Why node.js server takes longer for each new set of requests #1179
Description
This regards Node.js versions 9+
I have a simple Node.js Express server running, I issued this command history:
round 1:
$ node server.js
$ node /Users/alexamil/perf.test.js
passed in these millis: 3405
$ node /Users/alexamil/perf.test.js
passed in these millis: 4010
$ node /Users/alexamil/perf.test.js
passed in these millis: 5290
$ node /Users/alexamil/perf.test.js
passed in these millis: 21170
round 2:
$ node server.js
$ node /Users/alexamil/perf.test.js
passed in these millis: 4407
$ node /Users/alexamil/perf.test.js
passed in these millis: 4865
$ node /Users/alexamil/perf.test.js
passed in these millis: 4874
$ node /Users/alexamil/perf.test.js
passed in these millis: 20808
I am just curious what the explanation is for the server taking more time, even after finishing all requests. For example, I run perf.test.js, it finishes all requests. Then I manually run the same command again, about 1 or 2 seconds after the previous finished. Yet the response time still increases. We also see a big increase upon the fourth command.
The express server is like so:
'use strict';
import {ErrorRequestHandler} from "express";
import * as express from 'express';
import haven from 'domain-haven';
const app = express();
app.use(function (req, res, next) {
req.havenData = JSON.parse(req.query.haven || '{}');
next();
});
if (process.env.use_haven === 'yes') {
console.log('using haven');
app.use(haven());
}
app.use(function(req,res,next){
res.json({success: true});
});
app.use(function (err, req, res, next) {
err && console.error(err.message || err);
if (!res.headersSent) {
setTimeout(function () {
if (!res.headersSent) {
res.json({error: 'hit final error middleware', value: err && err.stack || err || null})
}
}, 10);
}
});
app.listen(6969, function () {
console.log('app is listening.');
});the test code is like so:
import http = require('http');
import async = require('async');
import request = require('request');
import {HavenData} from "./simple-server";
import assert = require('assert');
import util = require('util');
const tasks = Array.apply(null, Array(5000)).map(function () {
return function (cb: Function) {
const opts = {
json: true,
qs: {haven: null as any}
};
request.get('http://localhost:6969', opts, function (err, resp, v) {
if (err) {
return cb(err);
}
cb(null);
});
}
});
const now = Date.now();
async.parallelLimit(tasks, 15, function (err) {
if (err) throw err;
console.log('passed in these millis:', Date.now() - now);
});