NodeJS Queue performing delayed HTTP Request are weird - node.js

Question

Dear helpful people in the internet,
i started to write an HTTP Queue. I have a Request Class, which works if I use it without context, but with my queue active, my http requests wont work. I can't figure out why.
var t = new Request('s','s', function(){});
t.perform();
When i perform the request like this in any file. It works. But when i use it with my queue (index.js,L19 to L22) no request is performed. The function Request.perform() were executed, but the HTTP-Request isn't there.
Sorry for my english, I'm not native ^^
index.js
const http = require('http');
const https = require('https');
const {Request} = require('./classes/Request');
const queue = require('./queue.js');
queue.setCallbackFunction(performRequest);
function performRequest(request){
console.log("2");
request.perform();
}
var req = new Request('','', function(response,body){
console.log(JSON.stringify(response) + " :: " + body);
});
queue.add(req);
queue.js
var queue = [];
var ratelimits = [];
module.exports.add = function(request){
queue.push(request);
run_queue();
}
module.exports.setCallbackFunction = function(cb){
call = cb;
}
module.exports.setRateLimits = function(ratelimitings){
ratelimits = [];
for(var z in ratelimitings){
var x = ratelimitings[z];
var data = {};
data.max = x[0];
data.time = x[1];
data.count = 0;
ratelimits[x[1]] = data;
}
}
function run_queue(){
var q;
if(queue.length > 0){
q = run_request(queue[0]);
while (q == true) {
queue.shift();
if(queue.length > 0)
q = run_request(queue[0]);
}
}
}
function run_request(request){
for(var z in ratelimits){
var x = ratelimits[z];
if(x.max <= x.count){
return false;
}
}
for(var z in ratelimits){
var x = ratelimits[z];
if(x.count === 0){
setTimeout(function(z){
console.log(JSON.stringify(x));
ratelimits[z].count = 0;
run_queue();
},z,z);
}
x.count++;
//console.log(JSON.stringify(x));
}
//DO REQUEST
console.log("1")
call(request);
return true;
}
Request.js
exports.Request = class{
constructor(host,path,cb){
this.path = path;
this.cb = cb;
this.host = host
}
perform(){
console.log("3");
var https = require('https');
var options = {
host: 'www.example.com',
path: '/'
};
var callback = function(response) {
//HERE THIS GETS NEVER CALLED BECAUSE OF WHATEVER WHILE ITS IN THE QUEUE
var str = '';
//another chunk of data has been recieved, so append it to `str`
response.on('data', function (chunk) {
str += chunk;
});
//the whole response has been recieved, so we just print it out here
response.on('end', function () {
console.log(str);
});
}
https.request(options, callback).end();
}
}
All 3 console.logs get printed, but the Request Callback Never gets called.

Answer 1

The problem is caused by function run_queue:
function run_queue(){
var q;
if(queue.length > 0){
q = run_request(queue[0]);
while (q == true) {
queue.shift();
if(queue.length > 0)
q = run_request(queue[0]);
}
}
}
After run_request() is executed successfully (HTTP request is sent), queue.shift() is called immediately, which means the req object you just added into the queue is removed from queue array and qualified for Garbage Collection. As one HTTP request/response will normally cost a few milliseconds, it is very likely that before response is retrieved, the req object is GCed (destroyed). Thus, no callback will be invoked, as the HTTP connection does not exist any more.
To change queue but keep req object from GC, you need to save it somewhere else, such as a temporary array (the infinite loop bug is also fix in following code):
var tmp = [];
function run_queue(){
var q;
if(queue.length > 0){
q = run_request(queue[0]);
while (q == true) {
tmp.push(queue.shift());
if(queue.length > 0) {
q = run_request(queue[0]);
} else {
q = false;
}
}
}
}
Please note the above code is only for demo. In production code, you need to manage the tmp array -- when one request is done, it needs to be removed from tmp. Otherwise, tmp array will keep growing...