一： 服务的注册
客户端通过执行InstanceInfoReplicator#run()调用DiscoveryClient#register()发送http请求进行注册
InstanceInfoReplicator是同于更新同步当前服务到服务端的任务实现
//A task for updating and replicating the local instanceinfo to the remote server.
//服务注册
boolean register() throws Throwable {logger.info("DiscoveryClient_{}: registering service...", this.appPathIdentifier);EurekaHttpResponse httpResponse;try {httpResponse = this.eurekaTransport.registrationClient.register(this.instanceInfo);} catch (Exception var3) {Exception e = var3;logger.warn("DiscoveryClient_{} - registration failed {}", new Object[]{this.appPathIdentifier, e.getMessage(), e});throw e;}if (logger.isInfoEnabled()) {logger.info("DiscoveryClient_{} - registration status: {}", this.appPathIdentifier, httpResponse.getStatusCode());}return httpResponse.getStatusCode() == Status.NO_CONTENT.getStatusCode();}
//服务续约
/**
eureka 初始化定时任务，依据设定的心跳时间触发 renew方法，检测服务是否宕机
*/boolean renew() {try {EurekaHttpResponse<InstanceInfo> httpResponse = this.eurekaTransport.registrationClient.sendHeartBeat(this.instanceInfo.getAppName(), this.instanceInfo.getId(), this.instanceInfo, (InstanceInfo.InstanceStatus)null);logger.debug("DiscoveryClient_{} - Heartbeat status: {}", this.appPathIdentifier, httpResponse.getStatusCode());if (httpResponse.getStatusCode() == Status.NOT_FOUND.getStatusCode()) {this.REREGISTER_COUNTER.increment();logger.info("DiscoveryClient_{} - Re-registering apps/{}", this.appPathIdentifier, this.instanceInfo.getAppName());long timestamp = this.instanceInfo.setIsDirtyWithTime();boolean success = this.register();if (success) {this.instanceInfo.unsetIsDirty(timestamp);}return success;} else {return httpResponse.getStatusCode() == Status.OK.getStatusCode();}} catch (Throwable var5) {Throwable e = var5;logger.error("DiscoveryClient_{} - was unable to send heartbeat!", this.appPathIdentifier, e);return false;}}
服务端服务注册接受和存储
//eureka 客户端会通过此方法注册保存到eureka server 的内存中
public void register(InstanceInfo registrant, int leaseDuration, boolean isReplication) {this.read.lock();try {Map<String, Lease<InstanceInfo>> gMap = (Map)this.registry.get(registrant.getAppName());EurekaMonitors.REGISTER.increment(isReplication);if (gMap == null) {ConcurrentHashMap<String, Lease<InstanceInfo>> gNewMap = new ConcurrentHashMap();gMap = (Map)this.registry.putIfAbsent(registrant.getAppName(), gNewMap);if (gMap == null) {gMap = gNewMap;}}Lease<InstanceInfo> existingLease = (Lease)((Map)gMap).get(registrant.getId());if (existingLease != null && existingLease.getHolder() != null) {Long existingLastDirtyTimestamp = ((InstanceInfo)existingLease.getHolder()).getLastDirtyTimestamp();Long registrationLastDirtyTimestamp = registrant.getLastDirtyTimestamp();logger.debug("Existing lease found (existing={}, provided={}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);if (existingLastDirtyTimestamp > registrationLastDirtyTimestamp) {logger.warn("There is an existing lease and the existing lease's dirty timestamp {} is greater than the one that is being registered {}", existingLastDirtyTimestamp, registrationLastDirtyTimestamp);logger.warn("Using the existing instanceInfo instead of the new instanceInfo as the registrant");registrant = (InstanceInfo)existingLease.getHolder();}} else {synchronized(this.lock) {if (this.expectedNumberOfClientsSendingRenews > 0) {++this.expectedNumberOfClientsSendingRenews;this.updateRenewsPerMinThreshold();}}logger.debug("No previous lease information found; it is new registration");}Lease<InstanceInfo> lease = new Lease(registrant, leaseDuration);if (existingLease != null) {lease.setServiceUpTimestamp(existingLease.getServiceUpTimestamp());}((Map)gMap).put(registrant.getId(), lease);this.recentRegisteredQueue.add(new