Best way to read many files with nodejs?

The max listeners thing is purely a warning. setMaxListeners only controls when that message is printed to the console, nothing else. You can disable it or just ignore it.

The EMFILE is your OS enforcing a limit on the number of open files (file descriptors) your process can have at a single time. You could avoid this by increasing the limit with ulimit.

Because saturating the disk by running many thousands of concurrent filesystem operations won't get you any added performance—in fact, it will hurt, especially on traditional non-SSD drives—it is a good idea to only run a controlled number of operations at once.

I'd probably use an async queue, which allows you to push the name of every file to the queue in one loop, and then only runs n operations at once. When an operation finishes, the next one in the queue starts.

For example:

var q = async.queue(function (file, cb) {
    var stream = fs.createReadStream(file.path);
    // ...
    stream.on('end', function() {
        // finish up, then
        cb();
    });
}, 2);

globStream.on('data', function(file) {
    q.push(file);
});

globStream.on('end', function() {
    // We don't want to add the `drain` handler until *after* the globstream
    // finishes.  Otherwise, we could end up in a situation where the globber
    // is still running but all pending file read operations have finished.
    q.drain = function() {
        // All done with everything.
    };

    // ...and if the queue is empty when the globber finishes, make sure the done
    // callback gets called.
    if (q.idle()) q.drain();
});

You may have to experiment a little to find the right concurrency number for your application.