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Actors and Threads
- 1. Actors and Threads Safer Concurrency for Ruby Mike Perham @mperham
- 2. Who Am I? •Numerous gems (dalli, memcache-client, rack-fiber_pool, connection_pool, etc) • Scalability/Performance guy • Fibers and EventMachine • Technical Lead at Carbon Five
- 3. Ruby History • Fun! •Implementation • Performance • Scalability
- 4. What This Isn’t •Threads vs Events vs Processes • Threads won’t make you love Java
- 5. Definitions • Concurrency -performing two operations in tandem (e.g. two web requests) • Parallelism - performing two operations literally at the same time (requires two cores) Concurrent Parallel
- 6.
- 7. The problem isalways communication (true in the real world too!)
- 8. Communication • Two fundamentalmechanisms • Share • Copy
- 10. IPC • Pipes • Sockets •Shared Memory • Files • POSIX 1988
- 11.
- 12. Threads • Much moreefficient than processes • Communication mechanism? • Variables! • POSIX 1995
- 13.
- 14.
- 15. End Goals • RuntimeEfficiency isn’t the only goal! • Remember Fun? • Ease of Development is huge
- 16. Locks • Hard toget right • Non-deterministic • Don’t scale
- 17.
- 18. Lock Benchmark # Results: Ruby 1.9.2, GIL means no parallel threading # user system total real # single locked 4.310000 0.010000 4.320000 ( 4.311850) # threaded locked 4.230000 0.080000 4.310000 ( 4.307405) # # Results: JRuby 1.6.3, parallel threads mean massive lock contention # user system total real # single locked 4.080000 0.000000 4.080000 ( 4.080000) # threaded locked 17.109000 0.000000 17.109000 ( 17.109000) Context Switching!
- 19.
- 20. What can wedo? • Look to other languages • Go • Scala • Erlang
- 21. Goroutines • Asynchronous function • You cannot get a handle to it • Send messages via a channel
- 22. Goroutines • Really likethis model • Maps well to a distributed model • Backed by a pool of threads
- 23. Actors • unit ofexecution • has a mailbox • You just send it a message, e.g. • actor << { :amount => 11.99 }
- 24. Actors • Thread- orFiber-backed • No application-level locks
- 25. Actor.rb • MRI/JRuby -no actors • Rubinius comes with actor.rb
- 26.
- 27. Actor.rb • Not idiomatic •Hard to understand, use correctly
- 28. Celluloid • Tony Arcieri(Revactor, Reia) • https://github.com/tarcieri/celluloid • OO Actors • Asynchronous method invocation • Mix of Threads and Fibers
- 29.
- 30. Celluloid Thoughts • Nice,idiomatic Ruby design • One object == one thread • Needs actor pooling
- 31. girl_friday • yours truly •http://github.com/mperham/girl_friday • Background processing pools • Parallel batch operations • More functional than OO • Thread-based
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- 33.
- 34. What if wedo need to share data?
- 35. I Love the80s!
- 36. I Love the00s!
- 37. STM • Software TransactionalMemory • All mutation via transactions • Provide ACI (not ACID) guarantees • See Clojure (and Cloby!)
- 38. Atomic Instructions • SincePentium (1993) • XCHG - swap registers or register/ memory • CPMXCHG - Compare And Set (‘CAS’)
- 39.
- 40. Atomic Benchmark # Results:JRuby 1.6.3 # user system total real # single atomic 2.041000 0.000000 2.041000 ( 2.041000) # threaded atomic 0.978000 0.000000 0.978000 ( 0.979000) 2 cores = 2x speedup!
- 41. Atomic Structures • java.util.concurrent • ConcurrentHashMap • ConcurrentLinkedQueue
- 42.
- 43. Concurrency It’s always hard! Modern languages should support tools and APIs that scale well AND are developer-friendly.
- 44. To Do • Needstandard Actor API • Concurrent data structures • STM impl for Ruby (via JRuby?) • Multiverse
- 45. Further Reading • Kilim- Actors for Java • Disruptor - concurrency without locks • Actors in Scala • Concurrency in Erlang
- 46. Thank You! Questions? @mperham http://mikeperham.com http://blog.carbonfive.com PS We’re hiring!