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RubyGems on ruby.wasm
Yuta Saito (@kateinoigakukun)
RubyKaigi 2024
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About me
• Yuta Saito / @kateinoigakukun
• Master's student at Waseda University
• Newbie commi>er of CRuby and SwiB
• Creator of ruby.wasm
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Overview
1. Introduc+on to ruby.wasm
2. Challenges of RubyGems support
3. Demo
4. Technical details
5. Future vision
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1. Introduc,on: ruby.wasm
• Introduced in RubyKaigi 2022
• Enables running Ruby on everywhere by WebAssembly
• This project consists of:
1. CRuby interpreter compiled to WebAssembly
2. Packaging system for interpreter + .rb files
3. JS interop library ( require 'js')
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require 'js'
button = JS.global[:document].createElement("button")
button[:textContent] = "Click me!"
button.addEventListener("click") do
puts "Hello~"
end
response = JS.global.fetch("https://example.com/data.json").await
puts response.json.await
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$ wasmtime run ruby.wasm hello.rb
Hello, world!
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But, what about RubyGems?
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2. Challenges of RubyGems support
RubyGems has two main components:
1. Installer: gem install
2. Run:me loader: require 'gem_name'
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2. Challenges of RubyGems support
Run$me loader
✅
• Supported from early versions
• require 'gem_name' works as expected
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2. Challenges of RubyGems support
Gem installer
!
When to install gems?
• On-the-fly installa/on
• Pre-installa/on
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2. Challenges of RubyGems support
On-the-fly installa.on
Install Gems at run-.me
• Convenient way for daily
scrip4ng
• Run gem install on
Wasm
• Requires network access at
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2. Challenges of RubyGems support
On-the-fly installa.on
• I showed on-the-fly installa2on demo at RubyKaigi 2022.
• Network access is passed through the browser's fetch API.
• You can try it now on runruby.dev by Svyatoslav
• No built-in support
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2. Challenges of RubyGems support
Pre-installa+on
Install Gems in advance before
running the Ruby program.
• No network access at Run-
1me
• "build" step before running
the Ruby program.
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Today's focus
Pure-Ruby Gems C-Extension Gems
On-the-fly
installa.on
⚠ ❌
Pre-installa.on ❌ ❌
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Today's focus
Pure-Ruby Gems C-Extension Gems
On-the-fly
installa.on
⚠ ❌
Pre-installa6on # #
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3. Demo: Mastodon in the browser
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h"ps:/
/mastodon-in-browser.vercel.app/boot.html
Mastodon in the browser Inspired by
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3. Demo - Mastodon in the browser
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Possible use case?
"Serverless Staging": Host Rails app as a sta3c site
• Low-cost
• Low security risk
• e.g. Preview environments for Pull Requests
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4. Technical details
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4. Technical details
1. Package Gems
2. Cross-compile C-Extensions
3. Pre-link C-Extension shared libraries
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4.1. Package Gems
Package gem source files into the WebAssembly binary by VFS
# WARNING: Still Experimental
$ bundle add ruby_wasm --group=development
$ bundle add rainbow
$ bundle exec rbwasm build -o ruby.wasm
(snip)
INFO: Packaging gem: rainbow-3.1.1
INFO: Size: 51.17 MB
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4.1. Package Gems
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4.2. Cross-compile C-Extensions
Cross-compila,on support in mkmf
• mkmf is the core of the C-extension build system in Ruby
• 3 major mkmf users (extconf.rb consumers in in other words):
• CRuby build system
• rake-compiler
• RubyGems
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4.2. Cross-compile C-Extensions
Cross-compila,on support status in major mkmf users
• CRuby build system & rake-compiler:
• Fake rbconfig.rb trick
• RubyGems:
"
• Does not support cross-compila
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4.2. Cross-compile C-Extensions
Exis%ng rbconfig.rb trick
• Overwrite top-level
RbConfig constants
• Does not work for some
corner cases
$ ruby -rrbconfig -rwasm32-wasi-fake extconf.rb
# ./rbconfig.rb
module RbConfig # For target platform
...
