demo.js

var B = require("bluebird");
var _ = require("lodash");


function run(concurrency) {
    function log(id, msg) {
        // only logging first 100
        if(id <= 100) {
            console.log(id + " -> " + msg);
        }
    }

    function waitFor(id ,duration, remaining) {
        if(_.isUndefined(remaining)) { remaining = duration; }

        if(remaining <= 0) {
            log(id, "done");
            return;
        }

        log(id, remaining + "/" + duration + " seconds remaining");
        return B.delay(1000)
            .then(function(){
                return waitFor(id, duration, remaining - 1);
            });
    }

    var promises = [];
    _.times(concurrency, function(idx) {
        promises.push(B.delay(Math.random()*1000) // spreading the load
            .then(function() {
                return waitFor(idx + 1, 10);
            }));
    });
    ids = null;

    B.all(promises).then(function() {
        console.log("All done");
    }).done();
}

//run(10);
//run(100);
//run(1000);
//run(10000);
//run(100000);
run(500000);
//run(1000000); // reaching the limit, too much gc
//run(1500000); // about the the limit
//run(2000000); // crashes