CODEWITHSUNDEEP
javascriptangularjs
Niek Jonkman
Niek Jonkman

Reputation: 1056

Long polling issues in angular

Recently I have been struggling with Long polling in angularJS. I had this code working in the past:

function longPulling(){

$.ajax({
    type: "GET", 
    url: "someScript.php", 

    async: true, 
    cache: false, 
    timeout:50000, 

    success: function(data){ 
        appendMessage("new", data); 
        setTimeout(
            longPulling, 
            1000 
        );
    },
    error: function(XMLHttpRequest, textStatus, errorThrown){
        appendMessage("error", textStatus + " (" + errorThrown + ")");
        setTimeout(
            longPulling, 
            15000); 
    }
});
};

$(document).ready(function(){
   longPulling();
});

And this worked when I used some php script. Next I wanted this to work in angular and I created the following:

angular.module("WIMT").controller('overviewController', function ($scope,$interval,$http){

$scope.longPolling = function(){
    $http({
        method: 'GET',
        url: '/someUrl'
    }).then(function successCallback(response) {
        $interval(function(){
            $scope.longPolling();
        },5000)
    }, function errorCallback(response) {
        $interval(function(){
            $scope.longPolling();
        },5000)
    });
};

$scope.longPolling();

}

For testing purposes I did not include a url and checked the console for 404 errors. I used $interval to set 5 second intervals, the problem with this was that it created multiple threads running the interval (looked like it, correct me if im wrong). So I browsed some StackOverflow topics and tried to apply one of the solutions to my code, looking like this:

angular.module("WIMT").controller('overviewController', function ($scope,$interval,$http){
var promise;

$scope.start = function() {
    $scope.stop();

    promise = $interval( $scope.longPolling(), 5000);
};

$scope.stop = function() {
    $interval.cancel(promise);
};

$scope.longPolling = function(){
    $http({
        method: 'GET',
        url: '/someUrl'
    }).then(function successCallback(response) {
        $scope.start();
    }, function errorCallback(response) {
        $scope.start();
    });
};

$scope.start();

}

The problem with this one is that the interval just doesn't work, it lookes likes its just a regular recursive method that runs thousands of times per seconds. I need to find a solution where I can perform long polling to some url withouth duplicate threads. How can I do this?

Upvotes: 0

Views: 285

Answers (1)

Henrique Barcelos
Henrique Barcelos

Reputation: 7900

Omit the parenthesis and you are fine:

promise = $interval( $scope.longPolling, 5000);

The parenthesis mean "call this function right the way". What $interval expects is a callback, not the result of the function call.

Upvotes: 1

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