最后一行代码如下：
instanceInfoReplicator.start(clientConfig.getInitialInstanceInfoReplicationIntervalSeconds())
clientConfig.getInitialInstanceInfoReplicationIntervalSeconds()返回的是：(默认40s向eureka更新实例信息)
/** * Indicates how long initially (in seconds) to replicate instance info to the eureka * server. */ private int initialInstanceInfoReplicationIntervalSeconds = 40;
com.netflix.discovery.InstanceInfoReplicator#start：(start方法里面开始注册==这里的start不是线程的启动方法，是一个同步方法)
public void start(int initialDelayMs) { if (started.compareAndSet(false, true)) { instanceInfo.setIsDirty(); // for initial register Future next = scheduler.schedule(this, initialDelayMs, TimeUnit.SECONDS); scheduledPeriodicRef.set(next); } }
scheduler.schedule(this, initialDelayMs, TimeUnit.SECONDS); 开始进行线程的启动执行：(线程启动调run方法)
public void run() { try { discoveryClient.refreshInstanceInfo(); Long dirtyTimestamp = instanceInfo.isDirtyWithTime(); if (dirtyTimestamp != null) { discoveryClient.register(); instanceInfo.unsetIsDirty(dirtyTimestamp); } } catch (Throwable t) { logger.warn("There was a problem with the instance info replicator", t); } finally { Future next = scheduler.schedule(this, replicationIntervalSeconds, TimeUnit.SECONDS); scheduledPeriodicRef.set(next); } }
run逻辑解释：
1》 discoveryClient.refreshInstanceInfo(); 方法更新实例信息
void refreshInstanceInfo() { applicationInfoManager.refreshDataCenterInfoIfRequired(); applicationInfoManager.refreshLeaseInfoIfRequired(); InstanceStatus status; try { status = getHealthCheckHandler().getStatus(instanceInfo.getStatus()); } catch (Exception e) { logger.warn("Exception from healthcheckHandler.getStatus, setting status to DOWN", e); status = InstanceStatus.DOWN; } if (null != status) { applicationInfoManager.setInstanceStatus(status); } }
(2) discoveryClient.register(); 方法进行注册
com.netflix.discovery.DiscoveryClient#register
boolean register() throws Throwable { logger.info(PREFIX + "{}: registering service...", appPathIdentifier); EurekaHttpResponse<Void> httpResponse; try { httpResponse = eurekaTransport.registrationClient.register(instanceInfo); } catch (Exception e) { logger.warn(PREFIX + "{} - registration failed {}", appPathIdentifier, e.getMessage(), e); throw e; } if (logger.isInfoEnabled()) { logger.info(PREFIX + "{} - registration status: {}", appPathIdentifier, httpResponse.getStatusCode()); } return httpResponse.getStatusCode() == Status.NO_CONTENT.getStatusCode(); }
最终调到com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient#register
public EurekaHttpResponse<Void> register(InstanceInfo info) { String urlPath = "apps/" + info.getAppName(); ClientResponse response = null; EurekaHttpResponse var5; try { Builder resourceBuilder = this.jerseyClient.resource(this.serviceUrl).path(urlPath).getRequestBuilder(); this.addExtraHeaders(resourceBuilder); response = (ClientResponse)((Builder)((Builder)((Builder)resourceBuilder.header("Accept-Encoding", "gzip")).type(MediaType.APPLICATION_JSON_TYPE)).accept(new String[]{"application/json"})).post(ClientResponse.class, info); var5 = EurekaHttpResponse.anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build(); } finally { if (logger.isDebugEnabled()) { logger.debug("Jersey HTTP POST {}/{} with instance {}; statusCode={}", new Object[]{this.serviceUrl, urlPath, info.getId(), response == null ? "N/A" : response.getStatus()}); } if (response != null) { response.close(); } } return var5; }
resourceBuilder如下：
发送的bean信息如下：
最终生成的requestImpl如下：
2. 服务获取
com.netflix.discovery.DiscoveryClient#initScheduledTasks 代码块中this.clientConfig.shouldFetchRegistry() 是获取服务的配置：
if (this.clientConfig.shouldFetchRegistry()) { renewalIntervalInSecs = this.clientConfig.getRegistryFetchIntervalSeconds(); expBackOffBound = this.clientConfig.getCacheRefreshExecutorExponentialBackOffBound(); this.scheduler.schedule(new TimedSupervisorTask("cacheRefresh", this.scheduler, this.cacheRefreshExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.CacheRefreshThread()), (long)renewalIntervalInSecs, TimeUnit.SECONDS); }
