NotificationControllerV2：notifications/v2：实现长轮循，监听配置变更、返回，结束长轮循

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目录

概 述

NotificationControllerV2实现了ReleaseMessageListener，具体什么时候注册的监听器请参考：ConfigServiceAutoConfiguration

/**
	   * 监听器注册，namespaces变更后接收消息
	   * @return
	   */
    @Bean
    public ReleaseMessageScanner releaseMessageScanner() {
      ReleaseMessageScanner releaseMessageScanner = new ReleaseMessageScanner();
      //0. handle release message cache
      releaseMessageScanner.addMessageListener(releaseMessageServiceWithCache);
      //1. handle gray release rule
      releaseMessageScanner.addMessageListener(grayReleaseRulesHolder);
      //2. handle server cache
      releaseMessageScanner.addMessageListener(configService);
      releaseMessageScanner.addMessageListener(configFileController);
      //3. notify clients
      releaseMessageScanner.addMessageListener(notificationControllerV2);
      releaseMessageScanner.addMessageListener(notificationController);
      return releaseMessageScanner;
    }

进入主流程2.1客户端请求，ConfigSerivce通知配置变更，这里是利用Spring DeferredResult实现长轮循

@GetMapping
  public DeferredResult<ResponseEntity<List<ApolloConfigNotification>>> pollNotification(
      @RequestParam(value = "appId") String appId,
      @RequestParam(value = "cluster") String cluster,
      @RequestParam(value = "notifications") String notificationsAsString,
      @RequestParam(value = "dataCenter", required = false) String dataCenter,
      @RequestParam(value = "ip", required = false) String clientIp) {
    List<ApolloConfigNotification> notifications = null;
 
    try {
    	//因为一个客户端可以订阅过个namespace所以是list
      notifications =
          gson.fromJson(notificationsAsString, notificationsTypeReference);
    } catch (Throwable ex) {
      Tracer.logError(ex);
    }
 
    if (CollectionUtils.isEmpty(notifications)) {
      throw new BadRequestException("Invalid format of notifications: " + notificationsAsString);
    }

DeferredResultWrapper deferredResultWrapper = new DeferredResultWrapper(bizConfig.longPollingTimeoutInMilli());
    //namespaces集合
    Set<String> namespaces = Sets.newHashSet();
    //客户端通知的map，key：namespaces名；value：通知编号
    Map<String, Long> clientSideNotifications = Maps.newHashMap();
    //key：namespaces名
	  //过滤ApolloConfigNotification
    Map<String, ApolloConfigNotification> filteredNotifications = filterNotifications(appId, notifications);
 
    for (Map.Entry<String, ApolloConfigNotification> notificationEntry : filteredNotifications.entrySet()) {
      String normalizedNamespace = notificationEntry.getKey();
      ApolloConfigNotification notification = notificationEntry.getValue();
      //添加到namespaces里
      namespaces.add(normalizedNamespace);
      //添加通知客户端map
      clientSideNotifications.put(normalizedNamespace, notification.getNotificationId());
      // 记录名字被归一化的 Namespace 。因为，最终返回给客户端，使用原始的 Namespace 名字，否则客户端无法识别。
      if (!Objects.equals(notification.getNamespaceName(), normalizedNamespace)) {
        deferredResultWrapper.recordNamespaceNameNormalizedResult(notification.getNamespaceName(), normalizedNamespace);
      }
    }

if (CollectionUtils.isEmpty(namespaces)) {
      throw new BadRequestException("Invalid format of notifications: " + notificationsAsString);
    }
	//组装Watch key集合
    Multimap<String, String> watchedKeysMap =
        watchKeysUtil.assembleAllWatchKeys(appId, cluster, namespaces, dataCenter);
	//生成watch key 集合
    Set<String> watchedKeys = Sets.newHashSet(watchedKeysMap.values());

deferredResultWrapper
          .onTimeout(() -> logWatchedKeys(watchedKeys, "Apollo.LongPoll.TimeOutKeys"));
	//注册结束事件
    deferredResultWrapper.onCompletion(() -> {
      //unregister all keys
		//移除watch key+deferredResultWrapper出deferredResults
      for (String key : watchedKeys) {
        deferredResults.remove(key, deferredResultWrapper);
      }
      logWatchedKeys(watchedKeys, "Apollo.LongPoll.CompletedKeys");
    });

for (String key : watchedKeys) {
      this.deferredResults.put(key, deferredResultWrapper);
    }
     entityManagerUtil.closeEntityManager();
	//获取最新的ApolloConfigNotification集合
    List<ApolloConfigNotification> newNotifications =
        getApolloConfigNotifications(namespaces, clientSideNotifications, watchedKeysMap,
            latestReleaseMessages);
//	若有更新直接设置结果
    if (!CollectionUtils.isEmpty(newNotifications)) {
      deferredResultWrapper.setResult(newNotifications);
    }
 
    return deferredResultWrapper.getResult();
  }

``
 我们重点看一下getApolloConfigNotifications()：获取最新的ApolloConfigNotification集合:
 


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小结

NotificationControllerV2：notifications/v2：实现长轮循，监听配置变更、返回，结束长轮循

参考资料和推荐阅读

1.链接: 参考资料.