Memory leaks in node.js with concurrent sse connections

Question

Memory leaks in node.js with concurrent sse connections

i'm developing high-load testing tool, using eventsource npm library to generate concurrent sse connections.

I use CentOS on digitalocean with 512Mb and 1CPU.

Take a look at my code:

var http = require("http"), 
EventSource = require('eventsource'),
openSockets = 0;
http.globalAgent.maxSockets = 70000;

console.log(process.memoryUsage() )

beginTest();

function beginTest (options) {
  for (var i = 0; i < 50000; i++) {
    setTimeout(formPoster(i),0);
  }
}
function formPoster (i) {
  var url = "http://remoteserver.com/examples/events/connect.sse",
      es = new EventSource(url);

  es.onmessage = function(e) {

  }; 
  es.onerror = function(e) {
    console.log(e);
  };
  es.onopen = function(e) {
    openSockets++;

    if (openSockets == 1 ) {
      console.log(process.memoryUsage() );
      process.exit(code=0);  

    }

};
}

The problem with that code is huge memory leak - first console.log statement outputs

{ rss: 8925184, heapTotal: 5066496, heapUsed: 2113192 }

whereas the second one (after first connected ) outputs { rss: 373219328, heapTotal: 296538752, heapUsed: 286450700 } herewith remoteserver has around 1500 connection with local machine.

What reasons can cause such memory leaks?

javascript
node.js

Answer 1

You don't have a memory leak - you are simply instantiating a lot of objects at the same time and a garbage collection event has probably not yet occurred.

The line setTimeout(formPoster(i),0) isn't doing what you think - because you're formPoster, rather than passing a reference, the timeout has no effect. You are simply calling formPoster 50,000 times immediately.

In fact, even if you did pass a function to setTimeout for deferred execution like this:

setTimeout(function() {
  formPoster(i)
})

Then you would still see the same effect, just deferred to a later execution of the event loop.