Sustainable Agile Development

federico.galassi@gmail.com

gabriele.lana@gmail.com

a case study with chess

We havean Idea

We want tomake it work

We know thatAgile works in acorporate world

Can Agile workfor us/you too?

Eric Ries: “a startup is a human institution designed to deliver a new product or

service under conditions of extreme uncertainty”

Traditional Product Development(Progress: Advance To Next Stage)

Eric Ries @ http://startuplessonslearned.blogspot.com/

Requirements

Design

Implementation

Verification

Manteinance

Problem: Known

Solution: Known

Agile Development(Progress: Running Tested Features)

Eric Ries @ http://startuplessonslearned.blogspot.com/

Problem: Known

Solution: Unknown

"Product Owner" or

in-house customer

we should be able toEmbrace Change

Cos

t of

Chan

ge Traditional Development

Agile Development

Time

we should be able toEmbrace Change

• Refactoring• Simple Design• Test-Driven Development• Continuous Integration• Collective Code Ownership• Incremental Design• Emergent Design• Pair Programming• Project Automation• Definition of Done• Exploratory Testing

We know how to do it, But...

Do you really know what

customers want?

Do you really think customers know what they

need?

Do you thinkimplementing

features isreal progress?

7%

13%

16%

19%

45%

Use of Requested Features

Standish Group, CHAOS Report 2006

The biggest source of waste isimplementation of features nobody wants

They could even

hate some “features”

Steve Blank:“software

development is a discovery and a

learning process”

Lean Startup Development(Progress: Validated Learning about Customers)

Eric Ries @ http://startuplessonslearned.blogspot.com/

Problem: Unknown

Solution: UnknownCustomer Development

Agile in a Waterfall world

ConceptAgile

Development

Test

Alpha/Beta

Maintenance

and Marketing

Debug, Fix

and Patch

Agile in a Waterfall world

ConceptAgile

Development

Test

Alpha/Beta

Maintenance

and Marketing

Debug, Fix

and Patch

Agile in a Waterfall world

ConceptAgile

Development

Test

Alpha/Beta

Maintenance

and Marketing

Debug, Fix

and Patch

Lean Startup Development(Progress: Validated Learning about Customers)

Eric Ries @ http://startuplessonslearned.blogspot.com/

IDEAS

CODEDATA

BUILD

MEASURE

LEARN

• Reduce the cycle time

• Eliminate waste• Optimize the

whole• Amplify learning

MinimumMarketable

Feature

How can we support the

learning process?

Domain Composability: the Domain Model

should beextremely flexibleand “exposed”

web applicationsInformation Flow

HTTPOOP

RDB

MS

Impedance Mismatchcan slow you down

HTTPOOP

RDB

MS

Accidental Complexity

Resource Oriented Architectures

HTTP ROA DATA

Essential Complexity

Identify Resourcesin your Domain

Resource Oriented Architectures

Resource Oriented Architectures

BoardGame

Position

Move

FileRankPlayer

Square

Knight

Queen

Rook

Pawn Bishop

Resource Oriented Architectures

Design the URIs (Ubiquitous Language)

Resource Oriented Architectures

GET /position/wqd3,wkd2,bke8 HTTP/1.1Accept: text/plain

HTTP/1.1 200 OKContent-Type: text/plain;format=fen\n5k2/8/8/8/8/3Q4/8/3K4

Resource Oriented Architectures

GET /position/wqd3,wkd2,bke8 HTTP/1.1Accept: image/png;q=0.8, text/plain;q=0.2

HTTP/1.1 200 OKContent-Type: image/png\nPNG...

Resource Oriented Architectures

GET /board/4815162342 HTTP/1.1

HTTP/1.1 200 OK\n.../position/wqd3,wkd1,bke7/position/wqd3,wkd1,bke8

Resource Oriented Architectures

HTTP/1.1 201 Created\n.../position/wqd3,wkd1,bke8/position/wqe8,wkd1,bke8

POST /board/4815162342 HTTP/1.1\nmove = d3-e8

Resource Oriented Architectures

HTTP/1.1 200 OK\nboard = /board/4815162342white = /player/50298black = /player/48192

GET /game/42 HTTP/1.1

no Web Servicesbut how the web

should be

Resource Oriented Architectures

Resource Oriented Architectures

Tim Berners-Leeon Linked Data

“... almost 20 years ago I wanted to reframe the way we use informations ... I invented the Word Wide Web ... now is time for a new reframing...”

