Pooled connections - monitoring concurrent requests in Node.js Request library?

Question

I'm sending out a lot of requests to another server, and want to limit them so as to not overload the server. My impression is that this can be done with the pool parameter in options, but I'm not sure if I'm doing so properly.

I'd like to be able to keep track of when the requests are sent out, as I'm trying to establish a duplex connection, and need to make sure the corresponding GET and POST requests are sent out at the same time.

Here's a simplified example of what I'm trying:

var request = require('request');

var options = {
    'url': 'http://www.google.com',
    'pool': {
        'maxSockets': 3
    }   
};
for (var i = 0; i < 100; i++) {
    request.get(options, (function(j) {
        return function(err, res, body) {
            console.log(j);
        }
    })(i)); 
}

Is there an event emitted when the requests are actually sent out? Is there any way for me to track when, and in what order each request is being sent out?

Answer 1

I found this in the Node.js documentation:

Event: 'socket'#

function (socket) { }

Emitted after a socket is assigned to this request.

You can use it to monitor connections as they are assigned sockets like this:

http.get(options, function(res) {
    // Do stuff
}).on("socket", function (socket) {
    socket.on("connection") {
        // record connection
    };
});

The same event is emitted with the request library, since it's just a wrapper around the builtin http module.