A Whole New World: Rails on the JVM with JRuby!

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A Whole New World! Rails on the JVM with JRuby!

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Who Am I • Charles Oliver Nutter • @headius(@mastodon.social) • [email protected] • JRuby developer since 2004 • Full-time JRuby and JVM language advocate since 2006

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What is JRuby? • An implementation of Ruby atop the Java Virtual Machine • Ruby implementation fi rst, JVM language second • Many bene fi ts from JVM ecosystem • Ruby code should "just work" • Different extension API, no forking, parallel threads • www.jruby.org

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Ruby Compatibility • JRuby 9.4 is out now! • Ruby 3.1 compatible, 98% of language specs passing • Nearly complete core + stdlib features from 2.7, 3.0 and 3.1 • JRuby 9.3 (Ruby 2.6 compat) • Maintenance through 2023 as needed • Compatibility before performance! • Now we can refocus on optimization again

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Ruby 3.2 Coming Soon! • Checklist issue: jruby/jruby#7517 • You can help us add missing features! • Hopefully release 3.2 compatibility in the next 6 months

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Why JRuby? • JVM GC, JIT, concurrency scales Rails extremely well • Rich tools for monitoring, pro fi ling, debugging • Wide platform support: desktop, server, mobile • Zero-compile cross-platform GUI support • Java ecosystem moving fast, with thousands of excellent libraries

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Getting Started

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JRuby Install • Install a JDK • Java 11+ recommended, there's many distributions out there • Java 8 supported for 9.4 and lower • Install JRuby • Recommended: system package, Ruby installer, Docker image • Download tarball/zip or Windows installer

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Test it out! [] ~ $ rvm use jruby Using /Users/headius/.rvm/gems/jruby-9.4.2.0 [] ~ $ irb >> runtime = java.lang.Runtime.runtime => # >> runtime.available_processors => 8 >> runtime.free_memory => 91420584 >>

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JRuby on Rails

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JRuby Runs Rails! • Since 2007! • "Are there JRuby users running Rails applications?" • Oh yes! And at large scale! • Bene fi t from the JVM, libraries, languages • Great way to scale large Rails apps today!

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Rails 7 • Rails 7 works on JRuby 9.4! • activerecord-jdbc for JRuby: SQLite, MySQL, PostgreSQL • Version 60.0 for Rails 6, 70.0 for Rails 7, etc • Oracle, SQL Server, DB2, are available, may need updates • Performance and compatibility looking good!

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Rails 7 actioncable: 203 runs, 921 assertions, 0 failures, 10 errors actionmailbox: 92 runs, 238 assertions, 0 failures, 0 errors actionmailer: 230 runs, 516 assertions, 0 failures, 1 errors actionpack: 3550 runs, 16802 assertions, 1 failures, 1 errors actiontext: 80 runs, 145 assertions, 7 failures, 2 errors actionview: 2424 runs, 5395 assertions, 2 failures, 4 errors activejob: 368 runs, 837 assertions, 0 failures, 0 errors activemodel: 966 runs, 2853 assertions, 5 failures, 0 errors activestorage: 392 runs, 1121 assertions, 0 failures, 0 errors activesupport: 5188 runs, 12926 assertions, 43 failures, 28 errors 99% passing!

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Minimal Con fi g Changes • Generate a new app, Rails will use JRuby defaults • Use threads in Puma instead of workers • 2n+1 is a good rule of thumb • Make sure to increase DB connections as well • Existing app: try bundling, replace unsupported libs • Let us know! We can prioritize adding JRuby support!

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Scaling Rails with JRuby

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Scaling Rails • Classic problem on CRuby/MRI • No concurrent threads, so we need worker processes • Processes duplicate runtime state and waste resources • JRuby is the answer! • Multi-threaded single process runs your entire site • Single process with leading-edge GC uses resources better

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Baseline Rails App • Scaffolded "blog" application on PostgreSQL, Puma • IBM VPC instance: 8 vCPU, 32GB • CRuby 3.2, 16 workers • JRuby 9.4: 16 threads • Database, siege benchmark driver on same instance

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Workers vs Threads • Workers duplicate a lot of work • N * GC overhead, single large heap is better • N * JIT overhead and memory usage • Unavoidable to have some duplicated memory • JVM and JRuby support real parallel threads • One process, one GC, one JIT scales all the way up

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Caveats • PostgreSQL local via Docker (<5% overhead) • Siege benchmark driver also local (<5% overhead) • Very minimal blog app, full end-to-end requests • JRuby tuning and warmup time are important

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Requests per second 0 450 900 1350 1800 60s siege iteration 1 2 3 4 5 6 7 JRuby 9.4 CRuby 3.2

