This document discusses various mechanisms for syncing data between clients and servers in real-time, including polling, Comet, long polling, websockets, and Engine.IO. It then provides an overview of Firebase, a backend service that allows saving and syncing data in real-time. Firebase allows developing apps using only client-side code, integrating apps with servers, or adding real-time features to existing apps. The document addresses common questions about Firebase's enterprise offerings and data export options.

1. Firebase introduction
Kewang

2. 2
Live DEMO
https://db.tt/40igKVhc

3. 3
Agenda
● Variety of sync mechanisms
● Firebase

4. Variety of sync mechanisms
4

5. 5
Variety of sync mechanisms
● Polling
● Comet
● Long Polling
● WebSocket
● Engine.IO (Socket.IO)
● Polling & Push

6. 6
Polling
send scheduling request

7. 7
Polling
client server

8. 8
Polling
client server
T0
T1
T2

9. 9
Polling
client server
T0
T1
T2
T4
T5
T6

10. 10
Polling
client server
T0
T1
T2
T4
T5
T6
T8
T9
T10

11. 11
Polling
● Pros
– Easy to implement
● Cons
– No efficiency

12. 12
Comet
a never died HTTP request

13. 13
Comet
client server

14. 14
Comet
client server
T0
T1

15. 15
Comet
client server
T0
T1

16. 16
Comet
client server
T0
T1
T3
T2

17. 17
Comet
client server
T0
T1
T3
T6
T2
T5

18. 18
Comet
client server
T0
T1
T3
T6
T8
T2
T5
T7

19. 19
Comet
client server
T0
T1
T3
T6
T8
T12
T2
T5
T7
T11

20. 20
Comet
● Pros
– Save more network traffic
● Cons
– Blocking IO issue
– Always get server response, can't send another request

21. 21
Long Polling
send a long time request repeatedly
when response received

22. 22
Long Polling
client server

23. 23
Long Polling
client server
T0
T1

24. 24
Long Polling
client server
T0
T1

25. 25
Long Polling
client server
T0
T1
T4
T3

26. 26
Long Polling
client server
T0
T1
T4
T3
T5

27. 27
Long Polling
client server
T0
T1
T4
T3
T5

28. 28
Long Polling
client server
T0
T1
T4
T3
T5
T21
T20

29. 29
Long Polling
● Pros
– Save a little network traffic
– Can send another request
● Cons
– I don't know

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WebSocket
FDX communications channels
over a single TCP connection

31. 31
WebSocket
client server

32. 32
WebSocket
client server

33. 33
WebSocket
client server
T0
T1
T2

34. 34
WebSocket
client server
T0
T1
T2
T3
T4
T5

35. 35
WebSocket
client server
T0
T1
T2
T3
T4
T5
T9
T10
T11

36. 36
WebSocket
client server
T0
T1
T2
T3
T4
T5
T17
T18
T19
T9
T10
T11

37. 37
WebSocket
● Pros
– Bidirectional communication
– Save more network traffic
● Cons
– Proxy & Firewall issue

38. 38
Engine.IO
communication layer for Socket.IO

39. 39
Engine.IO - Socket.IO history
0.1~0.6.2 0.6.3~0.6.17 0.7.0~0.9.17 1.0.0~now
websocket ✓ ✓ ✓ ✓
server-events ✓
flashsocket ✓ ✓ ✓
htmlfile ✓ ✓
xhr-multipart ✓ ✓
xhr-polling ✓ ✓ ✓
jsonp-polling ✓
polling ✓

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Engine.IO - Overview

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Engine.IO - Overview
● Ensure the most reliable realtime communication

42. 42
Engine.IO - Overview
● Ensure the most reliable realtime communication
● Always establishes a long-polling connection first

43. 43
Engine.IO - Overview
● Ensure the most reliable realtime communication
● Always establishes a long-polling connection first
– then tries to upgrade to better transports that are
"tested" on the side

