Sustainable Agile Development

Sustainable Agile Development a case study with chess gabriele.lana@gmail.com federico.galassi@gmail.com

We have an Idea

We want to make it work

We know that Agile works in a corporate world

Can Agile work for 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) Solution: Known Requirements Design Implementation Verification Manteinance Problem: Known Eric Ries @ http://startuplessonslearned.blogspot.com/

Agile Development (Progress: Running Tested Features) Solution: Unknown quot;Product Ownerquot; or in-house customer Problem: Known Eric Ries @ http://startuplessonslearned.blogspot.com/

we should be able to Embrace Change Cost of Change Traditional Development Agile Development Time

we should be able to Embrace 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 think implementing features is real progress?

Use of Requested Features 7% 13% 45% 16% 19% The biggest source of waste is implementation of features nobody wants Standish Group, CHAOS Report 2006

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) Customer Development Solution: Unknown Problem: Unknown Eric Ries @ http://startuplessonslearned.blogspot.com/

Agile in a Waterfall world Agile Test Maintenance Concept Development Alpha/Beta and Marketing Debug, Fix and Patch

Lean Startup Development (Progress:Validated Learning about Customers) IDEAS • Reduce the LEARN BUILD cycle time Minimum • Eliminate waste Marketable Feature • Optimize the DATA CODE whole • Amplify learning MEASURE Eric Ries @ http://startuplessonslearned.blogspot.com/

How can we support the learning process?

Domain Composability: the Domain Model should be extremely ﬂexible and “exposed”

web applications Information Flow RDB HTTP OOP MS

Impedance Mismatch can slow you down RDB HTTP OOP MS Accidental Complexity

Resource Oriented Architectures HTTP ROA DATA Essential Complexity

Resource Oriented Architectures Identify Resources in your Domain

Resource Oriented Architectures Pawn Move Bishop Game Player Rank Board Rook File Knight Position Queen Square

Resource Oriented Architectures Design the URIs (Ubiquitous Language)

Resource Oriented Architectures GET /position/wqd3,wkd2,bke8 HTTP/1.1 Accept: text/plain HTTP/1.1 200 OK Content-Type: text/plain;format=fen n 5k2/8/8/8/8/3Q4/8/3K4

Resource Oriented Architectures GET /position/wqd3,wkd2,bke8 HTTP/1.1 Accept: image/png;q=0.8, text/plain;q=0.2 HTTP/1.1 200 OK Content-Type: image/png n PNG...

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 POST /board/4815162342 HTTP/1.1 n move = d3-e8 HTTP/1.1 201 Created n ... /position/wqd3,wkd1,bke8 /position/wqe8,wkd1,bke8

Resource Oriented Architectures GET /game/42 HTTP/1.1 HTTP/1.1 200 OK n board = /board/4815162342 white = /player/50298 black = /player/48192

Resource Oriented Architectures no Web Services but how the web should be

Resource Oriented Architectures Tim Berners-Lee on 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 Resource design the Representations from and to the Client

Resource Oriented Architectures GET /game/42 HTTP/1.1 Accept: 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 a Good Domain but an Ugly Interface

Ajax to rescue // Interface can have its state // but actually consumes many serverside // resources in background var game = { quot;gamequot;: quot;/game/42quot;, quot;boardquot;: quot;/board/4815162342quot;, quot;positionquot;: quot;/position/” + “rnbqkbnr-pppp1ppp-8-4p3-4P3-8-PPPP1PPP-RNBQKBNRquot; } var req = YAHOO.util.Connect.asyncRequest; req('GET', position + '/piece/g1/moves', callback); // 200 OK; moves = g1-e2, g1-f3, g1-h3 board.highlightSquares(quot;g1quot;, quot;e2quot;, quot;f3quot;, quot;h3quot;); req('POST', '/board/4815162342', callback, quot;move=g1-f3quot;); // 200 OK; position = // rnbqkbnr-pppp1ppp-8-4p3-4P3-5N2-PPPP1PPP-RNBQKB1R

John Maeda’s Laws of Simplicity Law 3: TIME Savings in time feels like simplicity. ...ok, we need real-time John Maeda @ http://lawsofsimplicity.com

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

But which Comet way? Transport API Long polling Socket Forever Frame Publish/Subscribe Script tags API based WebSockets Data sync Htmlﬁle REST? Mime Messaging Flash Remoting Joe Walker @ http://www.slideshare.net/joewalker/comet-and-the-rise-of-highly-interactive-websites-presentation

