Why it's cool for everyone and what is the current state. Everybody has something about streams on scala platform : Iteratee, scalaz.streams, Reactive streams, akka.io… But is it usefull for day to day developper job? Is it only for database drivers? What is the differences between all this technologies? So, why you need streams in your app, understand what is it and use it in real world.

1. STREAMS ON
TOP OF SCALA
BY @WAXZCE – QUENTIN ADAM
SCALAR 2015 WARSAW

2. Quentin ADAM from the Clever Cloud
@waxzce on twitter – github- soundcloud – instagram ….
WHO AM I ?

3. MY DAY TO DAY WORK :
CLEVER CLOUD, MAKE YOUR
APP RUN ALL THE TIME

4. And learn a lot of things about your code, apps, and good/bad design…
KEEP YOUR APPS ONLINE. MADE WITH
NODE.JS, SCALA, JAVA, RUBY, PHP,
PYTHON, GO OR DOCKER…

5. AND LEARN A LOT OF THINGS ABOUT
YOUR CODE, APPS, AND GOOD/BAD
DESIGN…

6. WHY ARE STREAMS SO
TRENDY THESE DAYS?

7. 2 MAIN
REASONS

8. DATA IS BECOMING
BIGGER AND BIGGER

9. WE NEED TO ACT WHILE
DATA TRANSFERRING IS
OCCURRING

10. &

11. WE ARE NOW USING
LOTS OF PERMANENT
CONNECTIONS

12. REALITY FOR
MANY
DEVELOPERS

13. WEBSOCKETS

14. HTTP/2

15. EXAMPLE

16. WHAT IS INSIDE AN
HTTP REQUEST ?
Verb
• The action
Resource
• The object of the action
Headers
• The context of the action
Body
• Optional
• The datas

17. IN MANY CASES THE REQUEST IS
MANIPULATED ALL FROM MEMORY

18. UPLOADING A
20 GB FILE ON
A POST
REQUEST
AND STORING IT
EXAMPLE

19. IT’S A BAD IDEA TO PUT THE BODY
PART IN MEMORY

20. CREATE A TEMP FILE TO STORE THE
DATA

21. I HATE FILE
SYSTEMS

22. I HATE FILE
SYSTEMS

23. DO NOT USE THE FILE
SYSTEM AS A DATASTORE
File systems are POSIX compliant
• POSIX is ACID
• POSIX is powerful but is a bottleneck
• File System is the nightmare of ops
• File System creates coupling (host provider/OS/language)
• SPOF-free multi tenant File System is a unicorn

24. Client
uploads
file
Create a
temp file
Send a
file in a
backend
Then
answer to
the client
The file is
transferring two
times

25. NOT SO GOOD

26. Client
uploads file
Directly
stream it to
the backend
Then
answer to
the client

27. LET’S ACT ON STREAMS!

28. CLASSIC JAVA STREAM
MANAGEMENT

29. HUM…

30. CLASSIC JAVA STREAM
MANAGEMENT
• Buffers
• Buffer management
• Buffer exception
• Buffer overflow

32. CLASSIC JAVA STREAM
MANAGEMENT
• Low performances if not buffered
• Not modular
• Thread blocking
• Code is ugly
• No back pressure
• Error handling is bad
• i/o management and business code are mixed

33. I CAN’T SLEEP AT NIGHT

34. WE HAVE TO FIND A BETTER WAY

35. DATA
STRUCTURES
TO EXPRESS
DATA STREAM
MANAGEMENT

36. PLAY-
ITERATEES
FIRST OPTION

37. Like a recipe
Consume the data
ITERATEE : HOW TO MANAGE A STREAM

38. Produce the data
ENUMERATOR : DATA STREAM

39. Set of tools to do cool things with Iteratee and Enumerator
ENUMERATEE

40. SIMPLE EXAMPLE TO START

41. WHAT’S OUR GOAL
• Get Reactive Manifesto words
• Stream it to an iteratee to group it by pair of word
• Print it

42. AN ENUMERATOR

43. AN ITERATEE

44. input
EOF
EmptyEl

45. Iteratee
State
Done
ErrorCont

46. AN ITERATEE

47. AN ITERATEE TO
MANAGE THE STREAM

49. AN ITERATEE

51. ITERATEE
COMPOSITION

53. PURELY FUNCTIONAL

54. TYPE SAFE

55. COMPOSITION

56. - Engine is hard to build
- Not bidirectional
BUT IT’S DYING

57. WHAT’S
TRENDY?
BUT ITERATEES ARE GOING TO DIE

58. SCALAZ STREAMS

59. WHAT’S IN
THE BOX ?

60. BASED ON SCALAZ
BASICS

61. PROCESS IS KEY

62. SIMPLY USE THE
COLLECTION API

63. DEMO

64. BINDINGS WITH
• http with (netty or http4s)
• scodec
• …

65. BUT WE NEED TO TALK WITH OTHERS…

66. LIKE OUR
FRIENDS
ON TOP OF
JVM

67. AND THEY
HAVE LESS
EXPRESSIVE
TYPE
SYSTEM

68. + POLITICS

69. + POLITICS

70. REACTIVE
STREAMS
ENTER

71. JVM
UNIFIED
WAY FOR
STREAMS

72. I/O
PLUMBERY
&
PROCESS

73. USE STREAM AS PROCESS MODELING

74. AKKA
STREAMS
CURRENT 1.0-M5 (MILESTONE) (M5 OUT
YESTEDAY)

75. BASED ON AKKA ACTOR SYSTEM

76. BASIC EXAMPLE

77. BASIC EXAMPLE

78. DEMO AGAIN

79. MORE POSSIBILITIES
Grab from
rabbitMQ
Parse Event
Check event
ACL from
DB
Find reliable
WS
Send data to
WS

80. BINDINGS WITH
• Akka i/o HTTP
• rabbitMQ
• Many databases….
• Very easy to write a Sink/Source with actors

81. MAKE BUSINESS PROCESS
BATTERY INCLUDED

82. ARE YOU CONVINCE
TO USE STREAM ?

83. GO NOW
Iteratee
Scalaz-
streams
Akka-
stream
• learn
• Act now on play!
• Beautiful design
• The most scala-ish
way to do
• Enterprise compatible
• Wide ecosystem
• Reactive stream
ready

84. DATA STREAMING
PROGRAMMING IS NOW
TRENDING

85. THX TO @CLEMENTD
CLEMENT DELAFARGUE

86. I’m @waxzce on twitter
I’m the CEO of
A PaaS provider, give it a try
;-)
THX FOR LISTENING
& QUESTIONS TIME
Coupon for Clever Cloud trial :
scalariscool