My talk session at RubyKaigi Takeout 2021, introducing Ractor and RightSpeed.

1. Ractor’s speed
is not light-speed.
Satoshi Tagomori (@tagomoris)

2. Satoshi Tagomori (@tagomoris)
a.k.a. Moris (モリス)
Freelance technical consultant (Aug 2021 ~)

4. Ractor
A new experimental feature
of Ruby 3.0
to run Ruby code in parallel on CPUs

5. Talks about Ractor in this Kaigi
• “Parallel testing with Ractors: putting CPUs to work”
by Vinicius Stock at Day 1
• “Ractor’s speed is not light-speed” (this talk)
by Satoshi Tagomori at Day 2
• “Ruby, Ractor, QUIC”
by Yusuke Nakamura at Day 3

6. Ractor’s Features
• Can run Ruby code of multiple Ractors in parallel on CPU cores
• by managing objects per Ractor
• Can move objects between Ractors
• Moved objects become invisible from the original Ractor
• Can share “shareable” objects between Ractors
• Modules, Classes
• Application code (Proc)
• De
fi
nitions (constants), Settings/Con
fi
gurations (frozen objects)
• …

7. What does “shareable” mean?
• Should be marked by Ractor.make_shareable(obj)
• will be frozen (in most cases)
• Proc: Ractor.make_shareable() makes Proc isolated
• “Isolated” Proc is not frozen, but shareable
• Proc#binding raises ArgumentError if it’s isolated
• All referred values (from the Proc) should be shareable too

8. Isolated Proc (1)

9. Isolated Proc (2)

10. Ractor:
The Feature for Speed

11. Question: How fast is Ruby w/ Ractor?
• xN faster if the laptop has N cpu cores?
• 8 cores on M1
• Is it true for Web applications?
• Is that faster than N processes by fork?
• Connection passing on memory (Ractor) vs RPC (fork)
• Does my webapp run faster w/ Ractor than the current deployment?

12. Needs: Experimental App Server using Ractor
• Rack application server
• Rack: protocol between server and application
• All servers are Rack server: webrick, unicorn, thin, puma, …
• Processing workers on Ractor
• Receive established connection, read request
• Run your Rack application
• Write response
• Speed: Appropriate performance, less overhead

13. light speed

14. light speed

15. right_speed
https:/
/github.com/tagomoris/right_speed
https:/
/rubygems.org/gems/right_speed

16. $ rackup -s right_speed config.ru
-O Host=127.0.0.1
-O Port=8080
-O Workers=12
Default # of workers is equal to # of CPUs

17. Demonstration
Running apps on right_speed
* Rack app
* Sinatra app
* Ruby on Rails app
https:/
/github.com/tagomoris/demo-webapps

18. Demonstration
Traffic
* single client connection + thread
* multiple client connections + threads

19. Problems about WebApps on Ractor
• SEGV at closing connections(?)
• Module/class instance variable accesses
• Accessing un-frozen (un-shareable) constants
• Dynamically de
fi
ned methods w/ un-shareable Proc

20. SEGV at closing connections (?)
• SEGV caused when it handles 2 (or more) connections
• bugs#18024

21. Module/Class Instance Variable Accesses
• Reading module/class instance variables causes Ractor::IsolationError
• Many frameworks (Rack, Sinatra, Rails) are heavily using it
• @var in the context of class << self
• for settings in many cases
• Used for default instance or default options (e.g., JSON.dump)
• Reading it will be allowed bugs#17592
• in the future (not
fi
xed yet)

22. Accessing Un-frozen/shareable Constants
• Constants can be accessible from Ractors, if deeply-frozen
• Use the magic comment always!
# frozen_string_literal: true
• Want a variant for Hash/Array (in my idea)
# frozen_shareable_constant_literal: true

23. define_method (1)
• Methods can be called in Ractor, usually
• Methods de
fi
ned by de
fi
ne_method may cause errors
• Blocks are unshareable!
• Frameworks (RoR/Sinatra/…) do this everywhere

24. define_method (2)
• Ractor-safe methods with shareable/isolated blocks
• Need shorthand!

25. Right Things to Be Done
• Applications: Check Ractor-safe or not
• Frameworks, libraries: Need many patches
• To make it Ractor-safe
• Ruby runtime: Make Ractor production ready
• More Ractor-safe core libraries
• More Ractor features (e.g, bugs#18139, etc)
• More features about productivity? (constant, proc, etc)

26. Thank you!