在Eureka - Client服务启动我们看到，注册表获取的地方有两个，一个是EurekaClient构造函数，一个是定时器每隔30秒去获取。我们先看看定时器TimedSupervisorTask的run方法
定时器
这个方法有三个比较重要的参数，timeoutMillis、delay、maxDelay。比如频率是30s，那这个maxDelay就是30*10=300s（这个10的来源参考上一篇），delay在这里是每次都翻倍，但是不能比maxDelay大。
整个设计思路是，如果调用30s超时，那就用60秒，如果再超时，就一直翻，但是不能超过300s。如果在后面的调用中正常了，那delay就恢复到30s，下次超时继续翻倍。
@Override
public void run() {
Future future = null;
try {
// 执行任务
future = executor.submit(task);
threadPoolLevelGauge.set((long) executor.getActiveCount());
// 指定超时时间
future.get(timeoutMillis, TimeUnit.MILLISECONDS); // block until done or timeout
//设置delay
delay.set(timeoutMillis);
threadPoolLevelGauge.set((long) executor.getActiveCount());
successCounter.increment();
} catch (TimeoutException e) {
logger.warn("task supervisor timed out", e);
timeoutCounter.increment();
// 获取delay
long currentDelay = delay.get();
// maxDelay和currentDelay的2倍中取最小值
long newDelay = Math.min(maxDelay, currentDelay * 2);
// 设置为上面最小值
delay.compareAndSet(currentDelay, newDelay);
} catch (RejectedExecutionException e) {
// 其他的略
rejectedCounter.increment();
} catch (Throwable e) {
// 其他的略
throwableCounter.increment();
} finally {
if (future != null) {
future.cancel(true);
}
// 把任务放入定时器，时间是delay
if (!scheduler.isShutdown()) {
scheduler.schedule(this, delay.get(), TimeUnit.MILLISECONDS);
}
}
}服务发现
判断增量获取还是全量获取
private boolean fetchRegistry(boolean forceFullRegistryFetch) {
Stopwatch tracer = FETCH_REGISTRY_TIMER.start();
try {
Applications applications = getApplications();
// 禁用增量、强制全量更新、没有注册信息的时候，进行全量更新
if (clientConfig.shouldDisableDelta()
|| (!Strings.isNullOrEmpty(clientConfig.getRegistryRefreshSingleVipAddress()))
|| forceFullRegistryFetch
|| (applications == null)
|| (applications.getRegisteredApplications().size() == 0)
|| (applications.getVersion() == -1)) //Client application does not have latest library supporting delta
{
// 其他日志打印略
getAndStoreFullRegistry();
} else {
//增量更新
getAndUpdateDelta(applications);
}
// 计算hash
applications.setAppsHashCode(applications.getReconcileHashCode());
logTotalInstances();
} catch (Throwable e) {
// 其他日志打印略
return false;
} finally {
if (tracer != null) {
tracer.stop();
}
}
// 其他略
return true;
}全量获取
全量获取，调用注册中心地址+apps/获取。
private void getAndStoreFullRegistry() throws Throwable {
// 其他略
Applications apps = null;
// 调用注册中心地址+apps/获取
EurekaHttpResponse 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();
}
// 其他略
} 增量获取
增量更新，获取后，通过hash要判断是否和服务器一致，不一致就全量
private void getAndUpdateDelta(Applications applications) throws Throwable {
long currentUpdateGeneration = fetchRegistryGeneration.get();
Applications delta = null;
// 调用注册中心地址+apps/delta获取
EurekaHttpResponse httpResponse = eurekaTransport.queryClient.getDelta(remoteRegionsRef.get());
if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {
delta = httpResponse.getEntity();
}
if (delta == null) {
//获取不到数据，全力更新
getAndStoreFullRegistry();
} else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {
logger.debug("Got delta update with apps hashcode {}", delta.getAppsHashCode());
String reconcileHashCode = "";
//加锁
if (fetchRegistryUpdateLock.tryLock()) {
try {
// 和本地的合并
updateDelta(delta);
// 计算hash
reconcileHashCode = getReconcileHashCode(applications);
} finally {
//解锁
fetchRegistryUpdateLock.unlock();
}
} else {
logger.warn("Cannot acquire update lock, aborting getAndUpdateDelta");
}
// There is a diff in number of instances for some reason
// 和服务器的hash对比
if (!reconcileHashCode.equals(delta.getAppsHashCode()) || clientConfig.shouldLogDeltaDiff()) {
// 不一致说明和服务器的不一致，直接全量
reconcileAndLogDifference(delta, reconcileHashCode); // this makes a remoteCall
}
} else {
// 其他略
}
} 和本地数据的合并，包括新增、修改、删除。
private void updateDelta(Applications delta) {
int deltaCount = 0;
// 遍历所有增量
for (Application app : delta.getRegisteredApplications()) {
// 遍历所有实例
for (InstanceInfo instance : app.getInstances()) {
// 本地缓存
Applications applications = getApplications();
String instanceRegion = instanceRegionChecker.getInstanceRegion(instance);
// 是否为同一个region，如果不是，则取同一个region的applications
if (!instanceRegionChecker.isLocalRegion(instanceRegion)) {
Applications remoteApps = remoteRegionVsApps.get(instanceRegion);
if (null == remoteApps) {
remoteApps = new Applications();
remoteRegionVsApps.put(instanceRegion, remoteApps);
}
applications = remoteApps;
}
++deltaCount;
if (ActionType.ADDED.equals(instance.getActionType())) {
// 新增处理
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Added instance {} to the existing apps in region {}", instance.getId(), instanceRegion);
applications.getRegisteredApplications(instance.getAppName()).addInstance(instance);
} else if (ActionType.MODIFIED.equals(instance.getActionType())) {
// 修改处理
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp == null) {
applications.addApplication(app);
}
logger.debug("Modified instance {} to the existing apps ", instance.getId());
// 和新增都是调用addInstance方法，因为Application#addInstance里是先移除再新增，所有修改也可以调用
applications.getRegisteredApplications(instance.getAppName()).addInstance(instance);
} else if (ActionType.DELETED.equals(instance.getActionType())) {
// 删除处理
Application existingApp = applications.getRegisteredApplications(instance.getAppName());
if (existingApp != null) {
logger.debug("Deleted instance {} to the existing apps ", instance.getId());
existingApp.removeInstance(instance);
if (existingApp.getInstancesAsIsFromEureka().isEmpty()) {
applications.removeApplication(existingApp);
}
}
}
}
}
logger.debug("The total number of instances fetched by the delta processor : {}", deltaCount);
getApplications().setVersion(delta.getVersion());
getApplications().shuffleInstances(clientConfig.shouldFilterOnlyUpInstances());
for (Applications applications : remoteRegionVsApps.values()) {
applications.setVersion(delta.getVersion());
applications.shuffleInstances(clientConfig.shouldFilterOnlyUpInstances());
}
}