实时传播 Remote Config 更新

Cloud Functions for Firebase 提供的 Remote Config 后台函数触发功能与 FCM 结合使用,您可以实时传播 Remote Config 更新。在此情形下,您需要创建一个函数,使其在您通过信息中心或 API 发布或回滚远程配置模板时触发。模板更新会触发此函数发送 FCM 消息,告知客户端它们当前的配置已过时,下次应从服务器提取配置:

显示通过 Cloud Functions 触发 FCM 提醒的 Remote Config 更新的图表

本文档的其余部分将逐步介绍实时传播 Remote Config 更新的操作。

为客户端应用实例订阅 FCM 主题

如需向大量客户端应用实例(例如整个用户群)发送 FCM 消息,主题消息传递是最有效的机制。 需要接收实时 Remote Config 更新的每个应用实例都必须订阅一个主题名称,例如 PUSH_RC

Swift

extension AppDelegate : MessagingDelegate {
    func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
        messaging.subscribe(toTopic: "PUSH_RC") { error in
            print("Subscribed to PUSH_RC topic")
        }
    }
}
    

Objective-C

- (void)messaging:(FIRMessaging *)messaging didReceiveRegistrationToken:(NSString *)fcmToken {
    [[FIRMessaging messaging] subscribeToTopic:@"PUSH_RC" completion:^(NSError * _Nullable error) {
        NSLog(@"Subscribed to PUSH_RC topic");
    }];
}
    

Android

@Override
public void onNewToken(String s) {
    FirebaseMessaging.getInstance().subscribeToTopic("PUSH_RC");
}
    

创建一个函数以在模板更新时发送 FCM ping

您可以触发一个函数来响应 Remote Config 事件(包括发布新的配置版本或回滚到旧版本)。 如需实时传播模板更新,请创建一个函数来侦听模板发布事件,然后在函数中使用 FCM Admin SDK 向客户端应用实例发送静默 ping:

exports.pushConfig = functions.remoteConfig.onUpdate(versionMetadata => {
  // Create FCM payload to send data message to PUSH_RC topic.
  const payload = {
    topic: "PUSH_RC",
    data: {
      "CONFIG_STATE": "STALE"
    }
  };
  // Use the Admin SDK to send the ping via FCM.
  return admin.messaging().send(payload).then(resp => {
    console.log(resp);
    return null;
  });
});

此函数会设置 CONFIG_STATE 参数,然后将其作为 FCM 消息的数据载荷发送给所有订阅了 PUSH_RC 主题的客户端。

在客户端上设置 Remote Config 状态

在应用的共享偏好设置中,上一步中所示的数据载荷始终会将 CONFIG_STATE 设置为 STALE。它表示由于创建了更新后的新模板(该模板的发布触发了相应函数),之前存储在应用上的 Remote Config 模板已经过时。请更新您的通知处理程序并针对这种状况进行测试:

Swift

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable: Any],
                 fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

    if (userInfo.index(forKey: "CONFIG_STATE") != nil) {
        print("Config set to stale")
        UserDefaults.standard.set(true, forKey:"CONFIG_STALE")
    }

    completionHandler(UIBackgroundFetchResult.newData)
}
    

Objective-C

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {

    if (userInfo[@"CONFIG_STATE"]) {
        NSLog(@"Config set to stale");
        [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"CONFIG_STALE"];
    }

    completionHandler(UIBackgroundFetchResultNewData);
}
    

Android

@Override
public void onMessageReceived(RemoteMessage remoteMessage) {
    if (remoteMessage.getData().containsKey("CONFIG_STATE")) {
        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(this);
        sharedPreferences.edit().putBoolean("CONFIG_STALE", true).apply();
    }
}
    

在应用启动时提取 Remote Config 更新

Swift

func fetchConfig() {
  welcomeLabel.text = remoteConfig[loadingPhraseConfigKey].stringValue

  var expirationDuration = 3600
  // If your app is using developer mode, expirationDuration is set to 0, so each fetch will
  // retrieve values from the service.
  if remoteConfig.configSettings.isDeveloperModeEnabled || UserDefaults.standard.bool(forKey: "CONFIG_STALE") {
    expirationDuration = 0
  }

  remoteConfig.fetch(withExpirationDuration: TimeInterval(expirationDuration)) { (status, error) -> Void in
    if status == .success {
      print("Config fetched!")
      self.remoteConfig.activateFetched()
    } else {
      print("Config not fetched")
      print("Error: \(error?.localizedDescription ?? "No error available.")")
    }
    self.displayWelcome()
  }
}
    

Objective-C

- (void)fetchConfig {
    self.welcomeLabel.text = self.remoteConfig[kLoadingPhraseConfigKey].stringValue;

    long expirationDuration = 3600;
    // If your app is using developer mode, expirationDuration is set to 0, so each fetch will
    // retrieve values from the Remote Config service.
    if (self.remoteConfig.configSettings.isDeveloperModeEnabled || [[NSUserDefaults standardUserDefaults] boolForKey:@"CONFIG_STALE"]) {
        expirationDuration = 0;
    }

    [self.remoteConfig fetchWithExpirationDuration:expirationDuration completionHandler:^(FIRRemoteConfigFetchStatus status, NSError *error) {
        if (status == FIRRemoteConfigFetchStatusSuccess) {
            NSLog(@"Config fetched!");
            [self.remoteConfig activateFetched];
            [[NSUserDefaults standardUserDefaults] setBool:NO forKey:@"CONFIG_STALE"];
        } else {
            NSLog(@"Config not fetched");
            NSLog(@"Error %@", error.localizedDescription);
        }
        [self displayWelcome];
    }];
}
    

Android

private void fetchWelcomeMessage() {
    mWelcomeTextView.setText(mFirebaseRemoteConfig.getString("loading_phrase"));

    long cacheExpiration = 43200; // 12 hours in seconds.
    // If your app is using developer mode or cache is stale, cacheExpiration is set to 0,
    // so each fetch will retrieve values from the service.
    if (mFirebaseRemoteConfig.getInfo().getConfigSettings().isDeveloperModeEnabled() ||
            mSharedPreferences.getBoolean("CONFIG_STALE", false)) {
        cacheExpiration = 0;
    }

    mFirebaseRemoteConfig.fetch(cacheExpiration)
            .addOnCompleteListener(this, new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    if (task.isSuccessful()) {
                        Toast.makeText(MainActivity.this, "Fetch Succeeded",
                                Toast.LENGTH_SHORT).show();

                        // After config data is successfully fetched, it must be activated before newly fetched
                        // values are returned.
                        mFirebaseRemoteConfig.activateFetched();
                    } else {
                        Toast.makeText(MainActivity.this, "Fetch Failed",
                                Toast.LENGTH_SHORT).show();
                    }
                    mWelcomeTextView.setText(mFirebaseRemoteConfig.getString("welcome_message"));
                }
            });
}
    

最后,在您的应用中添加逻辑以在 CONFIG_STATESTALE 时强制从网络中提取 Remote Config(忽略本地存储空间)。如果您的应用过于频繁地从网络中进行提取,则可能会受到 Firebase 的限制。请参阅限制