GetRequestStream throws Timeout exception randomly

问题:

After googling for couple of days, I really cannot solve described issue. Hope here will find a solution

I'm using attached code when calling WCF service on the same server. I get Timeout error randomly in call WebReq.GetRequestStream()

When I'm check netstat I see that connection remains open, so probably is there a problem, but I don't know how to solve it

       //request inicialization
        HttpWebRequest WebReq = (HttpWebRequest)WebRequest.Create(url);
        WebReq.Method = "POST";
        WebReq.ContentType = "application/json; charset=utf-8";
        WebReq.ContentLength = buffer.Length;

        WebReq.Proxy = null;
        WebReq.KeepAlive = false; //also tried with true
        WebReq.AllowWriteStreamBuffering = false; //also tried with true

        //this produces an error
        using (Stream PostData = WebReq.GetRequestStream())
        {
            PostData.Write(buffer, 0, buffer.Length);
            PostData.Close();
        }

         //open and read response
         HttpWebResponse WebResp = (HttpWebResponse)WebReq.GetResponse();
         Stream Answer = WebResp.GetResponseStream();
         StreamReader _Answer = new StreamReader(Answer);

         WebResp.Close();

         //return string
         return _Answer.ReadToEnd();

Timeout is thrown mostly after some 10 seconds of idle time, but also after five or so requests in the row. Really cannot find a pattern.

What could be wrong with this code? Is there any other (better) way for calling WCF service?

回答1:

I don't know that it's definitely responsible for the problem, but you're only closing the web response if it doesn't throw an exception, and you're never closing the response stream. Use using statements:

using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
using (StreamReader reader = new StreamReader(response.GetResponseStream()))
{
    return reader.ReadToEnd();
}

This could well explain the problem, as if you leave a response open it will keep the connection to the web server open - which means connection pooling then can't use that connection.

回答2:

I had this same issue, adding a call to HttpWebRequest.Abort() seemed to fix it.

回答3:

Because this is really strange behaviour I would like to know if there are any other ways to call WCF service, hosted on same IIS server. I also thing, that creating TCP connection for that kind of calls in not really optimized and all other approaches should be much faster.

回答4:

The first thing to keep in mind is to review the URI, parameters and headers being sent, specifically:

• Reserved characters. Send reserved characters by the URI can bring problems ! * ' ( ) ; : @ & = + $ , / ? # []
• URI Length: You should not exceed 2000 characters
• Length headers: Most web servers do limit size of headers they accept. For example in Apache default limit is 8KB.

Keep in mind that if you want to send data from a longer length is recommended to send in the body of the message.