Pair(System.currentTimeMillis(), registrant.getAppName() + "(" + registrant.getId() + ")"));if (!InstanceStatus.UNKNOWN.equals(registrant.getOverriddenStatus())) {logger.debug("Found overridden status {} for instance {}. Checking to see if needs to be add to the overrides", registrant.getOverriddenStatus(), registrant.getId());if (!this.overriddenInstanceStatusMap.containsKey(registrant.getId())) {logger.info("Not found overridden id {} and hence adding it", registrant.getId());this.overriddenInstanceStatusMap.put(registrant.getId(), registrant.getOverriddenStatus());}}InstanceInfo.InstanceStatus overriddenStatusFromMap = (InstanceInfo.InstanceStatus)this.overriddenInstanceStatusMap.get(registrant.getId());if (overriddenStatusFromMap != null) {logger.info("Storing overridden status {} from map", overriddenStatusFromMap);registrant.setOverriddenStatus(overriddenStatusFromMap);}InstanceInfo.InstanceStatus overriddenInstanceStatus = this.getOverriddenInstanceStatus(registrant, existingLease, isReplication);registrant.setStatusWithoutDirty(overriddenInstanceStatus);if (InstanceStatus.UP.equals(registrant.getStatus())) {lease.serviceUp();}registrant.setActionType(ActionType.ADDED);this.recentlyChangedQueue.add(new RecentlyChangedItem(lease));registrant.setLastUpdatedTimestamp();this.invalidateCache(registrant.getAppName(), registrant.getVIPAddress(), registrant.getSecureVipAddress());logger.info("Registered instance {}/{} with status {} (replication={})", new Object[]{registrant.getAppName(), registrant.getId(), registrant.getStatus(), isReplication});} finally {this.read.unlock();}}
如图，registry保存有将注册、已注册到server 的eureka客户端 instance信息；
将要注册到注册表registry中的instance，会创建一个map结构保存
二： 服务的发现
依据上图展示，服务注册采取的是客户端创立DiscoveryClient建立http请求，同理利用此DiscoveryClient实例通过请求完成服务的发现，不再赘述；
重点将放入服务发现的缓存和调用
1.
//其他发现实现 DiscoveryClient#getAndUpdateDelta 包括更新等具体操作不作继续深入讨论/*** Gets the full registry information from the eureka server and stores it locally.* When applying the full registry, the following flow is observed:** if (update generation have not advanced (due to another thread))* atomically set the registry to the new registry* fi** @return the full registry information.* @throws Throwable* on error.*/private void getAndStoreFullRegistry() throws Throwable {long currentUpdateGeneration = fetchRegistryGeneration.get();logger.info("Getting all instance registry info from the eureka server");Applications apps = null;EurekaHttpResponse<Applications> httpResponse = clientConfig.getRegistryRefreshSingleVipAddress() == null? eurekaTransport.queryClient.getApplications(remoteRegionsRef.get()): eurekaTransport.queryClient.getVip(clientConfig.getRegistryRefreshSingleVipAddress(), remoteRegionsRef.get());if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {apps = httpResponse.getEntity();}logger.info("The response status is {}", httpResponse.getStatusCode());if (apps == null) {logger.error("The application is null for some reason. Not storing this information");} else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {//存入本地服务缓存，即客户端将server端的服务注册信息缓存了一份，存在后续的缓存更新机制不做深入//this.filterAndShuffle(apps) 目的是处理 UP 状态的实例以及 打乱保证随机性 // Shuffling helps in randomizing the applications list there by avoiding the same instances receiving traffic during start ups.localRegionApps.set(this.filterAndShuffle(apps));logger.debug("Got full registry with apps hashcode {}", apps.getAppsHashCode());} else {logger.warn("Not updating applications as another thread is updating it already");}}
2. 调用
一： 利用DiscoveryClient获取实例的信息，再构建http请求
二： 使用组件fegin完成服务转发
@FeignClient(value = "eurekaclient")
public interface ApiService {@RequestMapping(value = "/index",method = RequestMethod.GET)String index();
}/**
等价于 new httpclient(eurekaClient) => 发送 /index 接口并接受到response
*/
