Applications get old, and technology moves fast. Overtime, adding or modifying functionalities might become as expensive as re-coding everything all from scratch. But rewriting a complete website and its functionalities it’s hard if we want to minimize the risks of breaking existing functionalities and specially when this application fits in a ecosystem and interacts with other pieces of software and teams. In this session, you will learn how we moved from a legacy java monolithic website using scala PlayFramework, AngularJS, Elasticsearch and MongoDB, how we built a multi service and REST oriented architecture, which were the technical and human problems we encountered and how we managed to solved them.

1. How and why we evolved a
legacy java application to scala
And we are still alive !
24/06/2015

2. I am
@karesti

3. The Software Dream

4. Software is more like Madonna

5. FACTS

6. Web applications get old (very) fast

7. Continuous small refactoring does
not avoid long-term technical debt

8. From strach Refactoring
Continuous Dilemma

9. 2014

10. French Job Search Website
Launched in 2000

11. 2008

12. Problems in 2014

13. High Cost Adding New Functionalities
High Technical Debt

14. Coupled Architecture
S O A
Spaghettis Oriented Architecture

15. Lack of real KPI

16. In a 100% Linux Environment

17. Monolithic Architecture

18. DAO
ServiceBatch
MVC
RDMS

19. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter

20. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter
Jobs

21. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter
Jobs
Jobs
External
App

22. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter
Jobs
Jobs
External
App
Connected User Board
CV, Mail Alert, Newsletter

23. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter
Jobs
Jobs
External
App
Data
Mailing
App
Connected User Board
CV, Mail Alert, Newsletter

24. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter
Jobs
Jobs
External
App
Data
Mailing
App
External
App
Connected User Board
CV, Mail Alert, Newsletter

25. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter
Jobs
Jobs
External
App
Data
Mailing
App
External
App
Mobile
Version
Connected User Board
CV, Mail Alert, Newsletter

26. DAO
ServiceBatch
MVC
RDMS
Anonymous User
Job Search, Detail, Newsletter
Jobs
Jobs
External
App
Data
Mailing
App
External
App
Mobile
Version
Connected User Board
CV, Mail Alert, Newsletter

27. DAO
ServiceBatch
MVC
RDMS
External
App
Connected User Board
CV, Mail Alert, Newsletter
Anonymous User
Job Search, Detail, Newsletter
Non connected
Alerts, Newsletter
Jobs
Jobs
External
App
Data
Mailing
App
Mobile
Version
Partners

28. How do we fix this

29. Target

31. Where do we start

32. DAO
ServiceBatch
MVC
RDMS
External
App
Jobs
Jobs
External
App
Data
Mailing
App
Mobile
Version
Partners
Connected User Board
CV, Mail Alert, Newsletter
Anonymous User
Job Search, Detail, Newsletter
Non connected
Alerts, Newsletter

33. Mars – September 2014
User Board

34. DAO
ServiceBatch
MVC
RDMS
Data
Mailing
App
User Board
User Board
Front-End
REST API
Mongo

35. DAO
ServiceBatch
MVC
RDMS
Data
Mailing
App
Where do we start ?
User Board
Front-End
REST API
Mongo
Partners

36. DAO
ServiceBatch
MVC
RDMS
Data
Mailing
App
Where do we start ?
User Board
Front-End
REST API
Mongo
Partners

37. DAO
ServiceBatch
MVC
RDMS
Data
Mailing
App
Where do we start ?
User Board
Front-End
REST API
Mongo
Partners

38. DAO
ServiceBatch
MVC
RDMS
Data
Mailing
App
Where do we start ?
User Board
Front-End
REST API
Mongo
Partners
External
App

39. DAO
ServiceBatch
MVC
RDMS
Data
Mailing
App
Where do we start ?
User Board
Front-End
REST API
Mongo
Partners
External
App

40. DAO
ServiceBatch
MVC
RDMS
Data
Mailing
App
Where do we start ?
User Board
Front-End
REST API
Mongo
Partners
External
App
Data
Batch

