The 7th Annual IndicThreads Pune Conference was held on 14-15 December 2012. http://pune12.indicthreads.com/

1. Typesafe Stack Software
Development On The JVM
Sushanta Pradhan
Talentica Software (I) Pvt. Ltd.

2. History of Hardware Architecture
• Single core era
• moore's law achieved by increasing clock cycles
• Multi core era
• moore's law achieved by increasing # of cores

3. Moore’s Law

4. PPP – Grand Challenge
• Parallel programming as easy as sequential
programming
• Moores’s law of performance – speed up 2 times year
on year
• Eliminate concurrency bugs

5. History of software applications
• pre .com era
• standalone desktop apps
• .com era
• web sites - static web pages, automated business
processes
• data controlled by software vendor
• deployed on data centers

6. contd ..
• web2.0/semantic web era
• web/networked applications
• Smart apps
• data not controlled by vendor but by the users
• deployed on cloud

7. Properties of modern day App
• Scalability
• Distributed
• Parallel & Concurrent
• Dynamic
• Agile & Swift

8. Parallelism & Concurrency
• Parallel Programming
• parallel execution of programs
• can't be performed without parallel hardware
• programs get faster

9. Parallelism & Concurrency
• Concurrent Programming
• simultaneous execution of programs
• can be performed without parallel hardware
• programs get more responsive
Both are too hard !!

10. Why Hard?
• non-determinism due to shared mutable state by
concurrent threads
• encapsulate state in actors or transactors but fundamental
problems still remains
non-determinism = parallel processing + mutable state

11. Remedy?
PREVENTION IS BETTER THAN CURE !!
• Avoid mutable state and get deterministic processing
• Which means program functionally

12. Space vs Time
Space(functional/parallel)
Time(imperative/concurrent)

13. Scala
• Hybrid – functional & object oriented (pure)
• strong static typing
• Agile - concise & expressive
• Parallel & Sequential
• intermixes well with Java

14. Scala contd ..
Parallellism
• parallel collections
• distributed collections
Concurrency
• Actors
• STM Akka
• Futures

15. Scala contd ..
• Concise Java
• Immutability Val & Var
• Tuples & Multiple Assignments
• Sensible Defaults
• Operator Overloading

16. Scala classes ..
• Terse
• Object keyword - Singleton
• Companion Objects
• Type inference
• Option[T] – Some[T], None

17. Class hierarchy

18. Scala – Functional Aspects
• Functions too are objects
• Higher Order Functions
• Partially applied Functions
• Closures

19. Scala Inehritance
• Traits
• Mixins
• Type inference - implicit keyword

20. Scala collections
• Mutable & immutable
• filter()
• Map()
• foldLeft()
• foldRight()

21. Scala – Pattern Matching
• Advanced switch case
• Literals and constants
• WildCards
• Tuples & Lists
• Guards
• Regular Expressions

22. Scala - Concurrency
• actor()
• Actor Class
• receive() & recieveWithin()
• react() & reachWithin()
• loop() & loopwhile()

23. Akka - Middleware
• Concurrent, Scalable & fault-tolerant
• based on actor model
• highly performant
• event driven
• location transparency

24. Actor system
• ensemble of actors sharing common configuration
• hierarchical structure
• heavyweight
• has its own pool of resources threads

25. Supervision
• dependency relationship between actors
• supervisor - subordinate model
• supervisor monitors and reacts to any errors reported
by subordinates
• configurable supervision strategy
• lifecycle monitoring

26. Supervision hierarchy
”root guardian”
”guardian”
shutdown “system
guardian”
order

27. Remoting
• ActorPath
• purely local - "akka://my-sys/user/service-a/worker1"
• local or remote - "akka://my-sys@host.example.com:5678
/user/service-b"
• Seamlessly send messages to actors on remote nodes

28. Routing
• route messages to actors(routees)
• ideal for load balancing
• Examples
• RoundRobinRouter
• RandomRouter
• SmallestMailboxRouter
• BroadcastRouter

29. Dispatchers
• make akka actors tick
• manages the resources(threads) used by actors
• configure mailboxes of actors
• Examples
• fork-join-executor
• thread-pool-executor

30. Play
• ruby on rails like agility
• convention over configuration
• seamless integration with akka for scalability
• edit and test

31. Play contd ..
• an easy, out-of-the-box setup for unit and functional testing
• asynchronous HTTP request handling
• WebSocket support
• cache support (e.g. memcached)
• integrated JSON and XML handling

32. Progressive Stream Processing
• Iteratees
• Enumerators
• Enumeratees

33. Q/A