HttpWebRequest限制？或者执行不好

Question

我正在尝试构建一个ac#console应用程序,它将监视大约3000个url(只需要知道HEAD请求返回200,不一定是内容等)

我在这里的尝试是构建一个例程来检查web URL,循环并创建每个执行例程的线程.发生的事情是如果我用<20个线程运行,它大部分时间都执行正常,但是如果我使用> 20个线程,那么一些url会超时.我尝试将Timeout增加到30秒,同样发生.我运行它的网络能够执行50个HTTP HEAD请求(ISP上的10MBIT连接),并且在执行例程时CPU和网络都运行得非常低.

当发生超时时,我在浏览器上测试相同的IP并且工作正常,我反复测试了这一点,并且在测试过程中从来没有一个"超时"网址实际超时的情况.

我想运行> 20个线程的原因是我想每5分钟执行一次这个测试,一些URL需要整整10秒(如果超时设置得更高,则更高),我想确保它能够在2-3分钟内浏览所有网址.

有没有更好的方法来检查URL是否可用,或者,我是否应该查看系统/网络中的问题.

主要

        while (rdr.Read())
        {
            Thread t = new Thread(new ParameterizedThreadStart(check_web));

            t.Start(rdr[0]);


        }

---

      static void check_web(object weburl)
      {
          bool isok;
          isok = ConnectionAvailable(weburl.ToString());
      }



      public static bool ConnectionAvailable(string strServer)
      {

          try
          {
              strServer = "http://" + strServer;
              HttpWebRequest reqFP = (HttpWebRequest)HttpWebRequest.Create(strServer);
              reqFP.Timeout = 10000;
              reqFP.Method = "HEAD";

              HttpWebResponse rspFP = (HttpWebResponse)reqFP.GetResponse();
              if (HttpStatusCode.OK == rspFP.StatusCode)
              {
                  Console.WriteLine(strServer + " - OK");
                  rspFP.Close();
                  return true;
              }
              else
              {
                  Console.WriteLine(strServer + " Server returned error..");
                  rspFP.Close();
                  return false;

              }

          }

          catch (WebException x)
          {
              if (x.ToString().Contains("timed out"))
              {
                  Console.WriteLine(strServer + " - Timed out");
              }
              else
              {
                  Console.WriteLine(x.Message.ToString());
              }

              return false;

          }

      }

Answer 1

记住,你问过.

非常糟糕的实施.

1. 不要去创建这样的线程.拥有比处理器内核更多的线程确实没什么用.额外的线程几乎只是相互竞争,特别是因为它们都运行相同的代码.

2. 您需要使用块实现.如果你抛出异常(很有可能),那么你将会泄漏资源.

3. 归还布尔的目的是什么？你在某处检查吗？在任何情况下,您的错误和异常处理都是一团糟.

   • 当您收到非200响应时,您不会显示错误代码.
   • 您将与Message属性进行比较,以确定它是否为超时.微软应该在"时间"和"外出"之间留一个空格来惹恼你.
   • 当它不是超时时,只显示Message属性,而不是整个异常,Message属性已经是一个字符串,不需要在其上调用ToString().

下一批更改

这个没有完成,我不认为,但试试这个:

public static void Main()
{
    // Don't mind the interpretation. I needed an excuse to define "rdr"
    using (var conn = new SqlConnection())
    {
        conn.Open();
        using (var cmd = new SqlCommand("SELECT Url FROM UrlsToCheck", conn))
        {
            using (var rdr = cmd.ExecuteReader())
            {
                while (rdr.Read())
                {
                    // Use the thread pool. Please.
                    ThreadPool.QueueUserWorkItem(
                        delegate(object weburl)
                            {
                                // I invented a reason for you to return bool
                                if (!ConnectionAvailable(weburl.ToString()))
                                {
                                    // Console would be getting pretty busy with all
                                    // those threads
                                    Debug.WriteLine(
                                        String.Format(
                                            "{0} was not available",
                                            weburl));
                                }
                            },
                            rdr[0]);
                }
            }
        }
    }
}

public static bool ConnectionAvailable(string strServer)
{
    try
    {
        strServer = "http://" + strServer;
        var reqFp = (HttpWebRequest)WebRequest.Create(strServer);
        reqFp.Timeout = 10000;
        reqFp.Method = "HEAD";

        // BTW, what's an "FP"?
        using (var rspFp = (HttpWebResponse) reqFp.GetResponse()) // IDisposable 
        {
            if (HttpStatusCode.OK == rspFp.StatusCode)
            {
                Debug.WriteLine(string.Format("{0} - OK", strServer));
                return true; // Dispose called when using is exited
            }

            // Include the error because it's nice to know these things
            Debug.WriteLine(String.Format(
                 "{0} Server returned error: {1}", 
                 strServer, rspFp.StatusCode));
            return false;
        }
    }
    catch (WebException x)
    {
        // Don't tempt fate and don't let programs read human-readable messages
        if (x.Status == WebExceptionStatus.Timeout)
        {
            Debug.WriteLine(string.Format("{0} - Timed out", strServer));
        }
        else
        {
            // The FULL exception, please
            Debug.WriteLine(x.ToString());
        }

        return false;
    }
}

差不多完成 - 没有经过深夜代码测试

public static void Main()
{
    using (var conn = new SqlConnection())
    {
        conn.Open();
        using (var cmd = new SqlCommand("", conn))
        {
            using (var rdr = cmd.ExecuteReader())
            {
                if (rdr == null)
                {
                    return;
                }

                while (rdr.Read())
                {
                    ThreadPool.QueueUserWorkItem(
                        CheckConnectionAvailable, rdr[0]);
                }
            }
        }
    }
}

private static void CheckConnectionAvailable(object weburl)
{
    try
    {
        // If this works, it's a lot simpler
        var strServer = new Uri("http://" + weburl);
        using (var client = new WebClient())
        {
            client.UploadDataCompleted += ClientOnUploadDataCompleted;
            client.UploadDataAsync(
                strServer, "HEAD", new byte[] {}, strServer);
        }
    }
    catch (WebException x)
    {
        Debug.WriteLine(x);
    }
}

private static void ClientOnUploadDataCompleted(
    object sender, UploadDataCompletedEventArgs args)
{
    if (args.Error == null)
    {
        Debug.WriteLine(string.Format("{0} - OK", args.UserState));
    }
    else
    {
        Debug.WriteLine(string.Format("{0} - Error", args.Error));
    }
}