// 获取所有注册表信息
private void getAndStoreFullRegistry() throws Throwable {
    long currentUpdateGeneration = fetchRegistryGeneration.get();

    Applications apps = null;
    // 交给网络传输组件，发起网络请求，获得响应
    EurekaHttpResponse httpResponse = clientConfig.getRegistryRefreshSingleVipAddress() == null
              // todo apps请求url
            ? eurekaTransport.queryClient.getApplications(remoteRegionsRef.get())
            : eurekaTransport.queryClient.getVip(clientConfig.getRegistryRefreshSingleVipAddress(), remoteRegionsRef.get());
    if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {
        apps = httpResponse.getEntity();
    }

    if (apps == null) {
        logger.error("The application is null for some reason. Not storing this information");
    } else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {
        //
        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");
    }
}

这里其实就是调用网络组件来发起请求，得到响应了，然后拿到所有得实例信息后，将实例信息设置到本地注册表中。 我们这里再深入一点，看看eurekaTransport.queryClient.getApplications(remoteRegionsRef.get()) 是请求得哪个url：hni拜客生活常识网

@Override
public EurekaHttpResponse getApplications(String... regions) {
    return getApplicationsInternal("apps/", regions);
}
private EurekaHttpResponse getApplicationsInternal(String urlPath, String[] regions) {
    ClientResponse response = null;
    String regionsParamValue = null;
    try {
        WebResource webResource = jerseyClient.resource(serviceUrl).path(urlPath);
        // 拼接region
        if (regions != null && regions.length > 0) {
            regionsParamValue = StringUtil.join(regions);
            webResource = webResource.queryParam("regions", regionsParamValue);
        }
        Builder requestBuilder = webResource.getRequestBuilder();
        addExtraHeaders(requestBuilder);
        // 提交get请求
        response = requestBuilder.accept(MediaType.APPLICATION_JSON_TYPE).get(ClientResponse.class);

        Applications applications = null;
        if (response.getStatus() == Status.OK.getStatusCode() && response.hasEntity()) {
            applications = response.getEntity(Applications.class);
        }
        return anEurekaHttpResponse(response.getStatus(), Applications.class)
                .headers(headersOf(response))
                .entity(applications)
                .build();
    } 
}

拉取全量注册表的请求为：GET请求，path为：apps/hni拜客生活常识网

4.1.2 增量拉取注册表信息

getAndUpdateDelta(applications);代码如下：hni拜客生活常识网

private void getAndUpdateDelta(Applications applications) throws Throwable {
    long currentUpdateGeneration = fetchRegistryGeneration.get();

    Applications delta = null;
    // 提交请求
    EurekaHttpResponse httpResponse = eurekaTransport.queryClient.getDelta(remoteRegionsRef.get());
    if (httpResponse.getStatusCode() == Status.OK.getStatusCode()) {
        delta = httpResponse.getEntity();
    }

    if (delta == null) {
        
        getAndStoreFullRegistry();
    } else if (fetchRegistryGeneration.compareAndSet(currentUpdateGeneration, currentUpdateGeneration + 1)) {
      
        String reconcileHashCode = "";
        if (fetchRegistryUpdateLock.tryLock()) {
            try {
                /**
                 * 这里要将从Server获取到的所有变更信息更新到本地缓存。这些变
                 * 更信来自于两类Region：本地Region与远程Region。而本地缓存也
                 * 分为两类：缓存本地Region的applications与缓存所有远程Region
                 * 的注册信息的map(key为远程Region，value为该远程Region的注册
                 * 表)
                 */
                // todo
                updateDelta(delta);
                reconcileHashCode = getReconcileHashCode(applications);
            } finally {
                fetchRegistryUpdateLock.unlock();
            }
        } 
        ...
}

增量拉取注册表的请求： GET请求 path为： apps/deltahni拜客生活常识网

然后，我们重点看一下updateDelta(delta);方法：hni拜客生活常识网

private void updateDelta(Applications delta) {
    int deltaCount = 0;
    for (Application app : delta.getRegisteredApplications()) {
        for (InstanceInfo instance : app.getInstances()) {
            Applications applications = getApplications();
            String instanceRegion = instanceRegionChecker.getInstanceRegion(instance);
            // 不是本地region,远程region
            if (!instanceRegionChecker.isLocalRegion(instanceRegion)) {
                Applications remoteApps = remoteRegionVsApps.get(instanceRegion);
                if (null == remoteApps) {
                    remoteApps = new Applications();
                    remoteRegionVsApps.put(instanceRegion, remoteApps);
                }
                applications = remoteApps;
            }

            ++deltaCount;
            // 有新增加的实例信息
            if (ActionType.ADDED.equals(instance.getActionType())) {
                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);
            // 有修改的
            } else if (ActionType.MODIFIED.equals(instance.getActionType())) {
                Application existingApp = applications.getRegisteredApplications(instance.getAppName());
                if (existingApp == null) {
                    applications.addApplication(app);
                }
                logger.debug("Modified instance {} to the existing apps ", instance.getId());

                applications.getRegisteredApplications(instance.getAppName()).addInstance(instance);

            // 有删除的
            } else if (ActionType.DELETED.equals(instance.getActionType())) {
                Application existingApp = applications.getRegisteredApplications(instance.getAppName());
                if (existingApp != null) {
                    logger.debug("Deleted instance {} to the existing apps ", instance.getId());
                    existingApp.removeInstance(instance);
                    /*
                     * We find all instance list from application(The status of instance status is not only the status is UP but also other status)
                     * if instance list is empty, we remove the application.
                     */
                    if (existingApp.getInstancesAsIsFromEureka().isEmpty()) {
                        applications.removeApplication(existingApp);
                    }
                }
            }
        }
    }
   ...
}