Fiber and Em-synchrony @ShiningRay

Fiber Fibers are primitives for implementing light weight cooperative concurrency in Ruby. Add to Ruby core in 1.9

Fiber == Coroutine

Fiber vs Thread vs Process ● Process simulates CPU and Memory, Preemptive ● Thread simulates CPU, Preemptive ● Fiber: none, cooperative, manually schedule

Coroutine vs Routine ● Routine: return only once ● Coroutine: can return(yield) multiple times

Benefit of Fibers ● Small & lightweight: much smaller than thread/process, so we can spawn more. ● Can be schedule only when necessary, reduced context-switch, lighten the burden of CPU. ● So can handle higher concurrency than per- thread or per-process mode.

PS: Coroutines can be implemented by call/cc.

Warning: Fiber can also lead to concurrent problem like race condition.

Em-Synchrony = Fiber + EventMachine

Em-Synchrony: Good Parts ● High Concurrency of evented model ● Ease of sequential programming, no pain of callbacks https://github.com/igrigorik/em-synchrony

Basic Idea ● Untangling Evented Code with Ruby Fibers ● http://www.igvita.com/2010/03/22/untangling-eve nted-code-with-ruby-fibers/

Basic Idea ● Use Fiber to save the context after sending a asynchronous request. ● Switch back to parent Fiber(for scheduling other fibers) ● Resume the saved Fiber after asynchonous request completes.

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More ● Fiber aware ConnectionPool with sync/async query support ● Fiber aware Iterator to allow concurrency control & mixing of sync / async ● Fiber aware async inline support: turns any async function into sync ● Fiber aware Multi-request interface for any callback enabled clients ● Fiber aware TCPSocket replacement, powered by EventMachine ● Fiber aware Thread, Mutex, ConditionVariable clases ● Fiber aware sleep, defer, system

High-concurrency Framework using em-synchrony ● Goliath ● Sinatra-synchrony

Em-Synchrony: The Bad Parts ● You must use a customized fiber aware driver for asynchronous tasks. (em-mysql em-redis ...)

Suitable for Web Service APIs

Asynchronous Rails

You need ● Em-synchrony ● Rack-fiber_pool ● Config.threadsafe! ● Thin(evented server) ● Fiber aware driver for (db/http/service) connections

Gemfile

Config.ru

Application.rb

Database.yml

Use Ruby 2.0 Ruby 1.9 4k Fiber stack size. Too small to fit common Rails app. Ruby 2.0 has 200k default Fiber stack size. And you can change it via:

Thank you