more choices for java's default share-state concurrency model the doc is incomplete

1. More Than Java
Concurrency
Darren.Wang( 强)
Thursday, January 20, 2011

2. Agenda
More Than Java Concurrency? What’s More?
Several Concurrency Models/Patterns
Case Study
Questions?
The end
Thursday, January 20, 2011

3. Why concurrency?
Thursday, January 20, 2011

4. What concurrency
offers
reduce latency
divide and conquer, run in parallel reduce
the latency
hide latency
asynchronous
increase throughput
more tasks can be run without wasting
available computing power
Thursday, January 20, 2011

5. What we do with
Java Concurrency
State , That’s all of the about.
Atomicity - keep state intact
Visibility - make right state access
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6. When Things Go
Wrong
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7. What If ...
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8. What We Will Talk
Today
Share-State Concurrency
Share-Nothing Concurrency
Software Transaction Memory
Data-Flow Concurrency
Thursday, January 20, 2011

9. Share-State
Concurrency
Thursday, January 20, 2011

10. JMM Simplified
Picture borrowed from <<Java >>
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11. JMM escalation
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12. How to deal with?
How many ways can you count?
Here we go...
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13. Immutability
immutable anytime
Immutable Object
immutable before publishing
Map & ConcurrencyMap
(1)To Find More in book <<Java Concurrency In Practice>>
Thursday, January 20, 2011

14. Confinement
Thread Confinement
Thread-Specific Variables(ThreadLocal)
Stack Confinement
Method Stack Scope
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15. Synchronization
Synchronized Block(Implicit Lock)
Explicit Lock
Volatile (Partial Synchronization Support)
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16. Gotchas With
Synchronization
Deadlock
how to prevent it?
Live lock
Starvation
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17. Gotchas With
Synchronization
Deadlock
how to prevent it?
Resource Re-ordering
Live lock
Starvation
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18. Gotchas With
Synchronization
Deadlock
how to prevent it?
Resource Re-ordering
Periodic Retry
Live lock
Starvation
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19. Performance Tuning
with Synchronization
reduce the time of holding locks
break global locks into fine-grained locks
what coming next?
Thursday, January 20, 2011

20. CAS
Compare-And-Set | Compare-And-Swap
java.util.concurrent.atomic after Java5
AtomicInteger
AtomicLong
AtomicBoolean
AtomicReference
Thursday, January 20, 2011

21. Section Conclusion
Pessimistic Model
Lock-Based
Optimistic Model
Lock-Free
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22. Share-Nothing
Concurrency
Thursday, January 20, 2011

23. Share-Nothing
Concurrency
AKA. Message Passing Concurrency
Confinement In a Big Picture
Thursday, January 20, 2011

24. Actor Model
First proposed by Carl Hewitt in 1973
improved by Gul Agha
An Actor Can:
change internal state
send messages to peer actors
create new actors
migrate to another computing host
Thursday, January 20, 2011

25. Actor Rocks
more light weight
event based actors of akka can create
6.5million on 4 G RAM (600 bytes each)
much easier, just send messages
counter ! tick
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26. Actors Available
Erlang Platform
Scala Platform
TBA, EBA
Lift Actor, Akka Actor
Java Platform
Kilim, SALSA(simple actor language, system
and architecture)
Other
Thursday, January 20, 2011

27. Actor Almighty?
when we really have shared states, e.g. bank
account?
when we need to form unified consensus
when we need synchronous behavior
a bit verbose compared to method dispatch
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28. Section Conclusion
Actor Model Rocks In Some Situations, But not
all
Share Nothing Simplify the Architecture Design
Prefer Share Nothing to Share State If Possible
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29. You Know Lego,
Right?
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30. Case Study I
Session Management
Centralized Storage
memcached, database...
Client-Specific Storage
secure cookie
other local-storage mechanism
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31. Case Study II
Map-Reduce
When Share Nothing can rock in
When Share State Is a Must
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32. Case Study III
Symmetric Cluster
Share Nothing
Asymmetric Cluster
Share State
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33. STM
Software Transaction Memory
Transaction operations execute in the own
thread in parallel, commit will cause One to be
successful and others to abort or retry
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34. Sounds Familiar?
Optimistic Model
Can be nested
Simple Programming Model
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35. Available Solutions
Clojure
Concurrent Haskell
STM .Net
More...
Thursday, January 20, 2011

36. Cons
All operations in scope of a transaction:
need to be idempotent
can’t have side-effects
Memory Concern
Conflicting Rate Concern
Thursday, January 20, 2011

37. Section Conclusion
optimistic model
simple programming model
with restrictions
which may cause limitations(MS drops STM)
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38. Data-Flow
Concurrency
AKA. Declarative Concurrency
Thursday, January 20, 2011

39. Have you ever...
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40. Features
Single Assignment Variables
Data-States trigger process flow
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41. Available
Languages
LabView
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42. Usage Scenarios
Signal Process System
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43. Typical Operations
create a data-flow variable
wait for the variable to be bound
bind the variable
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44. Limitations
Can’t have side-effects
Exceptions
IO
Others
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45. Section Conclusion
Data Based Concurrency
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46. comparison of
common facilities
Executor (Agent)
Actor (HawtDispatch)
STM
Transactor(Actor + STM)
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47. Thursday, January 20, 2011

48. Thank You
Thursday, January 20, 2011

49. The End
Thursday, January 20, 2011