When to use Node? Lessons learned

When to use Node.js?
Lessons learned
Coen Stevens - Amsterdam Node Meetup 2012

@beatlevic BeatleTech.com

Saturday, March 31, 12

Why not Node.js
• We never heard of Node.js at the time (2009)
and were experienced in Ruby
• Lots of server-side computations / statistics /
map-reduce (blocking the node event-loop)
• Typical dashboard (view on a database)
• Not that many concurrent users
• No need for open connections
Yes, I would use Ruby again

Pivot: Penny auctions

• Swoopo and Bigdeal (real goods)
• Newcope a platform for pay-per-bid
auction games for virtual goods


Flash game platform

http://newcope-heyzap.heroku.com/home

• The Broth: BarnBuddy
• Facebook app
• Similar to Farmville
• Over 1 million active users per month


Challenge

• Build iframe / facebook app solution
• Have the auctions as realtime as possible
• Long polling (later websockets) vs pulling
• Lots of users with open connections
• Scalable


Languages considered

• Ruby (Eventmachine, no Goliath yet)
• JRuby
• Scala (Twitter had just moved from ruby)
• Erlang
• Javascript Node.js


Node.js experiences
• Functional programming

• Javascript for both client and server

• Very good performance (30k users the ﬁrst day)

• Node v0.1.25 and no packet manager (npm)

• MySQL with DBSlayer (later Mongodb)

• Nginx to serve static ﬁles

• Easy to setup/deploy on EC2 (upstart deamon)

• Everything async (annoying to test)

• Fun!
Yes, I would use Node.js again

Auction.prototype.startTimer = function() {
var self = this;
if (this.timer) clearTimeout(this.timer);
  this.emit("start");
  this.timer = setTimeout(function() {
    self.emit("end");
  }, self.timeLeft() * 1000);
}

Auction.prototype.bid = function(user) {
    var self = this;
    return function (callback, errback) {
     if (user.bid_count > 0 && self.status() === "running") {
        user.bid_count -= 1;
        dbUser.updateUser(user.id, {'bid_count': user.bid_count})(function(result){
          if (self.timeLeft() < self.bidTimeDelta) {
            self.setTime(me.bidTimeDelta);
          };
          self.price += self.bidPriceDelta;
          var bid = { user: user, ts: new Date() }
          self.bids.push(bid);
          self.bidCount++;
          callback(self);
        }, function(error) {
          user.bid_count += 1;
          errback("Could not update new bid count");
        })
     } else {
        errback("Bid could not be placed");
     }
  };
}


// continuation style
var bid = function(user) {
return function (callback, errback) {
if (!user) return errback("No user")
callback(user)
}
}

bid(user)(function(result){
console.log(result)
}, function(error) {
console.log(error)
})


// promise style
var bid = function(user) {
var promise = new Promise()
if (!user) {
promise.emitError("No user")
} else {
promise.emitSuccess(user)
}
return promise
}

var promise = bid(user)
promise.addErrback(function(error){
console.log(error)
})
promise.addCallback(function(result) {
console.log(result)
})


• // callback style
var bid = function(user, callback) {
if (!user) return callback("No user")
callback(null, user);
}

bid(user, function(err, result){
if (err) console.log(err)
console.log(result)
})


• Bottlenose is the smartest social media
dashboard.
• Helping you manage the information overload
on streams like twitter and Facebook
• Bottlenose analyzes and ﬁlters messages using
NLP and clustering techniques
• Beta launched December 2011
http://bottlenose.com

Why Node.js?
• It began (2009) with NLP in javascript, run
it both on the client and the server
• Fat client and lean server
• Realtime stream updates
• Lots of users (with open connections)
• Alternatives?
Yes, I would use Node.js again

Summary:
When to use Node?
• When you are building more of an app than a
website and require lots of open connections to
the server
• When you want your users to get data in
realtime (chat, streams)
• When you have to serve lots of requests that do
not take too many cpu cycles (blocking the loop)
• When you like to work with Javascript all the way

Thanks!

@beatlevic

When to use Node? Lessons learned

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