Postpone responding to request in Node.js - node.js

Question

When my Node.js Express server, which is listening on port 3000, receives a request, it routes to a function that must issue a POST to another Web site and get the response before responding to the initial request.
Is that possible?
Here is the code I'm using:
app.get('/silence/:host', routes.silence);
http.createServer(app).listen(app.get('port'), function(){
console.log('Express server listening on port ' + app.get('port'));
});
exports.silence = function(request, response){
var hostname = utils.validateHost(request);
if (stash.createSilencer(hostname)) {
response.writeHead(200, {"Content-Type": "application/json"});
response.write('{ "success" : true, "message" : "Successfully silenced host'" }');
response.end();
}
}
exports.createSilencer = function(hostname) {
var options = {
url: 'http://x.x.com:4567/create/silencer/' + hostname ,
method: 'POST',
body: '{ "timestamp": ' + utils.timestamp() + '} '
};
request(options, silencer_callback);
##### DONT WANT TO RETURN UNTIL THE silencer_callback IS INVOKED
return true;
}
function silencer_callback(error, response, body) {
if (!error && response.statusCode == 200) {
var info = JSON.parse(body);
console.log("Response Recieved");
}
}

Answer 1

The trick is that you don't call response.write() and response.end() until you receive a response from you POST request. You just exit the method without sending response back. Once you have result from your POST request, you can finish initial response.
exports.silence = function(req, res){
var hostname = utils.validateHost(req);
stash.createSilencer(hostname, function(error, response, body) {
if (!error && response.statusCode == 200) {
var info = JSON.parse(body);
console.log("Response Received");
}
// we get POST-response, lets response to initial request here
res.writeHead(200, {"Content-Type": "application/json"});
res.write('{ "success" : !error, "message" : "Successfully silenced host'" }');
res.end();
});
// return from the function, but do not send response back yet
}
exports.createSilencer = function(hostname, callback) {
var options = {
url: 'http://x.x.com:4567/create/silencer/' + hostname ,
method: 'POST',
body: '{ "timestamp": ' + utils.timestamp() + '} '
};
request(options, callback);
// return from the function, but do not send response back yet
}