Tim Berners-Lee @ http://linkeddata.org

Resource Oriented Architectures

for each Resourcedesign the

Representationsfrom and to the Client

Resource Oriented Architectures

GET /game/42 HTTP/1.1Accept: application/xhtml+xml

<html> ... <a rel=”owner” href=”/player/1001”>...</a> ... <ul class=”moves”> <li><image src=”/position/initial.png”/></li> </ul></html>

now we have aGood Domain

but anUgly Interface

Ajax to rescue

// Interface can have its state// but actually consumes many serverside// resources in background

var game = { "game": "/game/42", "board": "/board/4815162342", "position": "/position/” + “rnbqkbnr-pppp1ppp-8-4p3-4P3-8-PPPP1PPP-RNBQKBNR"}

var req = YAHOO.util.Connect.asyncRequest;

req('GET', position + '/piece/g1/moves', callback);// 200 OK; moves = g1-e2, g1-f3, g1-h3board.highlightSquares("g1", "e2", "f3", "h3");

req('POST', '/board/4815162342', callback, "move=g1-f3");// 200 OK; position = // rnbqkbnr-pppp1ppp-8-4p3-4P3-5N2-PPPP1PPP-RNBQKB1R

John Maeda’sLaws of Simplicity

Law 3: TIMESavings in time feels like simplicity.

John Maeda @ http://lawsofsimplicity.com

...ok, we need real-time

Comet to rescue

• “Reverse Ajax”• Push over Pull• Long-lived HTTP

But which Comet way?

Long pollingForever FrameScript tagsWebSocketsHtmlfileMime MessagingFlash Remoting

Transport APISocketPublish/SubscribeAPI basedData syncREST?

Joe Walker @ http://www.slideshare.net/joewalker/comet-and-the-rise-of-highly-interactive-websites-presentation

HTTP Channelsis RESTful Comet

“The primary purpose of HTTP Channels is to provide an application-level Comet

protocol for live data synchronization that leverages the widely understood semantics

and vocabulary of HTTP/REST.”

Kris Zyp:

Kris Zyp @ http://cometdaily.com/2008/06/05/intended-usage-of-http-channels/

Http Channels 2

Kris Zyp @ http://cometdaily.com/2008/05/13/http-channels-2/

POST /channels HTTP/1.1Accept: application/httpX-Create-Client-Id: 123123

GET /foo HTTP/1.1Accept: */*X-Subscribe: *X-Client-Id: 123123

PUT /foo HTTP/1.1\n{ data: “foobar” }

HTTP/1.1 200 OKX-Event: PUTContent-Location: /foo \n{ data: "foobar" }

Http Channels 3

X-Client-Id: 124124 X-Client-Id: 126126X-Client-Id: 125125

X-Client-Id: 123123

HTTP/1.1 200 OKX-Event: POSTContent-Location: /board/4815162342 \nmove = g1-f3

POST /board/4815162342 HTTP/1.1\nmove = g1-f3

How can wespeed up the

learning process?

Continuous Deployment reduces the time from

code check-in to production

Testabilitytells if it’s a good

change or a bad change as quickly as possible

Continuous Deployment

Continuous Deployment (testability)

HTTP

View Model

Control

Continuous Deployment (testability)too much code untested

HTTP

View Model

Control

HTTP

View Model

Control

Continuous Deployment (testability)too fragile and unreliable

Continuous Deployment (testability)Ruby with Rspec and Cucumber

HTTP

Board

Game

Player

Position

Move

Js

Continuous Deployment (testability)

Feature: change the position on board

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd8,wkd1,bke8 Then response should be 201 And board should be in position wqd8,wkd1,bke8

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd7,wkd1,bke8 Then response should be 403 And board should be in position wqd3,wkd1,bke8

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd8,wkd1,bke8 Then response should be 201 And board should be in position wqd8,wkd1,bke8

Continuous Deployment (testability)

Given /^board with position (.+?)$/ do | from_position | response = @client.post("/board", "position = #{from_position}") response.status.should == 201 @board = response.header["Location"]end

Continuous Deployment (testability)

When /^move to position (.+?)$/ do | to_position | move_reponse = @client.post(@board, "position = #{to_position}") @move_response_status = move_response.statusend

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd8,wkd1,bke8 Then response should be 201 And board should be in position wqd8,wkd1,bke8

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd8,wkd1,bke8 Then response should be 201 And board should be in position wqd8,wkd1,bke8

Continuous Deployment (testability)

Then /^response should be (\d{3})$/ do | expected_response_status | @move_response_status.should == expected_response_statusend

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd8,wkd1,bke8 Then response should be 201 And board should be in position wqd8,wkd1,bke8

Continuous Deployment (testability)

Then /^board should be in position (.+?)$/ do | expected_position | current_position = @client.get("#{@board}/position") current_position.content.should == expected_positionend

Continuous Deployment (testability)

Feature: change the position on board

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd8,wkd1,bke8 Then response should be 201 And board should be in position wqd8,wkd1,bke8

Scenario: change position with a correct move Given board with position wqd3,wkd1,bke8 When move to position wqd7,wkd1,bke8 Then response should be 403 And board should be in position wqd3,wkd1,bke8

Continuous Deployment (testability)coder@apollo ~/dev/cucumber/features $ cucumber change_position_on_board.feature Feature: change the position on board

