Eureka服务注册发现源码流程简析
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
*/
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