Adam Polak: Websockety już na stałe zagościły w naszych systemach. Jeżeli gdzieś widzimy frazę “real-time app” to od razu wiemy, że prawdopodobnie mamy do czynienia z tym typem komunikacji. Tym razem, wspólnie przejdziemy przez wszystkie aspekty tworzenia aplikacji czasu rzeczywistego w JS. Będzie o tym jak zacząć, na co zwrócić uwagę oraz w jaki sposób skalować aplikacje tego typu.

1. WEBSOCKETS 101

2. ADAM POLAK
HEAD OF NODE.JS @ THE SOFTWARE HOUSE
ADAM.POLAK@TSH.IO
POLAK.ADAM1

3. HISTORY OF
COMMUNICATION

4. REST

5. ▸ STANDARIZED
▸ HTTP BASED
▸ STATELESS
▸ EASY TO SCALE
▸ BUILT AROUND CRUD
WEBSOCKET 101
REST PROS/CONS

6. STANDARIZED

7. UNIFORMED INTERFACE
{SERVER}/{RESOURCE}/{ID}/{SUB-RESOURCE}

8. HTTP://MY.API.COM/USERS/123
HTTP://MY.API.COM/USERS
HTTP://MY.API.COM/USERS/123/TRANSACTIONS
EXAMPLES

9. HTTP METHODS
GET - READ
POST - CREATE
PUT/PATCH - UPDATE
DELETE- REMOVE
HEAD- EXISTS

10. CREATE NEW USER
POST HTTP://MY.API.COM/USERS

11. GET LIST OF USERS
GET HTTP://MY.API.COM/USERS

12. GET SINGLE USER
GET HTTP://MY.API.COM/USERS/123

13. COMPLEX PROCESSES
ARE HARD TO IMPLEMENT

14. *-RPC

15. ▸ MULTIPLE IMPLEMENTATIONS (JSON-RPC, gRPC)
▸ CONTRACT BASED
▸ MOSTLY STATELESS
▸ EASY TO SCALE
▸ SINGLE ENTRY POINT
WEBSOCKET 101
*-RPC PROS/CONS

16. CONTRACT

17. CONTRACT

18. SINGLE ENTRY POINT

19. /API

20. REAL-TIME?KINDA

21. WEBSOCKET!

22. ▸ NOT STANDARIZED
▸ STATEFUL SERVERS
▸ HARDER TO SCALE
▸ SINGLE ENTRY POINT
WEBSOCKET 101
WEBSOCKET PROS/CONS

23. CLEAN ARCHITECTURE?

24. REST
POST HTTP://MY.API.COM/USERS

25. WHAT ABOUT
*-RPC AND WEBSOCKET?

26. NO BUILT-IN SEPARATION
SINGLE ENTRY POINT

27. *-RPC
/API

28. WEBSOCKET
WS://MY-SOCKET:5555

29. LET’S USE SWITCH!

30. TIP #1INTRODUCE CONTRACT

31. CONTRACT
FOR BOTH REQ AND RES

32. TIP #2COMMAND PATTERN

33. MESSAGE COMMAND HANDLER

34. COMMAND
??
HANDLER

35. COMMAND BUS

36. ENTRY POINT

37. HOW TO SEND MESSAGE
TO CLIENTS?

38. TIP #3MESSAGING

39. INTERNAL MESSAGINGRX.JS SUBJECT

40. LET’S CREATE STREAM

41. AND USE IT TO PUBLISH MESSAGES

42. SUBSCRIBE AND SEND TO CLIENTS

43. HANDLER = LOGICONLY!

44. WHAT ABOUT
SCALING?

45. VERTICAL
HORIZONTAL
MORE RAW POWER
LESS RAW POWER
MORE INSTANCESLESS INSTANCES

46. HORIZONTAL IS BETTER
THAN VERTICAL

47. HORIZONTAL IS EASY
WITH STATELESS

48. WEBSOCKET IS
STATEFUL!

49. OPTION #1
SCALE VERTICALY

50. SOLUTION #1
SOCKETCLUSTER

51. OPTION #2
SCALE HORIZONTALY

52. SOLUTION #2
PROXY + STICKY SESSION

53. TIP #4USE HAPROXY FOR SCALING

54. LOAD BALANCER
BACKEND #1
BACKEND #2
BACKEND #3
FRONTEND PROXY

55. BASIC PROXY CONFIG

56. DEFAULT SETTINGS

57. ENTRY POINT FOR REQUESTS

58. POSSIBLE FRONTENDS

59. WEBSOCKET PROXY ISSUE
SOCKET PROXY
CONNECTION OK
NOT EXISTING
CONNECTION
BACKEND #1
BACKEND #2

60. STICKY SESSION

61. SOCKET IS BOUND TO
SINGLE BACKEND

62. STICKY SESSION CONFIG

63. CREATE COOKIE WITH
SERVERID FOR CONNECTION

64. BIND SERVER TO SPECIFIC
COOKIE VALUE

65. PROBLEM SOLVED?ALMOST

66. INTER SERVER COMMUNICATION ISSUE
SOCKET #1
PROXY
BACKEND #1
BACKEND #2SOCKET #2

67. BROADCAST ISSUE
SOCKET #1 IS CONNECTED TO BACKEND #1
BACKEND #1 CAN BROADCAST TO SOCKET #1
BACKEND #1 HAS NO IDEA ABOUT SOCKET #2
BACKEND #2 KNOWS ABOUT SOCKET #2

68. INTER SERVER MESSAGING
PUB/SUB

69. SEND EVERY MESSAGE TO CHANNEL
REDIS, DEMOCRACY, KAFKA ETC.

70. SUBSCRIBE TO CHANNEL AND
RESEND TO CONNECTED SOCKETS

71. FINALLY!

72. ▸ ALWAYS USE CONTRACTS FOR REQ AND RES
▸ USE COMMAND PATTERN FOR CLEANER
ARCHITECTURE
▸ USE HAPROXY FOR HORIZONTAL SCALING
▸ YOU CAN USE HAPROXY FOR STICKY SESSION
TOO
▸ IN CASE OF STICKY SESSION YOU NEED TO HAVE
MESSAGE BROKER
WEBSOCKET 101
SUMMARY

73. THANK YOU!

74. QUESTIONS ?

75. Linkletter.
Najbardziej wyluzowany
newsletter dla programistów.
TSH.io/linkletter