c#多个后台工作进程相同的方法

Question

我有一个问题，当2-8个后台工作人员访问相同的方法时，会出现问题。下面是一个例子：

int threadnumber = 0;
int retries[] = new int[8];

private XmlDocument GetXML(string ApiUrl, int threadnumber)
        {
            var mySourceDoc = new XmlDocument();
            try
            {
                var httpRequest = (HttpWebRequest)WebRequest.Create(ApiUrl);
                httpRequest.Timeout = 50000;
                if (cb_Proxy.Checked == true)
                {
                    WebProxy germanserver = new WebProxy();
                    Uri newUri = new Uri("http://" + txt_Proxy.Text);
                    germanserver.Address = newUri;
                    httpRequest.Proxy = germanserver;
                }
                var response = (HttpWebResponse)httpRequest.GetResponse();
                var receiveStream = response.GetResponseStream();
                receiveStream.ReadTimeout = 150000;
                mySourceDoc.Load(receiveStream);
                receiveStream.Close();
                retries[threadnumber-1] = 1;
            }
            catch (Exception ex)
            {
                //DialogResult MessBox = MessageBox.Show("Der Server ist nicht erreichbar oder es ist ein anderes Problem mit dem Server aufgetreten. Es wird automatisch 3 mal erneut versucht. Fehlermeldung anzeigen?", "Fehler", MessageBoxButtons.YesNo, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1);
                //if (MessBox == DialogResult.Yes) MessageBox.Show(ex.Message);
                retries[threadnumber - 1]++;
                consoletext = "Fehler: " + ex.Message + "; Neuer Versuch " + retries[threadnumber - 1] + " von Url " + ApiUrl + Environment.NewLine;
                if (threadnumber == 1) workingHelper1.ReportProgress(counterhelper[0]);
                if (threadnumber == 2) workingHelper2.ReportProgress(counterhelper[1]);
                if (threadnumber == 3) workingHelper3.ReportProgress(counterhelper[2]);
                if (threadnumber == 4) workingHelper4.ReportProgress(counterhelper[3]);
                if (threadnumber == 5) workingHelper5.ReportProgress(counterhelper[4]);
                if (threadnumber == 6) workingHelper6.ReportProgress(counterhelper[5]);
                if (threadnumber == 7) workingHelper7.ReportProgress(counterhelper[6]);
                if (threadnumber == 8) workingHelper8.ReportProgress(counterhelper[7]);
                Thread.Sleep(3000);
            }
            finally
            {
                if (retries[threadnumber - 1] > 1 && retries[threadnumber - 1] <= 3) GetXML(ApiUrl, threadnumber);
                if (retries[threadnumber - 1] >= 4) retries[threadnumber] = 1;
            }
            return mySourceDoc;
}

后台工作人员使用生成的url字符串和线程编号1-8调用方法getxml。我的问题是，有时重试次数会达到5或更高。所以我认为后台工作人员有时会访问相同的变量并对其进行计数？

Answer 1

通常，允许多个线程同时操作同一对象并不是一个好主意。这肯定会导致被操纵对象的状态发生冲突。

考虑在访问和操作共享变量(即threadnumber和retries)的行上使用lock。

还要考虑调用方法的方式，因为：

1. 似乎每个工作线程都需要retries数组中的2个条目(即threadnumber和threadnumber - 1)，因此，您不能使用连续的threadnumber值调用GetXML方法，否则您将在retries数组中获得冲突。或者这可能是代码中的一个bug (下面引用)导致了这个问题。

if (retriesthreadnumber -1 >= 4) retriesthreadnumber = 1;

1. 考虑调用GetXML方法的代码，并确保它不会将相同的threadnumber分配给多个工作进程。

Answer 2

这似乎是一个合乎逻辑的失败。现在我已经调试了每个线程和实际的变量内容。所以看起来一切正常，没有任何变量可以被覆盖。

private XmlDocument GetXML(string ApiUrl, int threadnumber)
    {
        object thislock = new object();
        lock (thislock)
        {
            var mySourceDoc = new XmlDocument();
            try
            {
                var httpRequest = (HttpWebRequest)WebRequest.Create(ApiUrl);
                httpRequest.Timeout = 50000;
                if (cb_Proxy.Checked == true)
                {
                    WebProxy proxy = new WebProxy();
                    Uri newUri = new Uri("http://" + txt_Proxy.Text);
                    proxy.Address = newUri;
                    httpRequest.Proxy = proxy;
                }
                var response = (HttpWebResponse)httpRequest.GetResponse();
                var receiveStream = response.GetResponseStream();
                receiveStream.ReadTimeout = 150000;
                mySourceDoc.Load(receiveStream);
                receiveStream.Close();
                retries[threadnumber - 1] = 1;
            }
            catch (Exception ex)
            {
                retries[threadnumber - 1]++;
                if (retries[threadnumber - 1] == 4)
                {
                    consoletext = "Endgültiger Abbruch von Url " + ApiUrl + Environment.NewLine;
                    writeLog("Worker: " + threadnumber + " Endgültiger Abbruch von Url " + ApiUrl);
                }
                else
                {
                    consoletext = "Fehler: " + ex.Message + "; Neuer Versuch " + retries[threadnumber - 1] + " von Url " + ApiUrl + Environment.NewLine;
                    writeLog(ex.Message + "; Versuch: " + retries[threadnumber - 1] + " Thread: " + threadnumber + " URL: " + ApiUrl);
                }
                //DialogResult MessBox = MessageBox.Show("Der Server ist nicht erreichbar oder es ist ein anderes Problem mit dem Server aufgetreten. Es wird automatisch 3 mal erneut versucht. Fehlermeldung anzeigen?", "Fehler", MessageBoxButtons.YesNo, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1);
                //if (MessBox == DialogResult.Yes) MessageBox.Show(ex.Message);

                if (threadnumber == 1) workingHelper1.ReportProgress(counterhelper[0]);
                if (threadnumber == 2) workingHelper2.ReportProgress(counterhelper[1]);
                if (threadnumber == 3) workingHelper3.ReportProgress(counterhelper[2]);
                if (threadnumber == 4) workingHelper4.ReportProgress(counterhelper[3]);
                if (threadnumber == 5) workingHelper5.ReportProgress(counterhelper[4]);
                if (threadnumber == 6) workingHelper6.ReportProgress(counterhelper[5]);
                if (threadnumber == 7) workingHelper7.ReportProgress(counterhelper[6]);
                if (threadnumber == 8) workingHelper8.ReportProgress(counterhelper[7]);
                Thread.Sleep(3000);
            }
            finally
            {
                if (retries[threadnumber - 1] > 1 && retries[threadnumber - 1] <= 3) GetXML(ApiUrl, threadnumber);
                //if (retries[threadnumber - 1] >= 4) retries[threadnumber - 1] = 1;
                else retries[threadnumber - 1] = 1;
            }
            return mySourceDoc;
        }
    }