Azure Notification Hub调用GetRegistrationsByChannelAsync抛TaskCanceledException求助

我们的服务使用Azure Notification Hub推送通知，运行数月后，调用NotificationHub-Client的GetRegistrationsByChannelAsync方法时开始频繁抛出TaskCanceledException异常。

观察Azure Hub的监控数据发现，dailyMaxActiceDevices属性频繁触顶，但我们的基础订阅远未达到总注册设备的限制。该问题并非持续发生，但近期出现频率明显上升。我们没有修改过相关代码，也未在NotificationHub的官方文档或已知问题中找到对应内容，希望能得到排查思路。

异常堆栈跟踪 #

System.Threading.Tasks.TaskCanceledException: A task was canceled.
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Azure.NotificationHubs.NotificationHubClient.d__201.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Azure.NotificationHubs.NotificationHubClient.d__200.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Azure.NotificationHubs.NotificationHubClient.d__192`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

抛出异常的代码 #

if (handle != null)
{
    var registrations = await hub.GetRegistrationsByChannelAsync(handle, 100);

    foreach (RegistrationDescription registration in registrations)
    {
        if (newRegistrationId == null)
        {
            newRegistrationId = registration.RegistrationId;
        }
        else
        {
            await hub.DeleteRegistrationAsync(registration);
        }
    }
}

内容的提问来源于stack exchange，提问作者Filoteemo