Nodejs Explained with Examples

this presentation code is on
https://github.com/gabrielelana/node-examples

gabriele lana
gabriele.lana@cleancode.it
twitter: @gabrielelana
this presentation code is on
https://github.com/gabrielelana/node-examples

why
node.js?

“Node's goal is to
provide an easy
way to build
scalable network
programs”

http://nodejs.org/#about

what is
node.js?
• asynchronous i/o framework
• core in c++ on top of v8
• rest of it in javascript
• swiss army knife for network
related stuffs
• can handle thousands of
concurrent connections with
minimal overhead (cpu/memory)
on a single process

multiple thread
synchronous I/0

you can
“always”
scale with
multiple
machines but
it costs
you $$$

Nodejs Explained with Examples

CPU BOUND
TASKS?

but...
what is HE
doing?

CPU BOUND
TASKS?

...OR I/o
but... BOUND
what is HE TASKS?
doing?

synchronous I/0

function productsInCart(request, response) {
    var db = new Db()
    var user = new User(request)
    if (user.isAuthorized("cart/products")) {
        response.write(
            JSON.stringify(
                db.productsInCart(user.cartId())
            )
        )
    } else {
        response.unauthorized()
    }
}

single thread
asynchronous I/0

single source events
STATES

EVENTS
http://www.infoq.com/presentations/Death-by-Accidental-Complexity

single source events
    var db = null, user = null, ...
    createDb()
    handle(function(source, event) {
        if (event["name"] === "createDb") {
            if (db === null) {
                db = event.data
                createUser(request)
            } else {
                ????
            }
        } else if (event["name"] === "createUser") {
            if (user === null) {
                user = event.data
                ...
            } else {
                ???
            }
        ... 
        } else {
            source.push(event, state)
        }
    }, "_initial")
}

asynchronous I/0
single thread
asynchronous I/0

I am
“callback”
call me
if you
need me...

asynchronous I/0
single thread
asynchronous I/0

multiple source events
(local state)
STATES

EVENTS

multiple source events
(local state)
    createDb(function(db) {
        createUser(function(user) {
            if (user.isAuthorized("cart/products") {
                response.write(
                    JSON.stringify(
                        db.productsInCart(user.cartId())
                    )
                )
                response.end()
            }) else {
                response.unauthorized()
            }
        })
    })
}

Event Emitter
(local state)
var http = require("http")

var server = http.createServer(function(request, response) {
  response.writeHead(200, {
    "Content-Type": "plain/text"
  })
  response.write("Hello Worldn")
  response.end()
})

server.listen(8080)

console.log("> SERVER STARTED")

01#hello_world/hello_world_server.js

Event Emitter
(local state)
coder@apollo:~/Work/src/node/examples$ node hello_world_server.js
> SERVER STARTED
#1
coder@apollo:~$ curl "http://localhost:8080/"
Hello World
#2

Event Emitter
(local state)
var server = require("http").createServer()

server.on("request", function(request, response) {
  console.log("> REQUEST STARTED")
  request.on("end", function() {
    console.log("> REQUEST CLOSED")
    response.writeHead(200, {
      "Content-Type": "plain/text"
    })
    response.end("Hello Worldn")
    server.close()
  })
  response.on("close", function() {
    console.log("> RESPONSE CLOSED")
  })
})

01#hello_world/hello_world_server_emitter.js

Event Emitter
(local state)

...

server.on("close", function() {
  console.log("> SERVER CLOSED")
})

server.on("listening", function() {
  console.log("> SERVER STARTED")
})

server.listen(8080)

01#hello_world/hello_world_server_emitter.js

Event Emitter
(local state)
coder@apollo:~/Work/src/node/examples$ node hello_world_server.js
> SERVER STARTED #1
coder@apollo:~$ curl "http://localhost:8080/"
Hello World #2
#1
> REQUEST STARTED
> REQUEST CLOSED
> SERVER CLOSED

data streams
  var chunks = [],
      output = fs.createWriteStream("./output")

  request.on("data", function(chunk) {
    chunks = forEachLine(chunks.concat(chunk), function(line) {
      output.write(parseInt(line, 10) * 2)
      output.write("n")
    })
  })

  request.on("end", function() {
    response.writeHead(200, { "Content-Type": "plain/text" })
    response.end("OKn")
    output.end()
    server.close()
  })
})
02#proxy_stream/proxy_stream.js

Event Emitter
(local state)
coder@apollo:~/Work/src/node/examples$ node stream_doubler.js
#1
coder@apollo:~$ curl "http://localhost:8080/" --data $'1n2n3n'
OK #2
coder@apollo:~/Work/src/node/examples$ cat output
2
4
6 #1

why
javascript?

