Everybody has something about streams on the Scala platform: iteratee, scalaz.streams, reactive streams, akka.io, and so on. But are they useful for the day to day developer job? Are they only for database drivers? What are the differences between all this technologies? You will understand what are streams, why you need them and how to use them in real world scenarios

1. STREAMS ON
TOP OF SCALA
BY @WAXZCE – QUENTIN ADAM
LAMBDACON 2015 BOLOGNA

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

30. 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

31. I CAN’T SLEEP AT NIGHT

32. WE HAVE TO FIND A BETTER WAY

33. DATA
STRUCTURES
TO EXPRESS
DATA STREAM
MANAGEMENT

34. PLAY-
ITERATEES
FIRST OPTION

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

36. Produce the data
ENUMERATOR : DATA STREAM

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

38. SIMPLE EXAMPLE TO START

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

40. AN ENUMERATOR

41. AN ITERATEE

42. input
EOF
EmptyEl

43. Iteratee
State
Done
ErrorCont

44. AN ITERATEE

45. AN ITERATEE TO
MANAGE THE STREAM

47. AN ITERATEE

49. ITERATEE
COMPOSITION

51. PURELY FUNCTIONAL

52. TYPE SAFE

53. COMPOSITION

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

55. SCALAZ STREAMS

56. WHAT’S IN
THE BOX ?

57. BASED ON SCALAZ
BASICS

58. PROCESS IS KEY

59. SIMPLY USE THE
COLLECTION API

60. DEMO

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

62. BUT WE
NEED TO
TALK WITH
OTHERS…

63. LIKE OUR
FRIENDS
ON TOP OF
JVM

64. AND THEY
HAVE LESS
EXPRESSIVE
TYPE
SYSTEM

65. + POLITICS

66. REACTIVE
STREAMS
ENTER

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

68. BASIC EXAMPLE

69. BASIC EXAMPLE

70. DEMO AGAIN

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

72. ARE YOU CONVINCE
TO USE STREAM ?

73. 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

74. DATA STREAMING
PROGRAMMING IS NOW
TRENDING

75. THX TO @CLEMENTD
CLEMENT DELAFARGUE

76. 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 :
lambdacon