.NET HttpClient sendAsync() Timeout on second request specifically - asp.net

Question

I been working on a proxy-like controller on ASP.NET, it takes URL from incoming request and uses HttpClient to call the URL, then return the file.
This proxy-like controller work like this:
Works fine when executing one request
Works fine when executing multiple requests,those responses have content-type of "application/json" and "xml"
Request Time-out on 2nd request and Task Cancelled when executing 4 requests, those responses have content-type of "image/png". Like following:
(These 4 request are being sent to controller almost at the same time).
Request 1 - start at 0s , finished at 1s
Request 2 - start at 1s ,Time out and exception throw at 11:00(Time out is 10s), server hangs until timeout
Request 3 - start at 11s , finished at 12s
Request 4 - start at 12s , finsihed at 13s
Please Ignore the POST Situation
Controller
public async Task<FileStreamResult> Proxy(string method, string url, string data = "")
{
myHttpClient client = new myHttpClient();
Tuple<MemoryStream,string> result = await client.Proxy(this.Request, method, url).ConfigureAwait(false);
return File(result.Item1,result.Item2); //file stream and file type
}
HttpClient
public class myHttpClient
{
private static HttpClient _httpClient;
static myHttpClient()
{
if (_httpClient == null) {
_httpClient = new HttpClient(new HttpClientHandler() { UseDefaultCredentials = true });
_httpClient.Timeout = TimeSpan.FromSeconds(7);
Log ocLog = new Log();
ocLog.Write("init client " + ServicePointManager.DefaultConnectionLimit ,false);
}
}
public async Task<Tuple<MemoryStream, string>> Proxy(HttpRequestBase contextRequest, string method, string url)
{
var request = new HttpRequestMessage();
request.RequestUri = new Uri("http://localhost" + url);
if (method == "GET")
{
request.Method = HttpMethod.Get;
request.Content = null;
}
else if (method == "POST")
{
request.Method = HttpMethod.Post;
}
//copy request header from context.Request
foreach (string headerName in contextRequest.Headers)
{
string[] headerValues = contextRequest.Headers.GetValues(headerName);
if (!request.Headers.TryAddWithoutValidation(headerName, headerValues))
{
request.Content.Headers.TryAddWithoutValidation(headerName, headerValues);
}
}
try
{
using (HttpResponseMessage response = await _httpClient.SendAsync(request).ConfigureAwait(false))
{
if (response.IsSuccessStatusCode)
{
var contentBytes = await response.Content.ReadAsByteArrayAsync().ConfigureAwait(false);
MemoryStream ms = new MemoryStream(contentBytes);
return new Tuple<MemoryStream, string>(ms, response.Content.Headers.ContentType.ToString());
}
else
{
return null;
}
}
}
catch (Exception ex)
{
throw ex;
}
}
}
What have i tried
Checking ServicePointManager.DefaultConnectionLimit. It is very large.
Use System.net.WebRequest library instead of HttpClient, still the same.

Answer 1

The problem has been solved by setting the "Maximum Process Workers" of the application pool to 3. It did the trick