C＃HTTP请求上的CPU高负载

Question

I have a bit of code that is responsible for doing http requests, there can be hundreds of threads per application that are active at a time.

Normally this works fine, however, when there are connection issues(at least I presume this to be the case) the code seems to use an excessive amount of CPU, upto 100%.

This is the piece of code in question:

 while (true)
            {
                try
                {
                    while (threadNr > newViewerCount || threadNr >= (proxies.Count))
                    {
                        Thread.Sleep(3000);
                    }

                    int sleepTimer = 4400 - (int)elapsed;
                    if (sleepTimer < 0)
                    {

                        sleepTimer = 1000;
                    }

                    Thread.Sleep(sleepTimer);

                    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(rc.url);

                    request.Method = "GET";
                    request.UserAgent = agent;
                    request.Proxy = new WebProxy(proxy);
                    request.Timeout = 5000;

                    request.CookieContainer = ck;
                    request.Headers.Add("Accept-Language", "en,en-US;q=0.7,en;q=0.3");
                    request.Accept = "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8";
                    request.Headers.Add("Accept-Encoding", "gzip, deflate");
                    request.UserAgent = userAgents[3];

                    HttpWebResponse webresponse;
                    using (webresponse = (HttpWebResponse)request.GetResponse())
                    {

                    }

                }
                catch (Exception e)
                {
                    int sl = 1500;
                    if (e.Message.Contains("timed"))
                    {
                        elapsed = 4399;
                        sl = 0;
                    }
                    Thread.Sleep(sl);
                    Console.WriteLine("Download exception:" + e.Message);

                    if (e.Message.Contains("404"))
                    {
                        Thread.Sleep(3000);
                        rc = getTokenUrl(proxy, ck); 
                    }

                    if (e.Message.Contains("forbidden"))
                    {
                        rc = getTokenUrl(proxy, ck);
                        Console.WriteLine("forbidden " + e.Message);
                    }
                }
            }

This application is running 24/7, and most of the time it's okay. But at certain times it just starts using 100% cpu. I believe this happens when the proxies are taking long to respond. Why could this possibly be the case, is there something in the code that I am overlooking that could cause the application to use 100% cpu?

Answer 1

You have a forever loop with while (true) , then there is an exception with message containing "timed", so s1 is set to zero and the loop is resumed. Elapsed is 4399, you try to sleep for 1 millisecond, which might be actually zero. So of course it is using all available CPU power possible since these conditions just keep on happening and there are no sleeps anywhere.

As was suggested, Tasks might be a better way to handle this and it's quite bad practice to have an eternal thread with no way of exiting or handling all error situations.

Also I wouldn't use e.Message as a way to determine what happened. What if the code is run on a machine that speaks French, for example?