gistfile1.js

// This is a design doc for adding two methods to node via monkey patching
// that I find useful in all the little bits of HTTP glue I make. The point
// is to create a useful abstraction for forwarding requests and linking
// responses. In the most trivial case for building a reverse proxy, but
// see below for other use cases.

// API
http.ServerRequest.prototype.forward(port, host, dataFilter=null)
http.ServerResponse.prototype.attach(requestOrResponse, responseFilter=null, dataFilter=null)

// Simple reverse proxy
var server = http.createServer(function(req, resp)) { 
    resp.attach(req.forward(8080, 'localhost')); 
});
server.listen(80);

// Simple SSL frontend
var server = http.createServer(function(req, resp)) { 
    req.headers['X-Forwarded-Proto']    = 'https';
    req.headers['X-Forwarded-For']      = req.connection.remoteAddress;
    resp.attach(req.forward(80, 'localhost')); 
});
server.setSecure(crypto.createCredentials({key: 'key', cert: 'cert'}));
server.listen(843);

// Simple load balancer
var hosts   = ['hostA', 'hostB', 'hostC'];
var cursor  = 0;
var server = http.createServer(function(req, resp)) { 
    resp.attach(req.forward(80, hosts[cursor])); 
    cursor += 1;
    if (cursor == hosts.length) cursor = 0;
});
server.listen(80);

// Fire and forget request fanout
var hosts   = ['hostA', 'hostB', 'hostC'];
var server = http.createServer(function(req, resp)) { 
    for (var host in hosts) {
        req.forward(80, host);
    }
    resp.writeHead(201);
    resp.end();
});
server.listen(80);

// Webhook gate 
// (only proxy if hook request succeeds, else return hook response)
var webhook = url.parse("http://example.com/continue-or-cancel-script");
var server = http.createServer(function(req, resp)) { 
    var hookRequest = http.createClient(webhook.port, webhook.host)
            .request(webhook.pathname);
    hookRequest.addListener('response', function(hookResponse) { 
        if (hookResponse.statusCode == 200) {
            resp.attach(req.forward(8080, 'localhost'));
        } else {
            resp.attach(hookResponse);
        }
    }
});
server.listen(80);

// Simple page caching
var cache = {};
var server = http.createServer(function(req, resp)) { 
    if (req.method == 'GET') {
        if (cache.hasOwnProperty(req.url)) {
            resp.writeHead(200);
            resp.write(cache[req.url]);
            resp.end();
        } else {
            resp.attach(req.forward(8080, 'localhost'), null, function(data) {
                cache[req.url] += data; 
                return data;
            });
        }
    } else {
        resp.attach(req.forward(8080, 'localhost')); 
    }
});
server.listen(80);