1. 拿到默认的时间：(30s)
private int registryFetchIntervalSeconds = 30;
2. 然后开启定时线程池，以30s为周期执行的线程任务如下：
new TimedSupervisorTask("cacheRefresh", this.scheduler, this.cacheRefreshExecutor, renewalIntervalInSecs, TimeUnit.SECONDS, expBackOffBound, new DiscoveryClient.CacheRefreshThread())
构造如下：
public TimedSupervisorTask(String name, ScheduledExecutorService scheduler, ThreadPoolExecutor executor, int timeout, TimeUnit timeUnit, int expBackOffBound, Runnable task) { this.scheduler = scheduler; this.executor = executor; this.timeoutMillis = timeUnit.toMillis((long)timeout); this.task = task; this.delay = new AtomicLong(this.timeoutMillis); this.maxDelay = this.timeoutMillis * (long)expBackOffBound; this.successCounter = Monitors.newCounter("success"); this.timeoutCounter = Monitors.newCounter("timeouts"); this.rejectedCounter = Monitors.newCounter("rejectedExecutions"); this.throwableCounter = Monitors.newCounter("throwables"); this.threadPoolLevelGauge = new LongGauge(MonitorConfig.builder("threadPoolUsed").build()); Monitors.registerObject(name, this); }
3. 然后会调用TimedSupervisorTask的run方法：
public void run() { Future future = null; try { future = this.executor.submit(this.task); this.threadPoolLevelGauge.set((long)this.executor.getActiveCount()); future.get(this.timeoutMillis, TimeUnit.MILLISECONDS); this.delay.set(this.timeoutMillis); this.threadPoolLevelGauge.set((long)this.executor.getActiveCount()); this.successCounter.increment(); } catch (TimeoutException var12) { logger.warn("task supervisor timed out", var12); this.timeoutCounter.increment(); long currentDelay = this.delay.get(); long newDelay = Math.min(this.maxDelay, currentDelay * 2L); this.delay.compareAndSet(currentDelay, newDelay); } catch (RejectedExecutionException var13) { if (!this.executor.isShutdown() && !this.scheduler.isShutdown()) { logger.warn("task supervisor rejected the task", var13); } else { logger.warn("task supervisor shutting down, reject the task", var13); } this.rejectedCounter.increment(); } catch (Throwable var14) { if (!this.executor.isShutdown() && !this.scheduler.isShutdown()) { logger.warn("task supervisor threw an exception", var14); } else { logger.warn("task supervisor shutting down, can't accept the task"); } this.throwableCounter.increment(); } finally { if (future != null) { future.cancel(true); } if (!this.scheduler.isShutdown()) { this.scheduler.schedule(this, this.delay.get(), TimeUnit.MILLISECONDS); } } }
里面又用一个线程池提交task任务，task任务是 构造方法传递的com.netflix.discovery.DiscoveryClient.CacheRefreshThread
class CacheRefreshThread implements Runnable { CacheRefreshThread() { } public void run() { DiscoveryClient.this.refreshRegistry(); } }
4. 最终调到：com.netflix.discovery.DiscoveryClient#refreshRegistry
void refreshRegistry() { try { boolean isFetchingRemoteRegionRegistries = this.isFetchingRemoteRegionRegistries(); boolean remoteRegionsModified = false; String latestRemoteRegions = this.clientConfig.fetchRegistryForRemoteRegions(); if (null != latestRemoteRegions) { String currentRemoteRegions = (String)this.remoteRegionsToFetch.get(); if (!latestRemoteRegions.equals(currentRemoteRegions)) { synchronized(this.instanceRegionChecker.getAzToRegionMapper()) { if (this.remoteRegionsToFetch.compareAndSet(currentRemoteRegions, latestRemoteRegions)) { String[] remoteRegions = latestRemoteRegions.split(","); this.remoteRegionsRef.set(remoteRegions); this.instanceRegionChecker.getAzToRegionMapper().setRegionsToFetch(remoteRegions); remoteRegionsModified = true; } else { logger.info("Remote regions to fetch modified concurrently, ignoring change from {} to {}", currentRemoteRegions, latestRemoteRegions); } } } else { this.instanceRegionChecker.getAzToRegionMapper().refreshMapping(); } } boolean success = this.fetchRegistry(remoteRegionsModified); if (success) { this.registrySize = ((Applications)this.localRegionApps.get()).size(); this.lastSuccessfulRegistryFetchTimestamp = System.currentTimeMillis(); } if (logger.isDebugEnabled()) { StringBuilder allAppsHashCodes = new StringBuilder(); allAppsHashCodes.append("Local region apps hashcode: "); allAppsHashCodes.append(((Applications)this.localRegionApps.get()).getAppsHashCode()); allAppsHashCodes.append(", is fetching remote regions? "); allAppsHashCodes.append(isFetchingRemoteRegionRegistries); Iterator var11 = this.remoteRegionVsApps.entrySet().iterator(); while(var11.hasNext()) { Entry<String, Applications> entry = (Entry)var11.next(); allAppsHashCodes.append(", Remote region: "); allAppsHashCodes.append((String)entry.getKey()); allAppsHashCodes.append(" , apps hashcode: "); allAppsHashCodes.append(((Applications)entry.getValue()).getAppsHashCode()); } logger.debug("Completed cache refresh task for discovery. All Apps hash code is {} ", allAppsHashCodes); } } catch (Throwable var9) { logger.error("Cannot fetch registry from server", var9); } }
this.fetchRegistry(remoteRegionsModified); 如下：
private boolean fetchRegistry(boolean forceFullRegistryFetch) { Stopwatch tracer = this.FETCH_REGISTRY_TIMER.start(); label122: { boolean var4; try { Applications applications = this.getApplications(); if (!this.clientConfig.shouldDisableDelta() && Strings.isNullOrEmpty(this.clientConfig.getRegistryRefreshSingleVipAddress()) && !forceFullRegistryFetch && applications != null && applications.getRegisteredApplications().size() != 0 && applications.getVersion().longValue() != -1L) { this.getAndUpdateDelta(applications); } else { logger.info("Disable delta property : {}", this.clientConfig.shouldDisableDelta()); logger.info("Single vip registry refresh property : {}", this.clientConfig.getRegistryRefreshSingleVipAddress()); logger.info("Force full registry fetch : {}", forceFullRegistryFetch); logger.info("Application is null : {}", applications == null); logger.info("Registered Applications size is zero : {}", applications.getRegisteredApplications().size() == 0); logger.info("Application version is -1: {}", applications.getVersion().longValue() == -1L); this.getAndStoreFullRegistry(); } applications.setAppsHashCode(applications.getReconcileHashCode()); this.logTotalInstances(); break label122; } catch (Throwable var8) { logger.error("DiscoveryClient_{} - was unable to refresh its cache! status = {}", new Object[]{this.appPathIdentifier, var8.getMessage(), var8}); var4 = false; } finally { if (tracer != null) { tracer.stop(); } } return var4; } this.onCacheRefreshed(); this.updateInstanceRemoteStatus(); return true; }
最后会走 com.netflix.discovery.DiscoveryClient#getAndUpdateDelta
private void getAndUpdateDelta(Applications applications) throws Throwable { long currentUpdateGeneration = this.fetchRegistryGeneration.get(); Applications delta = null; EurekaHttpResponse<Applications> httpResponse = this.eurekaTransport.queryClient.getDelta((String[])this.remoteRegionsRef.get()); if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) { delta = (Applications)httpResponse.getEntity(); } if (delta == null) { logger.warn("The server does not allow the delta revision to be applied because it is not safe. Hence got the full registry."); this.getAndStoreFullRegistry(); } else if (this.fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1L)) { logger.debug("Got delta update with apps hashcode {}", delta.getAppsHashCode()); String reconcileHashCode = ""; if (this.fetchRegistryUpdateLock.tryLock()) { try { this.updateDelta(delta); reconcileHashCode = this.getReconcileHashCode(applications); } finally { this.fetchRegistryUpdateLock.unlock(); } } else { logger.warn("Cannot acquire update lock, aborting getAndUpdateDelta"); } if (!reconcileHashCode.equals(delta.getAppsHashCode()) || this.clientConfig.shouldLogDeltaDiff()) { this.reconcileAndLogDifference(delta, reconcileHashCode); } } else { logger.warn("Not updating application delta as another thread is updating it already"); logger.debug("Ignoring delta update with apps hashcode {}, as another thread is updating it already", delta.getAppsHashCode()); } }
最后调到方法：com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient#getDelta
public EurekaHttpResponse<Applications> getDelta(String... regions) { return this.getApplicationsInternal("apps/delta", regions); } private EurekaHttpResponse<Applications> getApplicationsInternal(String urlPath, String[] regions) { ClientResponse response = null; String regionsParamValue = null; EurekaHttpResponse var8; try { WebResource webResource = this.jerseyClient.resource(this.serviceUrl).path(urlPath); if (regions != null && regions.length > 0) { regionsParamValue = StringUtil.join(regions); webResource = webResource.queryParam("regions", regionsParamValue); } Builder requestBuilder = webResource.getRequestBuilder(); this.addExtraHeaders(requestBuilder); response = (ClientResponse)((Builder)requestBuilder.accept(new MediaType[]{MediaType.APPLICATION_JSON_TYPE})).get(ClientResponse.class); Applications applications = null; if (response.getStatus() == Status.OK.getStatusCode() && response.hasEntity()) { applications = (Applications)response.getEntity(Applications.class); } var8 = EurekaHttpResponse.anEurekaHttpResponse(response.getStatus(), Applications.class).headers(headersOf(response)).entity(applications).build(); } finally { if (logger.isDebugEnabled()) { logger.debug("Jersey HTTP GET {}/{}?{}; statusCode={}", new Object[]{this.serviceUrl, urlPath, regionsParamValue == null ? "" : "regions=" + regionsParamValue, response == null ? "N/A" : response.getStatus()}); } if (response != null) { response.close(); } } return var8; }
生成的requestBuilder如下：
最后调用返回的response信息如下：
拿到应用信息之后返回比较之后进行更新。
也就是说服务获取时候是scheduler里面又用一个ThreadPoolExecutor 线程池进行服务获取。这里的任务调度线程scheduler和上面心跳是同一个scheduler。
3. 服务注销
服务注销需要追溯到服务销毁时候的 shutdown 方法，com.netflix.discovery.DiscoveryClient#shutdown
@PreDestroy public synchronized void shutdown() { if (this.isShutdown.compareAndSet(false, true)) { logger.info("Shutting down DiscoveryClient ..."); if (this.statusChangeListener != null && this.applicationInfoManager != null) { this.applicationInfoManager.unregisterStatusChangeListener(this.statusChangeListener.getId()); } this.cancelScheduledTasks(); if (this.applicationInfoManager != null && this.clientConfig.shouldRegisterWithEureka() && this.clientConfig.shouldUnregisterOnShutdown()) { this.applicationInfoManager.setInstanceStatus(InstanceStatus.DOWN); this.unregister(); } if (this.eurekaTransport != null) { this.eurekaTransport.shutdown(); } this.heartbeatStalenessMonitor.shutdown(); this.registryStalenessMonitor.shutdown(); logger.info("Completed shut down of DiscoveryClient"); } }
可以看到代码取消了定时任务，然后调用unregister() 方法。com.netflix.discovery.DiscoveryClient#unregister：
void unregister() { if (this.eurekaTransport != null && this.eurekaTransport.registrationClient != null) { try { logger.info("Unregistering ..."); EurekaHttpResponse<Void> httpResponse = this.eurekaTransport.registrationClient.cancel(this.instanceInfo.getAppName(), this.instanceInfo.getId()); logger.info("DiscoveryClient_{} - deregister status: {}", this.appPathIdentifier, httpResponse.getStatusCode()); } catch (Exception var2) { logger.error("DiscoveryClient_{} - de-registration failed{}", new Object[]{this.appPathIdentifier, var2.getMessage(), var2}); } } }