end
# ./wasm32-wasi-fake.rb
class Object
remove_const :CROSS_COMPILING if defined?(CROSS_COMPILING)
CROSS_COMPILING = RUBY_PLATFORM
constants.grep(/^RUBY_/) {|n| remove_const n}
RUBY_VERSION = "3.4.0"
RUBY_RELEASE_DATE = "2024-05-11"
RUBY_PLATFORM = "wasm32-wasi"
...
end
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# From https://github.com/rake-compiler/rake-compiler/blob/v1.2.7/lib/rake/extensiontask.rb
# Pre-load resolver library before faking, in order to avoid error
# "cannot load such file -- win32/resolv" when it is required later on.
# See also: https://github.com/tjschuck/rake-compiler-dev-box/issues/5
require 'resolv'
require 'rbconfig'
...
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4.2. Cross-compile C-Extensions
Cross-compila,on support without trick
✅
Feature #20345: Add --target-rbconfig op3on to mkmf2
h9ps:/
/bugs.ruby-lang.org/issues/20345
$ ruby extconf.rb --target-rbconfig=path/to/rbconfig.rb
creating Makefile
$ make
$ file nokogiri.so
nokogiri.so: WebAssembly (wasm) binary module version 0x1 (MVP)
2 Will be available in Ruby 3.4 and later
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4.2. Cross-compile C-Extensions
Cross-compila,on support in RubyGems
!
PR #7628: Add --target-rbconfig op.on to gem install
h"ps:/
/github.com/rubygems/rubygems/pull/7628
$ gem install nokogiri --target-rbconfig=path/to/rbconfig.rb
$ bundle install --target-rbconfig=path/to/rbconfig.rb
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4.3. Pre-link C-Extension shared libraries
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4.3. Pre-link C-Extension shared libraries
Why not sta*c linking?
• We already support sta/cally-linked C-extensions
• But, the build model is not suitable for the RubyGems ecosystem
• Take a long linking /me (especially due to Asyncify)
• Need to /ghtly integrate with the CRuby build system
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Sta$c linking Dynamic linking
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4.3. Pre-link C-Extension shared libraries
Why not dynamic linking so far?
• WebAssembly does not have a standard dynamic linking ABI
• If we do our bespoke dynamic linking3, the binary will be
incompa?ble with standard WebAssembly run?mes
3 Emscripten does dynamic linking by its own loader
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4.3. Pre-link C-Extension shared libraries
Breakthrough: Component Model
• A new layer of WebAssembly standard
• Consists of:
• WIT (WebAssembly Interface Types) IDL
• Module linking
• ... and more
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4.3. Pre-link C-Extension shared libraries
Module Linking
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4.3. Pre-link C-Extension shared libraries
Dynamic Linking upon Component Model
• Each module has its metadata for dynamic linking
• "AOT" linker encapsulates "how to link modules" into
Component
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4.3. Pre-link C-Extension shared libraries
AOT dynamic linking
A new concept of dynamic linking in WebAssembly
• Done at the build /me
• The final binary is a Component
• The linker is originally developed by Joel Dice in wit-component
• Adjusted for Ruby use case
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4.3. Pre-link C-Extension shared libraries
Difference from the tradi0onal dynamic linking
• The final binary, a Component, contains all the dependencies
• No file-based shared library search at run:me
• dlopen is available only for libraries known at build-:me
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Current status
Pure-Ruby Gems C-Extension Gems
On-the-fly
installa.on
⚠ ❌
Pre-installa6on ✅ ✅ (soon)
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5. Future vision
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Roadmap
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Interpreter size
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Summary
• RubyGems support will be available soon on ruby.wasm
• Ruby is leveraging the state-of-the-art WebAssembly technology
including the Component Model
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Acknowledgements
• Supported by the Ruby Associa4on Grant Program
• Advised by @mame and @ko1
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