Firebase SendAllAsync返回404错误，SendAsync却正常工作

在.NET应用中使用Firebase Admin SDK通过FCM发送推送通知时，SendAsync可以正常运行，但批量发送的SendAllAsync始终返回404 Not Found错误，即使令牌有效、消息结构正确，错误信息如下：

Unknown error while making a remote service call: Response status code does not indicate success: 404 (Not Found).

相关代码如下：

public async Task SendNotificationWithJob(List<NotificationDto> input, string url = "")
{
    var data = new Dictionary<string, string>()
    {
        { "click_action", "FLUTTER_NOTIFICATION_CLICK" },
        { "url", $"{url}" }
    };

    string type = WebhookAppService.NOTIFCATION_TYPE_SUCCESS;
    var notificationTitle = input[0].Title;
    var notificationMessage = input[0].Body;

    List<Message> messages = new List<Message>();

    foreach (var notificationDto in input)
    {
        if (!string.IsNullOrEmpty(notificationDto.FirebaseToken))
        {
            var messageObj = new Message()
            {
                Notification = new FirebaseAdmin.Messaging.Notification()
                {
                    Title = notificationTitle,
                    Body = notificationMessage,
                },
                Android = new AndroidConfig()
                {
                    Notification = new AndroidNotification()
                    {
                        Title = notificationTitle,
                        Body = notificationMessage,
                        Sound = "default"
                    }
                },
                Apns = new ApnsConfig()
                {
                    Aps = new Aps()
                    {
                        Alert = new ApsAlert()
                        {
                            Title = notificationTitle,
                            Body = notificationMessage,
                        },
                        Sound = "default"
                    }
                },
                Data = data,
                Token = notificationDto.FirebaseToken,
            };

            messages.Add(messageObj);
        }
    }

    if (messages.Count == 0)
    {
        Logger.Warn("No valid tokens found for sending notifications.");
        return;
    }

    int batchSize = 100;
    int totalBatches = (messages.Count + batchSize - 1) / batchSize;

    for (int i = 0; i < totalBatches; i++)
    {
        int startIndex = i * batchSize;
        int length = Math.Min(batchSize, messages.Count - startIndex);
        var msgs = messages.GetRange(startIndex, length);

        try
        {
            Logger.Debug($"Sending request to Firebase with payload: {JsonConvert.SerializeObject(msgs, Formatting.Indented)}");
            var response = await FirebaseMessaging.DefaultInstance.SendAllAsync(msgs);
            Logger.Debug($"SendAllAsync Response: SuccessCount={response.SuccessCount}, FailureCount={response.FailureCount}");
        }
        catch (FirebaseMessagingException ex)
        {
            Logger.Error($"FirebaseMessagingException: {ex.Message}");
        }
        catch (Exception ex)
        {
            Logger.Error($"Exception: {ex.Message}");
        }
    }
}

可能的解决方案 #

• 升级Firebase Admin SDK版本：部分旧版本的SDK中SendAllAsync存在端点URL配置错误，通过NuGet将FirebaseAdmin包更新到最新稳定版，修复已知的API端点问题。
• 验证服务账号权限：确保你的服务账号已启用Firebase Cloud Messaging API，并且拥有Cloud Messaging Admin或Editor角色，避免因权限不足导致端点访问被拒绝（表现为404）。
• 检查网络/代理配置：SendAllAsync调用的是FCM批量发送端点，而SendAsync使用的是单条发送端点，若应用在代理环境下运行，需确认代理规则允许访问该批量端点。
• 确认服务账号密钥有效性：检查服务账号密钥是否过期、是否关联正确的Firebase项目，密钥配置错误可能导致SDK无法正确解析API端点地址。
• 排查批次消息内容：虽然代码中已处理空列表，但可在批次发送前添加日志，确认当前批次的msgs集合不为空，且每条消息的Token格式正确。

内容的提问来源于stack exchange，提问作者Батсүрэн