最终调到com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient#cancel：
public EurekaHttpResponse<Void> cancel(String appName, String id) { String urlPath = "apps/" + appName + '/' + id; ClientResponse response = null; EurekaHttpResponse var6; try { Builder resourceBuilder = this.jerseyClient.resource(this.serviceUrl).path(urlPath).getRequestBuilder(); this.addExtraHeaders(resourceBuilder); response = (ClientResponse)resourceBuilder.delete(ClientResponse.class); var6 = EurekaHttpResponse.anEurekaHttpResponse(response.getStatus()).headers(headersOf(response)).build(); } finally { if (logger.isDebugEnabled()) { logger.debug("Jersey HTTP DELETE {}/{}; statusCode={}", new Object[]{this.serviceUrl, urlPath, response == null ? "N/A" : response.getStatus()}); } if (response != null) { response.close(); } } return var6; }
可以看出来是通过delete方法调用接口： http://localhost:7001/eureka/apps/ + appName + '/' + instanceId 删除服务
总结：
其实Client端核心的入口就是如下构造方法：
com.netflix.discovery.DiscoveryClient#DiscoveryClient(com.netflix.appinfo.ApplicationInfoManager, com.netflix.discovery.EurekaClientConfig, com.netflix.discovery.AbstractDiscoveryClientOptionalArgs, javax.inject.Provider<com.netflix.discovery.BackupRegistry>, com.netflix.discovery.shared.resolver.EndpointRandomizer)
构造方法创建了scheduler任务调度器，线程池大小为2；分别跑心跳任务heartbeat和获取服务的cacheRefresh 任务。需要注意调度器中的任务又是在线程池中跑的，分别对应heartbeatExecutor和cacheRefreshExecutor。异步任务执行完会再次开启scheduler任务调度，造成一个周期性任务调度的效果。renewalIntervalInSecs 心跳周期默认30s；registryFetchIntervalSeconds 服务获取周期默认是30 s。
com.netflix.discovery.DiscoveryClient#initScheduledTasks方法中创建了一个instanceInfoReplicator，instanceInfoReplicator 构造中创建了一个线程池大小为1 的scheduler，用于跑注册服务(更新服务信息)的任务。 这个任务调度器跑的任务就是直接是InstanceInfoReplicator 自身，也就是跑其run方法，run方法结束继续任务调度。 也就是服务注册是scheduler 直接调度任务，没有再用线程池。initialInstanceInfoReplicationIntervalSeconds 更新服务信息周期 默认40s；
补充：Eureka客户端请求地址，可以通过自己curl进行调用
1. 维持心跳
http://localhost:7001/eureka/apps/appName/instanceId?status=UP&lastDirtyTimestamp=1615368528026
例如：
http://localhost:7001/eureka/apps/CLOUD-PROVIDER-HYSTRIX-PAYMENT/QLQ-T460:cloud-provider-hystrix-payment:0?status=UP&lastDirtyTimestamp=1615368528026
补充：应用名称(服务名)变为大写
1. 如下方法： org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration.RefreshableEurekaClientConfiguration#eurekaApplicationInfoManager
@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); }
2. 调用对象工厂使用建造者模式创建对象org.springframework.cloud.netflix.eureka.InstanceInfoFactory#create
public InstanceInfo create(EurekaInstanceConfig config) { LeaseInfo.Builder leaseInfoBuilder = LeaseInfo.Builder.newBuilder() .setRenewalIntervalInSecs(config.getLeaseRenewalIntervalInSeconds()) .setDurationInSecs(config.getLeaseExpirationDurationInSeconds()); // Builder the instance information to be registered with eureka // server InstanceInfo.Builder builder = InstanceInfo.Builder.newBuilder(); String namespace = config.getNamespace(); if (!namespace.endsWith(".")) { namespace = namespace + "."; } builder.setNamespace(namespace).setAppName(config.getAppname()) .setInstanceId(config.getInstanceId()) .setAppGroupName(config.getAppGroupName()) .setDataCenterInfo(config.getDataCenterInfo()) .setIPAddr(config.getIpAddress()).setHostName(config.getHostName(false)) .setPort(config.getNonSecurePort()) .enablePort(InstanceInfo.PortType.UNSECURE, config.isNonSecurePortEnabled()) .setSecurePort(config.getSecurePort()) .enablePort(InstanceInfo.PortType.SECURE, config.getSecurePortEnabled()) .setVIPAddress(config.getVirtualHostName()) .setSecureVIPAddress(config.getSecureVirtualHostName()) .setHomePageUrl(config.getHomePageUrlPath(), config.getHomePageUrl()) .setStatusPageUrl(config.getStatusPageUrlPath(), config.getStatusPageUrl()) .setHealthCheckUrls(config.getHealthCheckUrlPath(), config.getHealthCheckUrl(), config.getSecureHealthCheckUrl()) .setASGName(config.getASGName()); // Start