how to use setTimeout asynchronously in node.js

Question

I'm new to node.js, I tried to use setTimeout to simulate long connections and hope it act asynchronously.

var http = require('http');

http.createServer(function (request, response) {
    console.log('New request @ ' + request.url);
    (function (response) {
         setTimeout(function () {
             console.log('Time is up');
             response.writeHead(200, {"Content-Type": "text/plain"});
             response.end('Hello World\n');
         }, 3000);
     })(response);
}).listen(8124);

console.log('Server running at http://127.0.0.1:8124/');

But, the code above perform like a synchronous single thread app, which can only handle one request per 3 seconds.

I thought everything in node.js should act asynchronously. So, what's the problem here?

balazs · Accepted Answer · 2012-12-20 11:54:24Z

8

The SetTimeout is async, you don't need that anonym function in the middle, just write this.

var http = require('http');

http.createServer(function (request, response) {
  console.log('New request @ ' + request.url);
  setTimeout(function () {
    console.log('Time is up');
    response.writeHead(200, {"Content-Type": "text/plain"});
    response.end('Hello World\n');
  }, 3000);
}).listen(8124);

console.log('Server running at http://127.0.0.1:8124/');

If you produce 10 concurent request the total comp time will be around 3sec, which means it is async. You can use the ab tool to check, or if you program node, maybe easier to install http-perf. and run nperf -c 10 -n 10 http://127.0.0.1:8124

answered Dec 20, 2012 at 11:54

balazs

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3 Comments

Jack Over a year ago

I've tested with ab, and you're right, setTimeout is an async function. But, it's a bit strange if I open several tabs in Chrome at the same time, it ends one by one between a 5 seconds interval.

balazs Over a year ago

I think you just not enough fast clicking between the tabs in chrome.. :)

Jason Over a year ago

Chrome will not request the same URL concurrently. If you add a variation to the url, e.g. the first tab requests 127.0.0.1:8124/0, the second requests 127.0.0.1:8124/1, etc, then they should behave like you expect. See stackoverflow.com/questions/15852011/…

Marcus Granström · Accepted Answer · 2012-12-20 11:37:42Z

0

You need to run your sleep in a new process. There is a module that can help you (https://github.com/cramforce/node-worker) or you can look at the normal api documentaion about spawn.

answered Dec 20, 2012 at 11:37

Marcus Granström

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Comments

user3238692 · Accepted Answer · 2014-01-26 23:18:49Z

-3

var async,
__slice = [].slice;

async = require("async");

async.setTimeOut = function() {
    var arg, args, callback, delay, runWithTimeOut;
    callback = arguments[0], delay = arguments[1], arg = arguments[2], args = 4 <= arguments.length ? __slice.call(arguments, 3) : [];
    runWithTimeOut = function() {
        return setTimeout(callback, delay, arg, args);
    };

return async.parallel([runWithTimeOut]);
};

answered Jan 26, 2014 at 23:18

user3238692

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