Getting "The remote server returned an error: (503) Server Unavailable" on ttp://toolbarqueries.google.com/search?q=info:(domainName)

I am trying to create a windows service. The开发者_开发技巧 purpose of service is to pick up urls from a database and check their page rank from google. The purpose is to catch any one faking their page ranks. I found some code at http://www.codeproject.com/KB/aspnet/Google_Pagerank.aspx and used it.

Now here is the code

  public static int GetPageRank()
    {

        string file = "http://toolbarqueries.google.com/search?q=info:codeproject.com";
        try
        {
            //Request PR from Google



            WebRequest request = WebRequest.Create(file);
            WebResponse response = request.GetResponse();

            StreamReader reader = new StreamReader(response.GetResponseStream());
            string data = reader.ReadToEnd();

            reader.Close();
            response.Close();

            //Parse PR from string
            int pageRank = -1;
            if (data.IndexOf(':') != -1)
            {
                data = data.Substring(data.LastIndexOf(':') + 1);
            }

            int.TryParse(data, out pageRank);

            return pageRank;
        }
        catch (Exception ex)
        {

            MessageBox.Show(ex.Message);
            return -1;
        }
    }

Now what is happening is this when this method is called after some tries like 100 tries i start getting following exception. "The remote server returned an error: (503) Server Unavailable". I have done some research and i have seen a related question on stack overflow as well. Apparently google stops serving requests if to many of them originate from a same ip. Are there any work arounds to it that will enable me to check several thousand pageranks in say two hours or three hours.

Are there any work arounds to it that will enable me to check several thousand pageranks in say two hours or three hours[?]

Nope. You're simply requesting too much data. There might be a JSON or XML API to get batch responses, but I am not aware of any from Google.

Finally what we did was get proxies from a proxy provider and use them. Had to use a semaphore so that all the threads would be assigned a new proxy while ensuring that a proxy is not used more that 3 times a minute and proxies are rotated in circular sequential manner. There is no other work around to this.