瞬态错误发生程序，deviceclient.sendmessage [英] Transient Error Occurer, deviceclient.sendmessage

问题描述

我有以下代码从树莓派上的传感器读取温度.

I have the following code which reads a temperature from a sensor on a raspberry pi.

该代码是异步的，如果我仅删除代码的最后一行，即发送消息的那一行，就永远不会得到异常. 我的意思是这一行:

The code is asynchronous, and if I remove ONLY the last line of the code, the one that sends the message, I never get the exception. I meant this line:

 await deviceClient.SendEventAsync(message);




 private async void InitializeSensors()
        {
            string calibrationData;
            //_periodicTimer.Dispose();
            // Inicializar el sensor bmp180
            try
            {
                _bmp180 = new Bmp180Sensor();
                await _bmp180.InitializeAsync();
                calibrationData = _bmp180.CalibrationData.ToString();   //Retorna una cadena que representa al objeto actual.
                if (_periodicTimer == null)
                {
                    _periodicTimer = new Timer(this.TimerCallback, null, 0, readingInterval);
                }
            }
            catch (Exception ex)
            {
                calibrationData = "Error de dispositivo! " + ex.Message;
            }

            var task = this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                //calibrationDataTextBlock.Text = "";
            });
        }

        public async void TimerCallback(object state)
        {
            string temperatureText;
            // Leer  datos del sensor
            try
            {
                var sensorData = await _bmp180.GetSensorDataAsync(Bmp180AccuracyMode.UltraHighResolution);
                temperatureText = sensorData.Temperature.ToString("");
                //pressureText = sensorData.Pressure.ToString("F2");
                temperatureText += "°C";
                //pressureText += "hPa - " + BitConverter.ToString(sensorData.UncompestatedPressure);
                var temperatureDataPoint = new
                {
                    deviceKey = deviceKey,
                    deviceName = deviceName,
                    temperatura = sensorData.Temperature,
                    fecha = DateTime.Now
                };
                var messageString = JsonConvert.SerializeObject(temperatureDataPoint);
                var message = new Microsoft.Azure.Devices.Client.Message(Encoding.ASCII.GetBytes(messageString));
                message.Properties["Ambiente"] = ambiente;

                ////temperatura.Text = temperatureText;
                await deviceClient.SendEventAsync(message);
            }
            catch (Exception ex)
            {
                temperatureText = "Sensor Error: " + ex.Message;
                //pressureText = "Sensor Error: " + ex.Message;
            }

            //// actualizaciones de la interfaz de usuario... deben ser invocados en el subproceso de interfaz de usuario
            var task = this.Dispatcher.RunAsync(CoreDispatcherPriority.Normal, () =>
            {
                temperatura.Text = temperatureText;
            });

        }

如果删除这些行，则可以看到传感器正在工作，因为文本框已更新为真实的温度.

If I remove the lines, I can see that the sensor is working because the Textbox is updated with the real temmperature.

仅当我取消注释sendmessage行时，我才会收到异常

Only when I uncomment the sendmessage line I get the exception

我该如何解决?

推荐答案

好的，看来您有一些线程安全问题.

OK, looks like you have some thread-safety problem.

每个 https://msdn.microsoft .com/en-us/library/microsoft.azure.devices.client.deviceclient.aspx ，(DeviceClient的)任何实例成员均不能保证是线程安全的.

Per https://msdn.microsoft.com/en-us/library/microsoft.azure.devices.client.deviceclient.aspx, Any instance members (of DeviceClient) are not guaranteed to be thread safe.

因此，使用SendEventAsync之类的东西时，照顾线程安全是您(aka开发人员)的责任.

So it is your(aka the developer) responsibility to take care of the thread-safety when using things like SendEventAsync.

在您的情况下，当您启动计时器时，框架将在每次滴答滴答过去时创建工作线程，这可能是个问题，尤其是在延迟时间为

In your case, when you kick off a timer, the framework will create worker threads each time the ticks elapsed, this could be an issue especially when the latency of

await deviceClient.SendEventAsync(message);

不确定，因此您可能会结束几个工作线程，进行相同的SendEventAsync调用.

is undeterministic, so you might end up several working threads making the same SendEventAsync calls.

一种快速简单的解决方法是在此API调用周围添加一个AutoResetEvent(locker与await不同)，如下所示，

A quick and simple fix is to add an AutoResetEvent around this API call(locker does not agree with await), something like below,

autoResetEvent.WaitOne();
await deviceClient.SendEventAsync(eventMessage);
autoResetEvent.Set();

请将此autoResetEvent设置为全局，以便由所有辅助线程共享.

Do make this autoResetEvent global so that it's shared by all the worker threads.

PS:我看到您正在尝试从某些Bmp180传感器读取数据，您可能还希望对这些调用进行线程安全.

PS: I see you're trying to read from the some Bmp180 sensor, you might want to make those calls thread-safe as well.

让我知道它是否对您有用.

Let me know if it works for you.

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