Experiment with Casper.js

gistfile1.js

var clients = Array(10),
    url = 'http://localhost:5000/';

var on = function(resource) {
    if (resource.url.match('data.json'))
        this.echo("[update] Received: " + resource.url, 'INFO');
};

var start = function() {
    if (this.resourceExists('data.json')) {
        this.echo('Loaded data.json', 'INFO');
    } else {
        this.echo('Failed to load data.json', 'ERROR');
    }
};

var then = function() {
    this.echo("Loaded " + url, 'INFO_BAR');
};

for (var i = 0; i < clients.length; i++ ) {
    clients[i] = new require('casper').Casper({
        verbose: true,
        logLevel: "debug"
    });

    clients[i].on('resource.received', on);

    clients[i].start(url, start);

    clients[i].then(then);

    clients[i].wait(60000);

    clients[i].run();
}