Scenario: change position with a correct move # change_position_on_board.feature:3 Given board with position wqd3,wkd1,bke8 # step_definitions/change_position_on_board_steps.rb:5 When move to position wqd8,wkd1,bke8 # step_definitions/change_position_on_board_steps.rb:9 Then response should be 201 # step_definitions/change_position_on_board_steps.rb:14 And board should be in position wqd8,wkd1,bke8 # step_definitions/change_position_on_board_steps.rb:19

Scenario: change position with a correct move # change_position_on_board.feature:9 Given board with position wqd3,wkd1,bke8 # step_definitions/change_position_on_board_steps.rb:5 When move to position wqd7,wkd1,bke8 # step_definitions/change_position_on_board_steps.rb:9 Then response should be 403 # step_definitions/change_position_on_board_steps.rb:14 And board should be in position wqd3,wkd1,bke8 # step_definitions/change_position_on_board_steps.rb:19

2 scenarios (2 passed)8 steps (8 passed)

Continuous Deployment (testability)what about the view?

HTTP

Board

Game

Player

Position

Move

Js

Continuous Deployment (testability)

If i click to drag a piece, does the board highlight

reachable squares?

Continuous Deployment (testability)

Position on board is context (fixture)

We don’t care of

Model is already tested (mock)

// fixturevar piece_square = "g1"var position = "rnbqkbnr-pppp1ppp-8-4p3-4p3-8-PPPP1PPP-RNBQKBNR"

// mockvar valid_moves_url = "/position/" + position + "/piece/" + piece_square + "/moves"var YAHOO.util.Connection.asyncRequest = Chess.test.ServerMock([{ method: "GET", url: valid_moves_url, response: { code: 200 body: "moves = g1-e2, g1-f3, g1-h3" } }])

Continuous Deployment (testability)new YAHOO.tool.TestCase({ name : "testMove",

setUp: function() { this.board = Chess.board(); this.board.setupPosition(position); this.board.render("mydiv"); }, tearDown: function() { this.board.destroy(); } test_highlightReachableSquares: function() { var whiteKnight = this.board.pieceElementAt(piece_square); YAHOO.util.UserAction.mousedown(whiteKnight); this.wait(function(){ // for each g1, e2, f3, h3 YAHOO.util.Assert.isTrue( YAHOO.util.Dom.hasClass( this.board.squareElementAt("g1"), "highlight" ); ); }, 500); }}

Erlangthe secret weapon

no assignment but Pattern Matching

Continuous Deployment (testability)

1> X.* 1: variable 'X' is unbound

2> X = 5.5

3> X.5

4> X = 6.** exception error: no match of right hand side value 6

Continuous Deployment (testability)

Referentially Transparent:if a function can be

replaced with its value without changing the

program

Continuous Deployment (testability)

the function behavior is defined purely in terms of its input parameters

and return value.

Continuous Deployment (testability)

no Las Vegas

effect!

Continuous Deployment (scalability)

processes in Erlang are very cheap1> processes:profileSpawnFor(1000). Spawned 1000 processes in 10 (4) millisecondsok

2> processes:profileSpawnFor(10000). Spawned 10000 processes in 96 (40) millisecondsok

3> processes:profileSpawnFor(100000).Spawned 100000 processes in 884 (510) millisecondsok

Continuous Deployment (scalability)profileSpawnFor(Number) -> Processes = for(1, Number, fun() -> spawn(fun() -> wait() end) end), lists:foreach(fun(Pid) -> Pid ! die end, Processes).

wait() -> receive die -> void end.

Continuous Deployment (scalability)

factorials(Numbers) -> map(fun(Number) -> factorial(Number) end, Numbers).

Continuous Deployment (scalability)

factorials(Numbers) -> map(fun(Number) -> factorial(Number) end, Numbers).

factorials(Numbers) ->

pmap(fun(Number) -> factorial(Number)

end, Numbers, 20).

Distributed on20 different

processes

Continuous Deployment (scalability)

factorials(Numbers) -> map(fun(Number) -> factorial(Number) end, Numbers).

factorials(Numbers) ->

pmap(fun(Number) -> factorial(Number)

end, Numbers, 20, nodes()).

Distributed on 20 different processes for each available nodes

on the cluster

Continuous Deployment (hot-swap)

player:authorize(Request, Context).

1> c(“/home/coder/upload/player.erl”). 2> code:load_file(player).

code to update

compileand load

player:authorize(Request, Context). code updatedwithout

down-time

Continuous Deployment (hot-swap)

deploy(File) -> { ok, Module, Binary } = compile:file(File), foreach(fun(Node) -> rpc:call(Node, code, load_binary, [ Module, File, Binary ] ) end, nodes()). compile and deploy on

every node in the cluster

Conclusion

We want to create products that really satisfy our customers

... so we needa product

development methodology

... so we needa product

implementation methodology

... so we needappropriate

technologies and practices

We betterget ready because...

at the end of the day customer’s happiness is the only thing that

matters