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Posted 31 Jul 2011

Tweaking WCF to build highly scalable async REST API

, 31 Jul 2011 CPOL
You can build async REST API using WCF but due to some bug in WCF implementation it does not scale as you would want it to. Here's my journey with Microsoft's WCF team to explore the problem and find the right fix.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Net;

namespace WcfAsyncRestApi
    /// <summary>
    /// Summary description for AsyncHandler
    /// </summary>
    public class AsyncHandler : IHttpAsyncHandler

        public bool IsReusable
                return false;

        public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
            HttpWebRequest request = WebRequest.Create(context.Request["url"]) as HttpWebRequest;
            return request.BeginGetResponse(cb, new MyState { Context = context, Request = request });

        public void EndProcessRequest(IAsyncResult result)
            var state = result.AsyncState as MyState;
            var webResponse = state.Request.EndGetResponse(result);
            var stream = webResponse.GetResponseStream();
            byte[] buffer = new byte[8000];
            int size = 0;

            state.Context.Response.AddHeader("Content-Type", "text/plain");
                size = stream.Read(buffer, 0, 8000);
                if (size > 0)
                    state.Context.Response.OutputStream.Write(buffer, 0, size);
            } while (size > 0);

        public void ProcessRequest(HttpContext context)
            throw new NotImplementedException();

    class MyState
        public HttpContext Context;
        public HttpWebRequest Request;

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