• Friendly callbacks
• ubiquitous (well known)
• no I/o primitives
• one language to rule them all

web applications
before: a web
mind shift #1 server with some
application logic

application
Web server
application

application

application

web applications
after: an application
mind shift #1 accessible over
http

web server

application

web applications
after: an application
mind shift #1 that can
communicate and
collaborate with
web server
the world

application

web applications
before: stateful
mind shift #2 • no easy to scale
• no easy to reuse

v
M
c

web applications
before: stateful

v
M
c

conversation application
state state

web applications
before: stateful

v
M
c

tightly coupled

web applications
after: stateless
mind shift #2 • easy to scale
• easy to reuse

v
http
M
c

web applications
after: stateless
mind shift #2 • easy to scale
• easy to reuse

v
http
M
c

conversation application
state state

web applications
after: stateless
mind shift #2
http

web server
M
http

statefull
connection

• easy to scale M
• easy to reuse

INSTALL NPM
(node packet manager)

coder@apollo:~/Work/src/node/examples$ curl http://npmjs.org/install.sh | sh
...
npm ok
It worked

coder@apollo:~/Work/src/node/examples$ npm list | wc -l
1776

coder@apollo:~/Work/src/node/examples$ npm install connect@0.2.5
coder@apollo:~/Work/src/node/examples$ npm install faye@0.5.3
coder@apollo:~/Work/src/node/examples$ npm install backbone@0.3.0
coder@apollo:~/Work/src/node/examples$ npm install underscore@1.1.2

static handler

var server = connect.createServer(connect.logger({ "buffer": true }))
  .use("/", connect.router(function(resource) {
    resource.get("/board", function(request, response, next) {
      request.url = "/board.html"
      next()
    })
    ...
  }), connect.staticProvider({ 
    "root": path.join(__dirname, "static"), 
    "cache": true 
  }))

server.listen(port)

05#tictactoe/server.js

game handler
(generate board-id)

    resource.post("/board", function(request, response) {
      response.writeHead(200, { "Content-Type": "application/json" })
      uuid(function(boardId) {
        response.end(
          JSON.stringify({
            "board": { "id": boardId }
          })
        )
      })
    })


game handler
(initial board/user)
    resource.get("/board/:id", function(request, response) {
      var board = boards.get(request.params["id"])
      if (board === undefined) {
        board = new Board({ "id": request.params["id"] })
        boards.add(board)
      }
      uuid(function(userId) {
        var user = board.user(userId)
        response.writeHead(200, { "Content-Type": "application/json" })
        response.end(
          JSON.stringify({
            "board": board,
            "user": user
          })
        )
      })
    })

game handler
(make your move)

    resource.post("/board/:id", function(request, response) {
      waitForBody(request, function(body) {
        boards.get(request.params["id"]).move(JSON.parse(body))
        response.writeHead(204, { "Content-Type": "application/json" })
        response.end(JSON.stringify({ "response": "ok" }))
      })
    })


comet handler

var comet = new Faye.NodeAdapter({ "mount": "/comet", "timeout": 50 })

var server = connect.createServer(connect.logger({ "buffer": true }))
  .use("/comet", function(request, response, next) {
    comet.handle(request, response)
  })
  ...
})

comet.attach(server)


comet EVENTS
on backbone events

var client = comet.getClient()
var boards = new Backbone.Collection

boards.bind("change", function(board) {
  client.publish("/board-" + board.get("id"), board)
})


in browser
routing

$(function() {

  $.sammy(function() {
    
    this.get("", function(context) {
      $.post("/board", function(response) {
        context.redirect("#/board/" + response["board"]["id"])
      })
    })