44. Engine.IO - Upgrade transport seamlessly
44

45. Engine.IO - Upgrade transport seamlessly
45
● Switches from polling to another transport in
between polling cycles

46. Engine.IO - Upgrade transport seamlessly
46
● Switches from polling to another transport in
between polling cycles
● To ensure no messages are lost, the upgrade packet
will only be sent once all the buffers of the existing
transport are flushed and the transport is
considered paused

47. 47
Engine.IO
client server

48. 48
Engine.IO
client server
T0
T1

49. 49
Engine.IO
client server
T0
T1

50. 50
Engine.IO
client server
T0
T1

51. 51
Engine.IO
client server
T0
T1
T6
T5
T7

52. 52
Engine.IO
client server
T0
T1
T11
T6
T5
T7
T10

53. 53
Engine.IO
client server
T0
T1
T11
T6
T5
T7
T10

54. 54
Engine.IO
client server
T0
T1
T5
T7
T11
T6
T12
T13
T14
T10

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Engine.IO
● Pros
– Auto-switch different network scenario
● Cons
– Use particular protocol at server & client

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Polling & Push
simple sync mechanism

57. 57
Polling & Push - Push off
client server

58. 58
Polling & Push - Push off
client server
T0
T1
T2

59. 59
Polling & Push - Push off
client server
T0
T1
T2
T4
T5
T6

60. 60
Polling & Push - Push off
client server
T0
T1
T2
T4
T5
T6
T8
T9
T10

61. 61
Polling & Push - Push on
client server SNS

62. 62
Polling & Push - Push on
client server
T0
T1
T2
SNS

63. 63
Polling & Push - Push on
client server
T0
T1
T2
T22
T23
T24
SNS

64. 64
Polling & Push - Push on
client server
T0
T1
T2
T22
T23
T24
SNS
T30

65. 65
Polling & Push - Push on
client server
T0
T1
T2
T22
T23
T24
T31
T32
T33
SNS
T30

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Polling & Push
● Pros
– Easy to implement
● Cons
– No (official statement)

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Firebase

68. 68
Firebase
● Save data in the cloud
● Realtime Data
● Easy authentication
● Bulletproof Security
● Instant Scalability

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Pattern 1 - Client Only

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Pattern 1 - Client Only
● Developing a brand new application
● Needs minimal integration with legacy systems or
other third party services
● App doesn’t have heavy data processing needs or
complex user authentication requirements

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Pattern 2 - Client & Server

72. 72
Pattern 2 - Client & Server
● To integrate with third party APIs
● Advanced authentication requirements
● Can’t run computationally intensive code on a
client, or requires code to run on a trusted server

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Pattern 3 - Existing App

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Pattern 3 - Existing App
● An existing full-featured app, and aren’t planning a
rewrite
● Codebase is large and cannot change
● Add realtime features without touching the rest of
app

75. 75
Live DEMO2

76. 76
FAQ

77. 77
FAQ
● Enterprise solution

78. 78
FAQ
● Enterprise solution
– Custom SLA
– 24*7 support
– Dedicated clusters
– Training

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FAQ
● Enterprise solution
– Custom SLA
– 24*7 support
– Dedicated clusters
– Training
● Concurrent connection

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FAQ
● Enterprise solution
– Custom SLA
– 24*7 support
– Dedicated clusters
– Training
● Concurrent connection
– Free plan has 50 max connections, otherwise is
unlimited

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FAQ
● Enterprise solution
– Custom SLA
– 24*7 support
– Dedicated clusters
– Training
● Concurrent connection
– Free plan has 50 max connections, otherwise is
unlimited
● Lock-in

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FAQ
● Enterprise solution
– Custom SLA
– 24*7 support
– Dedicated clusters
– Training
● Concurrent connection
– Free plan has 50 max connections, otherwise is unlimited
● Lock-in
– Export data to JSON

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References
● Browser 與 Server 持續同步的作法介紹
● Comet (programming)
● Engine.IO: the realtime engine
● Engine.IO Protocol
● How Firebase Works
● Firebase Callbacks - what's the underlying trigger?
● Firebase under the hood - watching web sockets in
Chrome Developer Tools

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