Killing Ajax requests

[sridhar lakka]

Hi All,

Thanks in advance.

suppose if there are multiple requests are fired with ajax and most of them are pending.
After some time suppose if i want to abort all those requests then what should I do.
Means how to maintain a pool of requests which are waiting since long and How to kill all those request.
Do we have any thing like session.invalidate() and sessionListener kind.

Please help me..

Regards
Sree

[Anirvan Majumdar]

Hi,

firstly are you sure you can fire concurrent AJAX requests to the server? As far as I know, AJAX calls too happen in a sequential manner. If you fire a request before a previous one has completed, then the previous one automatically gets suppressed (something like if you click on two different links one after the other, then the second links call gets rendered).

I am not too sure whether you can do a check on open AJAX calls as well. Not atleast through JavaScript, since there's no multi-threading mechanism to do so, and the script execution halts at the point where you make an AJAX call. Maybe you can think of killing the request at the server side by multi-threading and returning a status through response if the call doesn't get served within a particular duration of time.

[Stan James]

You can run multiple XMLHttpRequest calls at the same time if you set the asynchronous flag to true on the call. You have to go to some effort to get the proper callback on the proper response. I got this off the net:

function callXmlRequest( uri, callback, onError )
{
   try
   {
      var xmlRequest = getXMLHttpRequest( )
      
      function callbackClosure(){
         if (xmlRequest.readyState == 4) 
         {
            if (xmlRequest.status == 200) 
                callback(xmlRequest.responseText);
            else 
                alert("Error calling server:\n" 
                    + xmlRequest.status + ":\t" 
                    + xmlRequest.statusText + "\n" 
                    + xmlRequest.responseText);             
          }
      }
  
      xmlRequest.open( "GET", uri, true );
      xmlRequest.onreadystatechange = callbackClosure;
      xmlRequest.send( );
   }
   catch( e )
   {
      if( onError )
         onError( e )
   }
}

As far as cancelling requests, you cannot send a signal to the server to say "stop processing this request". You can decide to ignore the response. That logic would be very much dependent on what you're doing.
[ September 05, 2007: Message edited by: Stan James ]

[Eric Pascarello]

Look into the abort() method

Eric

[Valentin Crettaz]

firstly are you sure you can fire concurrent AJAX requests to the server?

Well, that's the whole purpose of Ajax in the first place.

I am not too sure whether you can do a check on open AJAX calls as well. Not atleast through JavaScript, since there's no multi-threading mechanism to do so, and the script execution halts at the point where you make an AJAX call.

Of course it's possible. When the request has been sent, the browser will call the onreadystatechange callback of the XHR object to provide some feedback about how the request is progressing. This is where you can decide whether to call abort() on the XHR object to kill the request.

[sridhar lakka]

Hi Valentin,
Thanks a lot for your response.
I got some idea on how to do, however I have to kill the multiple requests of single user to be killed at a time.
I have some idea on the same could you please help me, Is it possible or not?
At javascript I am creating an array which will have AjaxRequest() class objects and I am able to print those objects in that array,however I don�t know how to fire a method to kill or destroy that object.

Regards,
Sree

[Valentin Crettaz]

you can iterate over the array and call abort() on each object and then delete the object altogether.

var userXHR = ...; //array containing the XHR objects
 
//at some point in the code
for (var i = 0; i < userXHR.length; i++) {
  userXHR[i].abort();
  delete userXHR[i];
}

[sridhar lakka]

Thanks a lot.
Could you please tell me what is XHRObject, we are using AjaxRequest class.
Regards,
Sree

[Ulf Dittmer]

Could you please tell me what is XHRObject

XMLHttpRequest