For some reason KendoUI DataSource does not allow to access current ajax request. Indeed, it seems quite natural to have a way to cancel running request.

To achieve a desired effect we have made a small set of changes in the RemoteTransport class:

var RemoteTransport_setup = kendo.RemoteTransport.fn.setup;

kendo.RemoteTransport.fn.setup = function()
{
  var that = this,
      options = RemoteTransport_setup.apply(that, arguments),
      beforeSend = options.beforeSend;

  options.beforeSend = functions(request, options)
  {
    that.abort();

    that._request = request;

    if (beforeSend && (beforeSend.apply(this, arguments) === false))
    {
      that._request = null;

      return false;
    }

    request.always(function() { that._request = null; });
  } 

  return options;
}

kendo.RemoteTransport.fn.request = function()
{
  return this._request;
}

kendo.RemoteTransport.fn.abort = function()
{
  var request = this._request;

  if (request)
  {
    this._request = null;
    request.abort();
  }
}

These changes allow to get an ajax request instance: grid.dataSource.request(), or to cancel a request grid.dataSource.abort().