Nick Sieger JRuby Concurrency EMRubyConf 2011
1 like762 views
This document discusses concurrency in JRuby and presents several approaches for managing concurrent operations, including Java's java.util.concurrent utilities, Jetlang fibers and channels, and the Akka actor framework. It notes some challenges with using green threads in JRuby due to shared mutable state and provides examples demonstrating thread safety issues and solutions using these other concurrency models.
![data = []
M.times do |m|
Thread.new do
N.times do |n|
data << m * n
end
end
end](https://image.slidesharecdn.com/nick-sieger-emrubyconf-2011-110519155704-phpapp02/85/Nick-Sieger-JRuby-Concurrency-EMRubyConf-2011-10-320.jpg)
![class WorkerTask
def run
@thread = Thread.new do
50.times do
digest = Digest::MD5.new
@range.step(1024) do |idx|
digest.update(@data[idx...idx+1024])
end
end
end
end
end](https://image.slidesharecdn.com/nick-sieger-emrubyconf-2011-110519155704-phpapp02/85/Nick-Sieger-JRuby-Concurrency-EMRubyConf-2011-12-320.jpg)
Nick Sieger JRuby Concurrency EMRubyConf 2011
- 1. JRuby Concurrency Nick Sieger EMRubyConf @ RailsConf 2011
- 2. Mental Model http://www.flickr.com/photos/solar_decathlon/4524503892/
- 4. Uncertainty /* ruby/struct.c */ static VALUE rb_struct_equal(VALUE s, VALUE s2) { /* ... */ if (RSTRUCT_LEN(s) != RSTRUCT_LEN(s2)) { rb_bug("inconsistent struct"); /* should never happen */ } /* ... */ } O RLY?!
- 5. How could this code fail? class ExpensiveToCreate def self.instance @instance ||= ExpensiveToCreate.new end end
- 6. How could this code fail? class ExpensiveToCreate def self.instance unless defined?(@instance) @instance = ExpensiveToCreate.new end end end
- 7. How could this code fail? class ExpensiveToCreate def self.instance T2 unless defined?(@instance) @instance = ExpensiveToCreate.allocate T1 @instance.initialize # big pause here @instance end end end
- 8. Avoid shared mutable state, lazy initialization MutableConstant.merge! :key => value class MemoryCache def self.cache @cache ||= {} $global_lock.do_something! end end
- 9. Difficult to observe with green threads
- 10. data = [] M.times do |m| Thread.new do N.times do |n| data << m * n end end end
- 11. OK NOT OK instance vars method def String class def Array class vars Hash
- 12. class WorkerTask def run @thread = Thread.new do 50.times do digest = Digest::MD5.new @range.step(1024) do |idx| digest.update(@data[idx...idx+1024]) end end end end end
- 13. Other Concurrency Approaches
- 15. require 'java' java_import java.util.concurrent.Executors @count = java.util.concurrent.atomic.AtomicInteger.new def send_email(executor) executor.submit do puts "email #{@count.incrementAndGet} sent" end end
- 16. executor = Executors.newCachedThreadPool send_email(executor) executor = Executors.newFixedThreadPool(2) loop do send_email(executor) end
- 18. require 'jretlang' fiber = JRL::Fiber.new channel = JRL::Channel.new fiber.start channel.subscribe_on_fiber(fiber) do |msg| puts msg end channel.publish "Hello"
- 19. Akka http://akka.io http://j.mp/jruby-akka
- 20. require 'akka' class HelloWord def hi puts "hello actor world" end end Actors.actorOf(HelloWord.new).hi puts "initiating shutdown..." Actors.delayedShutdown 1