How to Write Big Apps (Richard Rodger NodeDublin 2012)

HOW TO WRITE BIG APPS.Richard Rodger@rjrodger

Friday 26 October 2012

Node.js apps are getting bigger.


So, how do you scale?‣be stateless, ‣lots of little processes,‣funky V8 options,‣...


NO


How do you scale this?


Let's write a class for Cars.


Classicalfunction Car( params ) { this.color = params.color || "red" this.marque = params.marque || "Ferrari" this.model = params.model || "Testarossa" this.cylinders = params.cylinders || 12 this.timeto60 = params.timeto60 || 5.2 // seconds }

Car.prototype.drive = function() { console.log( "vrooom!" )}

var car = new Car({color:"yellow"})car.drive()


Classicalfunction Car( params ) { this.color = params.color || "red" this.marque = params.marque || "Ferrari" this.model = params.model || "Testarossa" this.cylinders = params.cylinders || 12 this.timeto60 = params.timeto60 || 5.2 // seconds }

Car.prototype.drive = function() { console.log( "vrooom!" )}

var car = new Car({color:"yellow"})car.drive()

VOTENOW


Prototypicalvar Car = { color: "red", marque: "Ferrari", model: "Testarossa", cylinders: 12, timeto60: 5.2, drive: function() { console.log( "vrooom!", this ) }}

var car = Object.create(Car)car.color = "yellow"car.drive()


Prototypicalvar Car = { color: "red", marque: "Ferrari", model: "Testarossa", cylinders: 12, timeto60: 5.2, drive: function() { console.log( "vrooom!", this ) }}

var car = Object.create(Car)car.color = "yellow"car.drive()

VOTENOW


Functionalfunction Car( params ) { var self = {}

var color = params.color || "red" var marque = params.marque || "Ferrari" var model = params.model || "Testarossa" var cylinders = params.cylinders || 12 var timeto60 = params.timeto60 || 5.2

self.drive = function() { console.log( "vrooom!", self ) } return self}var car = Car({color:"yellow"})car.drive()


Functionalfunction Car( params ) { var self = {}

var color = params.color || "red" var marque = params.marque || "Ferrari" var model = params.model || "Testarossa" var cylinders = params.cylinders || 12 var timeto60 = params.timeto60 || 5.2

self.drive = function() { console.log( "vrooom!", self ) } return self}var car = Car({color:"yellow"})car.drive()

VOTENOW


Which one should we use for Cars?


Let's play a GAME.


Stand up.


Stand up.Everybody.


Is this a car?


YES NOStay standing. Sit down.

And stay down!


Is this a car?


Is this a car?


Is this a car?


Is this a car?


Is this a car?


Is this a car?


Is this a car?It's a painting.


Which one?‣Classical‣Prototypical‣Functional


Which one?‣Classical‣Prototypical‣Functional

NONE!Friday 26 October 2012

‣Color - Lego?‣Marque - Batman brand?‣Model - Flintstones?‣Cylinders - Star Wars hover car?‣timeto60 - Model T max is 45mph

What's wrong with properties?


Classes are ideal Platonic forms.


‣Sides - 3!‣Points - 3!‣Total of Angles - 180°!

Think of the ideal triangle.


‣Sides - 3!‣Points - 3!‣Total of Angles - 180°!

Think of the ideal triangle.

Now picture it in your mind.


Plato was wrong.Ideal forms do not exist.


George Berkeley

berkeley.edusame guy

also Irish!Friday 26 October 2012

Inventor of...



There is no mental image of a ideal triangle.


Classes suck.Objects are ok.


Classes suck.Objects are ok.inherit

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Something is wrong with modeling a car.


But you can still drive all those cars.


It's not what you are.It's what you do.


‣Register a new user,‣Place an order,‣Call an external service,‣Save and load data,‣...

What does your app want to do?


This is JavaScriptJSON JSONfunction

A command for your app,

that "does stuff"

OUTPUT, asynchronously,

of courseINPUT(mostly in-

memory objects)


How do you find the right "thing to do"?


How do you find the right "thing to do"?PATTERN MATCHING!


{ thing: "product", cmd: "save",

... other fields}

{ thing: "product", cmd: "load",

... other fields}

doSave()

doLoad()


Define your "business logic" in terms of these commands.


What do you get as the pay off?


Really easy testing.Verify the returned JSON and you're done.


A distributed system, if you need it.That gives you scale too.


Completely decoupledcommands that never need to know about each other.


Plugins for free - just bundle up a few related commands.Organize your code!


middleware-style layering - e.g. add a caching layer by matching data storage commands.


Stay in control - tracing, logging, throttling, permissions, special cases - all easy.


Documentation - just list all the commands and the JSON they expect.


Code!Open sourced at http://senecajs.orgnpm install seneca


http://senecajs.org

http://senecajs.org

var seneca = require('seneca')()

// define a commandseneca.add({role:'math', cmd:'sum'}, function(args,callback) { var sum = args.left + args.right callback(null,{answer:sum}) })

// call the commandseneca.act({role:'math', cmd:'sum', left:1, right:2}, function(err,result) { if( err ) return console.error( err ) console.log(result) })

// prints: { answer: 3 }

Define and call a command.


// define a commandseneca.add({role:'math', cmd:'sum'}, function(args,callback) { var sum = args.left + args.right callback(null,{answer:sum}) })

// pin the APIvar math = seneca.pin({role:'math',cmd:'*'})

// call the commandmath.sum({left:1,right:2}, function(err,result) { console.log(result) })

// prints: { answer: 3 }

Pinning an API for convenience


seneca.use( function(seneca,options,callback) { seneca.add( {role:'math', cmd:'sum'}, function(args,callback) { var sum = args.left + args.right callback(null,{answer:sum}) })

seneca.add( {role:'math', cmd:'product'}, function(args,callback) { var product = args.left * args.right callback(null,{answer:product}) })

callback( null, seneca.http({ // just a connect middleware pin: {role:'math', cmd:'*'}, map: { sum: {}, product: {} }, // GET is the default HTTP method args: { left: parseFloat, right: parseFloat } }))})

var app = connect() .use(connect.query()) .use(seneca.service()) .listen(3000)// http://localhost:3000/api/sum?left=1&right=2

Plugins: commands + HTTP API.


// client: // use transport plugin to calculate product remotelyseneca.use('transport',{ pins:[ {role:'math', cmd:'product'} ]})

// this will go out over networkseneca.act({role:'math', cmd:'product', left:3, right:4}, function(err,result) { if( err ) return console.error( err ) console.log(result) })

// server (as per previous slide):seneca.use('transport')...app.use( connect.json() )...

Build a distributed system


var product = seneca.make('product')product.name = 'apple'product.price = 100

// ActiveRecord-styleproduct.save$(function( err, product ) { if( err ) return console.error( err ) console.log( 'saved: '+product )

// product.id was generated for you product.load$({id:product.id},function( err, product ) { if( err ) return console.error( err ) console.log( 'loaded: '+product ) })})

// output:// saved: //product:{id=286624;name=apple;price=100}// loaded: //product:{id=286624;name=apple;price=100}

// mix-and-match in-memory, MongoDB, MySQL, PostreSQL, etc.

Data storage (also plugin-based)


Also, seneca...‣is about 18 months old‣has detailed tracing‣has nice error messages‣has a REPL! @dshaw happy?‣is used in production


Why did we built it? builds Minimum Viable Products that become big apps.


senecajs.org@nodeseneca

Thanks!


Technology

How to Write Big Apps (Richard Rodger NodeDublin 2012)