HTTP Channels is RESTful Comet “The primary purpose of HTTP Channels Kris Zyp: 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 @ http://cometdaily.com/2008/06/05/intended-usage-of-http-channels/

Http Channels 2 POST /channels HTTP/1.1 Accept: application/http X-Create-Client-Id: 123123 GET /foo HTTP/1.1 Accept: */* X-Subscribe: * X-Client-Id: 123123 PUT /foo HTTP/1.1 n { data: “foobar” } HTTP/1.1 200 OK X-Event: PUT Content-Location: /foo n { data: quot;foobarquot; } Kris Zyp @ http://cometdaily.com/2008/05/13/http-channels-2/

Http Channels 3 X-Client-Id: 123123 POST /board/4815162342 HTTP/1.1 n move = g1-f3 HTTP/1.1 200 OK X-Event: POST Content-Location: /board/4815162342 n move = g1-f3 X-Client-Id: 124124 X-Client-Id: 125125 X-Client-Id: 126126

How can we speed up the learning process?

Continuous Deployment reduces the time from code check-in to production

Continuous Deployment Testability tells if it’s a good change or a bad change as quickly as possible

Continuous Deployment (testability) View Model Control HTTP

Continuous Deployment (testability) too much code untested View Model Control HTTP

Continuous Deployment (testability) too fragile and unreliable View Model Control HTTP

Continuous Deployment (testability) Ruby with Rspec and Cucumber Player Board Position Game Move Js HTTP

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

Continuous Deployment (testability) 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 When /^move to position (.+?)$/ do | to_position | move_reponse = @client.post(@board, quot;position = #{to_position}quot;) @move_response_status = move_response.status end

Continuous Deployment (testability) 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 Then /^response should be (d{3})$/ do | expected_response_status | @move_response_status.should == expected_response_status end

Continuous Deployment (testability) 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 Then /^board should be in position (.+?)$/ do | expected_position | current_position = @client.get(quot;#{@board}/positionquot;) current_position.content.should == expected_position end

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? Player Board Position Game Move Js HTTP

Continuous Deployment (testability) If i click to drag a piece, does the board highlight reachable squares?

Continuous Deployment (testability) We don’t care of Position on board Model is already is context (ﬁxture) tested (mock) // fixture // mock var piece_square = quot;g1quot; var valid_moves_url = quot;/position/quot; + position + var position = quot;/piece/quot; + piece_square + quot;rnbqkbnr-pppp1ppp-8-4p3-4p3-8-PPPP1PPP-RNBQKBNRquot; quot;/movesquot; var YAHOO.util.Connection.asyncRequest = Chess.test.ServerMock([{ method: quot;GETquot;, url: valid_moves_url, response: { code: 200 body: quot;moves = g1-e2, g1-f3, g1-h3quot; } }])

Continuous Deployment (testability) new YAHOO.tool.TestCase({ name : quot;testMovequot;, setUp: function() { this.board = Chess.board(); this.board.setupPosition(position); this.board.render(quot;mydivquot;); }, 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(quot;g1quot;), quot;highlightquot; ); ); }, 500); } }

Erlang the secret weapon

Continuous Deployment (testability) no assignment but Pattern Matching 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 cheap 1> processes:profileSpawnFor(1000). Spawned 1000 processes in 10 (4) milliseconds ok 2> processes:profileSpawnFor(10000). Spawned 10000 processes in 96 (40) milliseconds ok 3> processes:profileSpawnFor(100000). Spawned 100000 processes in 884 (510) milliseconds ok

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) -> Distributed on factorial(Number) 20 different processes end, Numbers, 20).

Continuous Deployment (scalability) factorials(Numbers) -> map(fun(Number) -> factorial(Number) end, Numbers). Distributed on 20 different processes for factorials(Numbers) -> each available nodes on the cluster pmap(fun(Number) -> factorial(Number) end, Numbers, 20, nodes()).

Continuous Deployment (hot-swap) player:authorize(Request, Context). code to update 1> c(“/home/coder/upload/player.erl”). compile 2> code:load_ﬁle(player). and load player:authorize(Request, Context). code updated without 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 need a product development methodology

... so we need a product implementation methodology

... so we need appropriate technologies and practices

We better get ready because...

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

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Sustainable Agile Development

by Gabriele Lana on May 11, 2009

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Sustainable Agile Development — Presentation Transcript