1. Use of Scala in dwango
niconico Android API
後藤 哲志 (Satoshi Goto)
DWANGO Co.,Ltd.

2. Attention
We talk about API server
using Scala and Play
niconico Android (app) is
written by Java

3. Contents
Self-introduction (自己紹介)
Project introduction (プロジェクト紹介)
Scala pros/cons (いいところ 悪いところ)

4. Satoshi Goto
ニコニコ事業統括本部 プラットフォーム
事業本部 第一企画開発部 第４セクション
ニコニコAndroid サーバチーム所属
id:mtgto (twitter, GitHub, Qiita)

6. Works at
niconico

7. niconico is 6-year-old
PC (Windows, Mac, Linux, etc.)
Feature phone (docomo, au, softbank,
willcom)
iPhone
PS Vita
TV
WiiU
Windows 8

8. niconico is 6-year-old
PC (Windows, Mac, Linux, etc.)
Feature phone (docomo, au, softbank,
willcom)
iPhone
PS Vita
TV
WiiU ＆Android!
Windows 8

9. Project History
2012/2 Project launched
2012/8 au STB App released
2012/11 Android App released
Deployed 22 times
2.5 million requests / day

10. Our team
Planner: 1
Android developers: 5
API server developers: 6
Infra-engineers: 2

11. API server
members
@tomoyoshi_ogura
@kozo1215
@fedista
@mitikage
@kimwoonsung
@mtgto

12. API server
members
Old member
@tomoyoshi_ogura
@kozo1215
@fedista I♥
Scala
@mitikage
@kimwoonsung
@mtgto

13. Internal
API
Video
API
niconico
Android
API
Live Scala 2.9.1
API
Play 2.0

14. niconico Android API is
dwango s first service
written in Scala

15. 74 API
Video (動画)
Ranking, Search, Tags, MyList
Live (生放送)
Ranking, Search, Tags
Channel, Community, News

16. Niconico Android
is
PROXY
?

17. Niconico Android
is !
N O
PROXY
?

18. Re-defined typed model
Anticorruption LAYER (腐敗防止層)
lingo ambiguous
(社内用語) various
definition
characteristics
(曖昧な定義)
nullable

19. Why Scala ?
Increasing interests in Scala
Scala workshop in dwango
Strong compiler check
Experimental project

20. Our products
Core library
API server
Management server

21. Core
based on DDD concept
Scala (& Java enumeration)
sbt + IntelliJ IDEA (sbt-idea)
jedis (redis client) for caching
Using Java serialization
Specs 2 + Mockito

22. Open API
based on Core Library
Play 2.0.2 (JSON only)
Redis-based sessions (using jedis)
CSRF-free customized Action (Play)
Daemonized (Apache Daemon)

23. Management
based on Core Library
Play 2.0.2 (Internal web system)
Statistics and Operations
Daemonized (Apache Daemon)

24. Project scale
# of files # of tests LOC
CORE 665 976 52k
OPEN API 75 530 21k
manage 32 173 2k

25. TEST (Core)
Almost 1000
TODO: Jenkinsのスクリーンショット
TODO:テスト件数
80% Coverage

26. Pros
Option
match & sealed trait

27. Option
∼Say goodbye to NullPointerException∼

28. Null check is boring
Java
Scala

29. match
&
sealed trait

30. match

31. match

32. match
Use scalac option
-Xfatal-warnings

33. Cons
case class limitation
Jenkins server swap out
Play framework
CSRF / Akka

34. Case Class

35. Case class useful!
equals
hashCode
toString
etc.
defined
automatically!

36. Tuple22
limitation!

37. Case classes
represent XML API

38. Case classes
represent XML API
32 Elements

39. Case classes
represent XML API

40. Case classes
represent XML API
96
Elements

41. Jenkins
Swap out

42. Jenkins swap out
Scalac obtains over 1GB memory

43. Jenkins swap out
Scalac obtains over 1GB memory
Restricted the number of
simultaneous jenkins jobs...
(4 -> 2 -> 1)

44. Play / CSRF

45. CSRF self check
Implements Customized Action to
check CSRF like below:
• if Method == POST ¦ PUT ¦ DELETE
• if request.body( token ) != token
• BadRequest

46. Play / Akka

47. Request Overflowed
In production
environment, Play
causes many
exceptions

48. Request Overflowed
In production
ERROR play Cannot invoke the
action, eventually got an error:
environment, Play
Thrown(akka.pattern.AskTimeoutExc
causes many out)
eption: Timed
exceptions

49. Few documentation
for Akka...
http://www.playframework.com/documentation/2.0.4/
AkkaCore

50. Increase number of threads
from 24 to 100
Extends timeouts from 5 to 10
seconds
Almost errors aren’t occurred

51. Conclusion
We rarely faced
critical troubles
while we are using
Scala in our project

52. Thank you for listening!
https://play.google.com/
store/apps/details?
id=jp.nicovideo.android