41. API First

42. Macro

43. Operation

44. Focus on technical choices

45. Main Language
• Growing and Solid Community
• Powerful Frameworks and Utilities
• JVM

46. Backend
• REST oriented
• Template Type Safe
• Hot Reloading
• “Simplifies” Scala
• Reactive programming

47. Batch System
• Actors
• Scale Up – concurrency
• Scale Out – remoting
• Fault Tolerance

48. Front End
• Sass built in with play
• AngularJS, popular, community, experience
• Foundation, solid and easy CSS framework

49. Database
• Flexible schema
• Document oriented makes sense with CVs
• Low transactions
• Application code rules the database schema
– Already the case with SQL Server
• No DBA*
– We rule the database as dev

50. Migrating Data Challenge

51. Status
• +10 years of candidate data
• Crucial for business
• Cannot fail  really, C A N O T F A I L !!

52. Strategy
• Start migration as soon as possible
– Started in April – Mai
• Migrate data incrementally
• Verify as much as possible
• Legacy ID

53. Akka Actors
• One actor per data
• Concurrence execution when possible
• Handle updates for the crucial moment =>
between SQL Server Stop and MongoDB Up

54. Madrid MUG
This section is specially dedicated to
the Madrid MUG Members

55. SQL Model
• 8 tables for the user profile
• Complex joins
• SQLServer => Lost in a Linux World
• Devs => Backup, dump …

56. (Very) Simplified Schema

57. MongoDB Model
• 1 document / profile
• Object <> Document
• Simplified model
– Option Scala
• Using Reactive Mongo Driver
• Using Jongo in Java

58. Mongo Collections

59. Model choices
• ++ reads / -- writes
• Stable Reference data *
– Sometimes sectors can change…
• Low and non risky transactions
– Ex : user deletes account

60. Testing

61. Unit Testing
• Using Specs framework
• Using Mockito
– Not as useful as in Java 
• Some tests are not necessary
– Constructors, Builders … Scala Type Safe and
Immutability

62. Testing the Front END
• Unit testing JS with Karma 
• Selenium 
– Very fragile tests
– Proxy Nightmare
– Endless navigator problems
– Just vital tests after production

63. API Tests are CRUCIAL

64. Testing the REST API
• No Mocking MongoDB
• Using Embedded Mongo
• Start and Stop Mongo once for every test
– DRY data is a hard part
https://github.com/flapdoodle-oss/de.flapdoodle.embed.mongo

65. Always thinking on KPI

66. Build Measure Learn

67. SCALA USER GROUP
This section is specially dedicated to the Madrid Scala User Group.
Thank you to Nouhoum Traoré who spoke about it at scala.io in Paris

68. Front-end
● Client API
● No DB Access
● Mostly Javascript Code

69. Front-end
● 9 % Scala
● 26.2 % CSS
● 64.8 % JS

70. Le frontend : asset pipeline
pipelineStages := Seq(rjs, digest, gzip)

71. Le frontend : asset pipeline
curl http://keljob.com/assets/js/e454f1013e30b783818c8efaf3a8e3a5-startup.js
HTTP/1.1 200 OK
Cache-Control: public, max-age=31536000
Content-Length: 171997
Content-Type: application/javascript; charset=utf-8
Date: Tue, 14 Oct 2014 22:39:23 GMT
ETag: e454f1013e30b783818c8efaf3a8e3a5
Last-Modified: Wed, 08 Oct 2014 12:35:10 GMT

72. Compressing content
import play.api.mvc._
import play.filters.gzip.GzipFilter
object Global extends WithFilters(new GzipFilter()) {
...
}

73. API : links on JSON
implicit val AccountWrites = new Writes[Account] {
override def writes(account: Account): JsValue =
Json.obj(
"id" -> account.id,
"email" -> account.email,
"creationDate" -> account.creationDate.toString(),
"links" -> Json.obj(
"self" -> routes.AccountDetailCtrl.get(account.id).url,
"alerts" -> routes.JobAlertDetailCtrl.getAlertsOf(account.id).url,
"cv" -> routes.CvDetailController.getCvOf(account.id).url
)
)
}

74. Single responsibility Object :
Controllers
@Singleton
class AccountValidationController @Inject() (
accountValidator: AccountValidator) extends Controller {
def validateAccount(token: String) = Action.async { request =>
accountValidator.validate(token).map {
case Some(account) => Ok(Json.toJson(account))
case _ => UnprocessableEntity(Json.toJson(InvalidToken))
}
}

75. Single responsibility Object :
Services
class AccountAuthenticator @Inject() (...)
class AccountValidator @Inject() (...)
class AccountCreator @Inject() (...)
class AccountSettingsUpdater @Inject() (...)

