Replicated Service Objects -- A Strategy for Distributed Applications Video: https://youtu.be/_MtwXqYsBD0 Fri, August 26, 11:00am – 11:45am First Name: Martin Last Name: McClure Email: martin.mcclure@gemtalksystems.com Title: Replicated Service Objects -- A Strategy for Distributed Applications Type: Talk Abstract: Early in the history of distributed Smalltalk applications, designers built systems that provided transparent distribution. This enabled distributed applications to be written almost as if they were on a single machine. After the explosion of the Internet in the late '90s, it was widely recognized that this approach led to applications that did not perform well -- application developers needed to be aware of and design around communication latency. One solution to this problem is Replicated Service Objects, an architecture for distributed Smalltalk applications that makes it easy to minimize the impact of network latency. Bio: Martin has been interested in Smalltalk since he first heard about it in 1975. After a frustrating ten-year wait he finally got his hands on a running Smalltalk system and hasn't let go since. As a senior engineer working on GemStone Smalltalk products at GemTalk Systems, he leads a team that designs and implements a distributed object system that acts as a bridge between a Smalltalk client and a GemStone Smalltalk server. In his spare time, he works on Mist (a Smalltalk-like language with improved modularity and security and no virtual machine) and does a lot of contra dancing. Lately, he's been working on remodeling an old house with attached former church which will become his home with built-in dance hall.

1. Martin is getting the
projector
to work
with his
laptop.

2. Replicated
Service Objects
A Strategy for
Distributed
Applications
Martin McClure

3. Background:
GemStone/S

4. 30 Years!

6. GemStone/S
•Server-side Smalltalk
•Object Database

7. Server-side
Smalltalk
•Headless
•Multi-User
•Scalable

8. Object
Database
•One persistent “image”
•Shared transactionally
• Merged at commit
• Conflicts are detected

9. GemBuilder for
Smalltalk (GBS)
•Interfaces VW or VA
Smalltalk to GemStone

12. GemBuilder for
Smalltalk (GBS)
•Interfaces VW or VA
Smalltalk to GemStone

13. GBS Main Features
•Forwarders
• Remote messaging
•Replicates
• Synchronized copy
• (new) Remote
messaging

14. Forwarder
Server
Client

15. Forwarder
Server
Client

16. Forwarder
Server
Client

17. Forwarder
Server
Client

18. Replicate
Server
Client

19. Replicate
Server
Client

20. Replicate
Server
Client

21. Replicate
Server
Client

22. Replicate
Server
Client

23. Replicate
Server
Client

24. Replicate
Server
Client

25. Replicate
Server
Client

26. Replicate
Server
Client

27. Replicate
Server
Client

28. Transparent
Distribution

29. Transparent
Distribution
Good Idea

30. Transparent
Distribution
Good Idea
BAD

31. Distribution
Concerns
•Correctness
•Reliability
•Performance

32. Distribution
Concerns
•Correctness
•Reliability
•Performance


33. Distribution
Concerns
•Correctness
•Reliability
•Performance



34. Distribution
Concerns
•Correctness
•Reliability
•Performance




35. An
Embarrassing
Story

36. n2

37. One
Month

38. Tools used
Forwarders

39. Lessons
•Test scaling
•Test with latency
•Need better design
pattern

40. Replicated
Service
Objects

41. Example:
Inspector
Service

42. Server
Client

43. Server
Client
Inspector
Service
theObject
properties

44. Server
Client
Inspector
Service
theObject
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary

45. Server
Client
Inspector
Service
theObject
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary

46. Server
Client
Inspector
Service
theObject
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary

47. Server
Client
Inspector
Service
theObject
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary

48. Server
Client
Inspector
Service
theObject
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary

49. Server
Client
Inspector
Service
theObject
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'
Dictionary

50. Server
Client
Inspector
Service
theObject
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> '0'
'y' -> '0'
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'
Dictionary

51. Server
Client
Inspector
Service
theObject
properties
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'
Dictionary
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'

52. Server
Client
Inspector
Service
theObject
properties
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'
Dictionary
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'

53. Server
Client
Inspector
Service
theObject
properties
Dictionary
Inspector
Service
properties
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'
Dictionary
'self' -> '0@0'
'class' -> 'Point'
'x' -> ' 42 '
'y' -> '0'

54. Principles
•Replicate everything
you'll need frequently

55. Principles
•Represent information
as basic objects when
necessary.

56. Principles
•Do everything you can
predict in a single round
trip.

57. Replicated
Service Objects
A Strategy for
Distributed
Applications
Martin McClure