off with the STARTING state to avoid traffic if (!config.isInstanceEnabledOnit()) { InstanceInfo.InstanceStatus initialStatus = InstanceInfo.InstanceStatus.STARTING; if (log.isInfoEnabled()) { log.info("Setting initial instance status as: " + initialStatus); } builder.setStatus(initialStatus); } else { if (log.isInfoEnabled()) { log.info("Setting initial instance status as: " + InstanceInfo.InstanceStatus.UP + ". This may be too early for the instance to advertise itself as available. " + "You would instead want to control this via a healthcheck handler."); } } // Add any user-specific metadata information for (Map.Entry<String, String> mapEntry : config.getMetadataMap().entrySet()) { String key = mapEntry.getKey(); String value = mapEntry.getValue(); // only add the metadata if the value is present if (value != null && !value.isEmpty()) { builder.add(key, value); } } InstanceInfo instanceInfo = builder.build(); instanceInfo.setLeaseInfo(leaseInfoBuilder.build()); return instanceInfo; }
3. 建造者的setAppnName方法com.netflix.appinfo.InstanceInfo.Builder#setAppName
public Builder setAppName(String appName) { result.appName = intern.apply(appName.toUpperCase(Locale.ROOT)); return this; }
补充：Scheuler 任务调度器调度多个周期任务的写法
package test; import lombok.extern.slf4j.Slf4j; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; @Slf4j public class PlainTest { public static void main(String[] args) { ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1); scheduledExecutorService.schedule(new Runnable() { @Override public void run() { log.error("5s" + Thread.currentThread().getName()); // 再次任务调度 scheduledExecutorService.schedule(this, 5, TimeUnit.SECONDS); } }, 5, TimeUnit.SECONDS); scheduledExecutorService.schedule(new Runnable() { @Override public void run() { log.error("10s" + Thread.currentThread().getName()); scheduledExecutorService.schedule(this, 10, TimeUnit.SECONDS); } }, 10, TimeUnit.SECONDS); } }
补充：集群模式下Client 发送请求的规则
其实Eureka集群是没有主从节点之后，都是平等节点。EurekaServer 收到客户端请求的操作是： 如果正常操作完成，会通知兄弟姐妹节点做同等的操作。
EurekaClient 的操作是，从配置的集群节点默认选择最后一个为发送的节点；如果当前节点不可用则重试前面的节点。
1. 集群模式客户端的配置
eureka: client: register-with-eureka: true fetch-registry: true service-url: defaultZone: http://localhost:7001/eureka,http://localhost:7002/eureka
2. 以注册为入口研究：
(1) com.netflix.discovery.DiscoveryClient#register 方法为入口：
(2) 方法调用到 com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator#register
public EurekaHttpResponse<Void> register(final InstanceInfo info) { return execute(new RequestExecutor<Void>() { @Override public EurekaHttpResponse<Void> execute(EurekaHttpClient delegate) { return delegate.register(info); } @Override public RequestType getRequestType() { return RequestType.Register; } }); }
(3) 接下来调用com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient#execute
(4) 接下来调用到com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient#execute
protected <R> EurekaHttpResponse<R> execute(RequestExecutor<R> requestExecutor) { List<EurekaEndpoint> candidateHosts = null; int endpointIdx = 0; for (int retry = 0; retry < numberOfRetries; retry++) { EurekaHttpClient currentHttpClient = delegate.get(); EurekaEndpoint currentEndpoint = null; if (currentHttpClient == null) { if (candidateHosts == null) { candidateHosts = getHostCandidates(); if (candidateHosts.isEmpty()) { throw new TransportException("There is no known eureka server; cluster server list is empty"); } } if (endpointIdx >= candidateHosts.size()) { throw new TransportException("Cannot execute request on any known server"); } currentEndpoint = candidateHosts.get(endpointIdx++); currentHttpClient = clientFactory.newClient(currentEndpoint); } try { EurekaHttpResponse<R> response = requestExecutor.execute(currentHttpClient); if (serverStatusEvaluator.accept(response.getStatusCode(), requestExecutor.getRequestType())) { delegate.set(currentHttpClient); if (retry > 0) { logger.info("Request execution succeeded on retry #{}", retry); } return response; } logger.warn("Request execution failure with status code {}; retrying on another server if available", response.getStatusCode()); } catch (Exception e) { logger.warn("Request execution failed with message: {}", e.getMessage()); // just log message as the underlying client should log the stacktrace } // Connection error or 5xx from the server that must be retried on another server delegate.compareAndSet(currentHttpClient, null); if (currentEndpoint != null) { quarantineSet.add(currentEndpoint); } } throw new TransportException("Retry limit reached; giving up on completing the request"); }
方法内部第一次进来currentHttpClient 为空，然后创建currentHttpClient 对象
获取到的List<EurekaEndpoint> 备用端点如下：
然后以第一个的地址创建EurekaHttpClient 之后存入delegate。创建的对象如下：
(5) 假设我们的7002端口服务断掉： 则不会走try代码块的return 语句。 打印日志之后走最后的清除currentHttpClient 代码。然后retry++进行下一次尝试，打印的日志如下：
2021-03-16 20:24:42.632 ERROR 33480 --- [ main] c.n.d.s.t.d.RedirectingEurekaHttpClient : Request execution error. endpoint=DefaultEndpoint{ serviceUrl='http://localhost:7002/eureka/}
com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused: connect
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar:1.19.1]
at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.9.13.jar:1.9.13]
at com.sun.jersey.api.client.Client.handle(Client.java:652) ~[jersey-client-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682) ~[jersey-client-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) ~[jersey-client-1.19.1.jar:1.19.1]
at com.sun.jersey.api.client.WebResource$Builder.get(WebResource.java:509) ~[jersey-client-1.19.1.jar:1.19.1]
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getApplicationsInternal(AbstractJerseyEurekaHttpClient.java:194) ~[eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.getApplications(AbstractJerseyEurekaHttpClient.java:165) ~[eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73) ~[eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:118) ~[eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:79) ~[eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:120) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$6.execute(EurekaHttpClientDecorator.java:137) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.getApplications(EurekaHttpClientDecorator.java:134) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.DiscoveryClient.getAndStoreFullRegistry(DiscoveryClient.java:1069) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.DiscoveryClient.fetchRegistry(DiscoveryClient.java:983) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:430) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:276) [eureka-client-1.9.13.jar:1.9.13]
at com.netflix.discovery.DiscoveryClient.<init>(DiscoveryClient.java:272) [eureka-client-1.9.13.jar:1.9.13]
at org.springframework.cloud.netflix.eureka.CloudEurekaClient.<init>(CloudEurekaClient.java:67) [spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration$RefreshableEurekaClientConfiguration.eurekaClient(EurekaClientAutoConfiguration.java:324) [spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_171]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:154) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:651) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:636) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$1(AbstractBeanFactory.java:359) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.cloud.context.scope.GenericScope$BeanLifecycleWrapper.getBean(GenericScope.java:389) ~[spring-cloud-context-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.cloud.context.scope.GenericScope.get(GenericScope.java:186) ~[spring-cloud-context-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:356) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) [spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.aop.target.SimpleBeanTargetSource.getTarget(SimpleBeanTargetSource.java:35) ~[spring-aop-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaRegistration.getTargetObject(EurekaRegistration.java:129) ~[spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaRegistration.getEurekaClient(EurekaRegistration.java:117) ~[spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_171]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_171]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_171]
at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_171]
at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:282) ~[spring-core-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.cloud.context.scope.GenericScope$LockedScopedProxyFactoryBean.invoke(GenericScope.java:499) ~[spring-cloud-context-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) ~[spring-aop-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:747) ~[spring-aop-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:689) ~[spring-aop-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaRegistration$$EnhancerBySpringCGLIB$$cfe6ed5b.getEurekaClient(<generated>) ~[spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaServiceRegistry.maybeInitializeClient(EurekaServiceRegistry.java:57) ~[spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaServiceRegistry.register(EurekaServiceRegistry.java:38) ~[spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaAutoServiceRegistration.start(EurekaAutoServiceRegistration.java:83) ~[spring-cloud-netflix-eureka-client-2.2.1.RELEASE.jar:2.2.1.RELEASE]
at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:182) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:53) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:360) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:158) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:122) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:894) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.finishRefresh(ServletWebServerApplicationContext.java:162) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:553) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
at cn.qz.cloud.PaymentHystrixMain8081.main(PaymentHystrixMain8081.java:32) ~[classes/:na]
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method) ~[na:1.8.0_171]
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85) ~[na:1.8.0_171]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_171]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_171]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_171]
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172) ~[na:1.8.0_171]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_171]
at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_171]
at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:605) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:440) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.10.jar:4.5.10]
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.10.jar:4.5.10]
at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
... 75 common frames omitted
2021-03-16 20:24:48.653 WARN 33480 --- [ main] c.n.d.s.t.d.RetryableEurekaHttpClient : Request execution failed with message: java.net.ConnectException: Connection refused: connect
2021-03-16 20:25:38.674 INFO 33480 --- [ main] c.n.d.s.t.d.RetryableEurekaHttpClient : Request execution succeeded on retry #1
(6) 如果EurekaServer 下次上线又可以作为备用服务节点进行选择， 因为每次请求进来都是for循环开始。 如果这时候7001 也下线，则两个节点都下线，进来转一圈后报错。 如果有7001或者7002上线，在下次请求进来时会选择节点进行尝试。
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