76. Single Responsibility Object : Actors
import akka.actor._
...
class CvExporter(...) extends Actor {
def commonBehavior(): Receive = ???
def deleteBehavior(): Receive = ???
def updateBehavior(): Receive = ???
def receive = commonBehavior orElse updateBehavior orElse deleteBehavior
}

77. Error Handling in Services
sealed trait NewsletterError
case object InvalidNewsletterActivationToken extends NewsletterError
case object NewsletterUpdateError extends NewsletterError
class NewsletterActivator @Inject() (...) {
def activate(code: String): Future[Either[NewsletterError, Boolean]] = ???
}

78. Error handling in controllers
class NewsletterActivationController (
newsletterActivor: NewsletterActivator) extends Controller {
def activate(token: String) = Action.async { request =>
newsletterActivor.activate(token).map {
…
case InvalidNewsletterActivationToken => ???
case NewsletterUpdateError => ???
…
}.recoverApiError("Oops !!!")
}
}

79. Error handling in controllers
implicit class ApiErrorRecover(result: Future[Result]) {
def recoverApiError(message: String) =
result recover {
case NonFatal(e) => InternalServerError(
Json.toJson(SimpleError(message))
)
}
}

80. The Team

81. The (original) Team
• 3 Developers and a Product Owner
– Legacy + Backend + Scala
– Full-Stack
– Java + Backend + MongoDB
• From 5-10 years of experience
• People who are able to leave their confortable
coding zone
• Want to communicate

82. Project Management
Method

83. SCRUM

84. KANBAN

85. Programing MF

86. (SOME) DIFFICULTIES

87. DEFINING THE INITIAL
SCOPE

88. MVP

89. MVP

90. Maximal Viable Product

91. DEALING WITH NO
TECHNICAL PEOPLE

93. Demo

94. We have a situation …

95. Y
FIF Pattern
Fancy Interface First

96. SCALA
Warning ! This section might contain some trolls

97. Personal journey to Scala

98. SIMPLE ??? Build Tool
"de.flapdoodle.embed" %
"de.flapdoodle.embed.mongo" % "1.46.0”
"org.mongodb" %% "casbah" % "2.5.0"

99. Reactive Futures …

100. Implicits
accountFuture.filter(_.isDefined).map(_.get)

101. Cake Pattern

102. DI Framework vs Cake Pattern
@Singleton
class LoginController @Inject()
(accountAuthenticator: AccountAuthenticator)
extends Controller
trait LoginController { this: Controller with
UserServiceComponent =>
object LoginController extends LoginController with
Controller with MongoDbUserServiceComponent

103. Loving Case Class And Constructors
case class Account(
id: Option[BSONObjectID] = None,
email: String,
creationDate: DateTime,
optin: Boolean = false,
optoutScenario: Option[DateTime] = None,
source: String = Account.DEFAULT_SOURCE,
deletionDate: Option[DateTime] = None)
Account(“chucknorris@gmail.com”,
creationDate = creationDate,
optin = true)

104. After 2-3 months as happy as being at
Machu Picchu

105. Loving both … 

106. September – December 2014

107. Once in production
– Creating accounts more easily
– Parsing CV on upload
– Can apply with the CV
– Follow applications
• And other awesome stuff built fast and
furiously !

108. January – March 2015
Search and Relooking

109. Relooking and positioning

110. BatchData
Mailing
App
2015
Web Front-
End
User REST
API
Mongo
Partners
in WIP
External
App Data
Search REST
API
Elastic
Search
Batch

111. SEO
Most Important Challenge

112. Challenge 2 : Performance
• Gatling
– Play! 
• Comparing performance