Long polling with asynchronous controllers

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I'm trying to implement long polling in asp.net mvc 3 with asynchronous controllers, but my problem is that i'm unable to navigate from the page or create other ajax requests during the polling. Asynchronous controllers are a new topic to me so my questions are is it supposed to work like this or am i doing something wrong? The codes are below.

JavaScript

$(window).load(function () {
    setTimeout(function () {
        doLongPolling();
    }, 1000);
});

function doLongPolling() {
    $.post("/AsyncTest/LongPoll", null, function (data) {
        alert(data.msg);
        doLongPolling();
    });
}

C#

public class AsyncTest : AsyncController
    {
        public void LongPollAsync()
        {
            AsyncManager.OutstandingOperations.Increment();
            Thread.Sleep(20000);
            AsyncManager.Parameters["msg"] = "polling done";
            AsyncManager.OutstandingOperations.Decrement();
        }

        public ActionResult LongPollCompleted(string msg)
        {
            return this.Json(new { msg = msg });
        }
    }

Posted 29-Aug-11 1:16am

huotari

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TheyCallMeMrJames · Answer 1 · 2011-08-29T05:04:00

Hi Huotari,

Async controllers in MVC are designed to allow you to dispatch work when you need a result.

What you're describing is more likely suited to some kind of worker pattern, then to use the polling idea to check on the status of the queue/results, but not to wait for the work. Just create a thread that pushes the work to a queue and create a worker service that runs every so often to pickup work and process it.

Also, attach firebug or use your developer tools in IE and have a look at your network traffic. ASP.NET MVC uses convention, so "/AsyncTest/LongPoll" won't likely work because you didn't name your controller AsyncTestController (check for 404 on your server).

Cheers.

Peter Leow · Answer 2 · 2015-04-24T05:26:00

Solution 3

Instead of polling from the client, your should consider server push when data becoming available. Learn about SignalR[^]

Posted 24-Apr-15 5:26am

Peter Leow

hakanseysane · Answer 3 · 2015-04-24T04:40:00

C#

[NoAsyncTimeout]
public void LongPollAsync(int id)
{
     AsyncManager.OutstandingOperations.Increment();
     if (GetNew(id) != null)
     {
          AsyncManager.Parameters["msg"] = GetNew(id);
          AsyncManager.OutstandingOperations.Decrement();
     }
     else 
     {
          Thread.Sleep(2000);
          LongPollAsync(id);
          AsyncManager.OutstandingOperations.Decrement();
     }
           
}

public string GetNew(int id) {
{
    xEntities db = new xEntities();
    Notification n = db.Notification.Where(x => x.ID > id).FirstOrDefault();
    if (n != null)
    {
        return n.URL;
    }
    else { return null; }
}
catch
{
     return null; 
}
}
        public ActionResult LongPollCompleted(string msg)
        {
            return this.Json(new { msg = msg });
        }

Long polling with asynchronous controllers

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