    ...
  }).run()
})

05#tictactoe/static/board.html

in browser
routing/start game

    var comet = new Faye.Client("/comet")
    var game = new Game()

    this.get("#/board/:id", function(context) {
      game.start()
      $.get("/board/" + context.params["id"], function(response) {
        game.set({ "me": new User(response.user) })
        game.set({ "board": new Board(response.board) })
        comet.connect()
        comet.subscribe("/board-" + context.params["id"], function(board) {
          game.get("board").set(board)
        })
      })
    })

05#tictactoe/static/board.html

in browser
game logic example

  window.Game = Backbone.Model.extend({
    "initialize": function() {
      ...
      game.get("board").bind("change", function() {
        if (this.isMyTurn()) {
          return game.trigger("make-your-move")
        }
        return game.trigger("wait-for-move")
      })
    }
  })

05#tictactoe/static/js/application.js

in browser
game logic example
    game.bind("play-with-board", function(cells) {
      buildBoard(['_'].concat(cells))
    })

    game.bind("play-with-mark", function(mark) {
      showPlayerMarker(cellMarksUrl[myMark = mark])
    })
    game.bind("make-your-move", function() {
      $("#board").undelegate()
      $("#board").delegate("*[id^=cell]", "mouseover", function() {
        $(this).data("cell").select()
      })
      $("#board").delegate("*[id^=cell]", "mouseout", function() {
        $(this).data("cell").unselect()
      })
      ...

05#tictactoe/static/js/application.js

the fork
be with you

#!/bin/bash

for count in `seq 1 100`; do
    echo $count
    sleep 0.1
done

03#long_running_jobs/long_running_job.sh

the fork
be with you
var spawn = require("child_process").spawn,
    server = require("http").createServer()

  var job = spawn("./long_running_job.sh")

  job.stdout.on("data", function(tick) {
    response.write(tick)  
  })

  job.on("exit", function() {
    response.end()
  })
})

03#long_running_jobs/long_running_server.js

the fork
be with you
coder@apollo:~$ ab -c 1 -n 1 "http://localhost:8080/"
...
Concurrency Level: 1
Time taken for tests: 10.531 seconds
...

...
...

the fork
be with you
...
...

...
...

...
...

enter comet

w
at
at ch
watch
ch
M spawn
w

watch
w

w
t a

at
ch

ch

static handler

var port = 8080

var server = connect.createServer(connect.logger())
  .use("/comet", function(request, response) { ... })
  .use("/spawn", function(request, response) { ... })
  .use("/", connect.staticProvider({ 
    "root": path.join(__dirname, "static"), 
    "cache": true 
  }))

comet.attach(server)

server.listen(port)

04#progress/progress_server.js

comet handler

var comet = new Faye.NodeAdapter({
  "mount": "/comet", "timeout": 50 
})

  .use("/comet", function(request, response, next) {
    comet.handle(request, response)
  })
  ...


spawn handler
var client = comet.getClient(), jobCounter = 0

  .use("/comet", function(request, response) { ... })
  .use("/spawn", function(request, response, next) {
    var worker = spawn("./long_running_process.sh"),
        jobId = jobsCounter++
        
    response.writeHead(200, { "Content-Type": "plain/text" })
    response.end("OKn")

    worker.stdout.on("data", function(progress) {
      client.publish("/job-progress", { 
        "id": jobId, 
        "progress": parseInt(progress.toString(), 10)
      })
    })
  })

in browser

<script>
  $(function() {
    var comet = new Faye.Client("/comet")

    comet.connect()
    comet.subscribe("/job-progress", function(job) {
      $("#template").progressBar(job.id, job.progress)
    })
  })
</script>

04#progress/static/index.html

node.js is
awesome
but when
should i
use it?

when to use it?

• chat/messaging
• real-time applications
• intelligent proxies
• high concurrency applications
• communication hubs
• coordinators

please tell
me something
bad about
node.js

some warnings

• release stable 0.2.4 (young)
• lots of stuffs to look at
• lots of half backed stuffs
• retro compatibility???
• bad at handling static contents
• hard to find organized and
authoritative informations

Nodejs Explained with Examples

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