Async HTTP call AngularJS

Async HTTP call AngularJS.html

<div class="col-md-6 col-sm-6 col-xs-12">
    <select 
        ng-change="changeCluster(1)"
        ng-options="s.cluster_id as s.cluster_title for s in parentLevel" 
        ng-model="currentCluster.co_sub_cluster">
    </select>
</div>

<div class="col-md-6 col-sm-6 col-xs-12">
    <div class="clearfix">
        <select 
            ng-change="changeCluster(2)"
            ng-options="s.cluster_id as s.cluster_title for s in childLevel" 
            ng-model="currentCluster.sub_cluster">
        </select>
    </div>
</div>


<script>
app.controller('clusterCrtl', function ($scope, $http, $timeout, $q) {

    $scope.EditCluster = function(){
       
        this.getCluster(0).then(function(response){
            $scope.parentLevel = response;
        });
        this.getCluster(coSubClusterId).then(function(response){
            $scope.childLevel = response;
        });
        this.getCluster(subClusterId).then(function(response){
            $scope.grandChildLevel = response;
        });
    };
    
    $scope.getCluster = function(id){
        var deferred = $q.defer();

        $http.get('<?php echo URL_root; ?>ws/ws_cluster.php', {
            params:{
                task: 10,
                parent: id,
            }
        }).success(function (response) {          
            var data = response.record;
            deferred.resolve(data);
        });
        return deferred.promise;
    };

});
</script>