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requests per second (higher is better) 0rps 450rps 900rps 1350rps 1800rps 1,280rps 1,705rps JRuby 9.4 CRuby 3.2

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Memory • Baseline • JRuby: 3.4GB RSS • CRuby: 16x 103MB = 1.6GB • With tuning options • JRuby with 300MB heap: 955MB • CRuby YJIT: 16x 125MB = 2GB

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Requests per second 0 450 900 1350 1800 60s siege iteration 1 2 3 4 5 6 7 JRuby CRuby 3.2 JRuby 300MB heap CRuby 3.2 + YJIT

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requests per second (higher is better) 0rps 450rps 900rps 1350rps 1800rps 1,550rps 1,643rps 1,280rps 1,705rps JRuby 9.4 CRuby 3.2 JRuby 300MB heap CRuby + YJIT

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JRuby on Rails Scales! • More requests per second with lower latency • Lower memory usage beyond 8-10 concurrent users • Deploy anywhere that has a JVM (which is basically everywhere) • Leverage JVM tools to monitor and optimize

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True Story • Large Rails application using 40 xlarge on EC2 • 40 worker processes per server • 100k-150k req/min, 50-75ms response times • Migrated app to JRuby, made more use of threading • Down to 10 xlarge, 75% cost reduction • Consistently over 150k req/min, 30ms response times $

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Deploying JRuby the Ruby Way • Typical servers, devops tools in Ruby work fi ne • Usually no compilation required; install and go • Scales great with Puma • Rails using Puma by default • Small frameworks (e.g. Sinatra, Roda) scale even better

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Deploying with Warbler • gem install warbler ; warble • Bundle your app + libs + JRuby into a single fi le • Hand off to ops to deploy or run as executable (w/ built-in server) • One click deploy to Java clouds: • Elastic Beanstalk, Google AppEngine, etc • github.com/jruby/warbler

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But wait, there's more!

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So much more! • JVM and JRuby have much more to offer • We'll cover a few areas that make JRuby stand out • Some of these are early or experimental, but very exciting!

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JVM Tools

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JDK Flight Recorder • Low-overhead monitoring and pro fi ling for JVM • Always-on monitoring <1% overhead • Active pro fi ling around 5% overhead • Track memory, heap usage, GC, hot methods, JIT activity • Think New Relic, AppSignal, Sentry.io... but built-in and FREE

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JDK Mission Control • GUI control center and visualizer for Flight Recorder data • Start and manage recordings • Save, load, and browse recorded data • https://adoptium.net/jmc/

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Visual VM

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GUI and Graphics

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GUI Libraries • Swing, built into JDK • Clean, cross-platform, easy to build simple UIs • Scalable Windowing Toolkit (Eclipse SWT) • Native widgets, WebKit browser component, rich ecosystem • JavaFX (via JRubyFX, github/jruby/jrubyfx) • Scene-based, vector drawing, event-driven modern UI library

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Shoes 4

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Glimmer • Glimmer GUI DSL • Multiple backends (SWT, GTK, ...) • JRuby + SWT is the most mature • JRuby makes cross-platform GUI much easier! • Works same everywhere • GUI libraries shipped with gem

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Purugin for Minecraft event(:player_egg_throw) do |e| e.hatching = true e.num_hatches = 120 e.player.mesg "hatched" end

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GUIs... like Android?

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Ruboto: JRuby on Android • ruboto.org • Actively used for commercial projects today • Build interface with GUI builder, wire it up with Ruby code • Neglected a bit but being updated for JRuby 9.4 now!

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Trying Ruboto IRB • Original was pulled from store because it asked for ALL privileges! • Duh, it was a tech demo and REPL • We will republish soon, but search for two packages to download: • Ruboto Core: JRuby and Ruboto framework as a shared package • Ruboto IRB: REPL, editor, example scripts

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More JVM Features for Ruby

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InvokeDynamic

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InvokeDynamic • User-de fi ned binding of methods and values • Language decides target based on dynamic lookup logic • JVM optimizes that target like static code • Introduced in Java 1.7 (2011) with input from JRuby • Key to JRuby performance!

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InvokeDynamic Performance Times faster than JRuby Java 8 no indy 0 1.25 2.5 3.75 5 Mandelbrot Red/Black 4.05x 3.92x 3.74x 3.68x 3.72x 1.97x Java 8 indy Java 11 indy Java 17 indy 3.28x CRuby JIT 1.86x CRuby JIT

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Indy + Graal JIT? Times faster than JRuby Java 8 no indy 0 4 8 12 16 Mandelbrot Red/Black 3.13x 15.7x 4.05x 3.92x 3.74x 3.68x 3.72x 1.97x Java 8 indy Java 11 indy Java 17 indy Graal CE indy Escape analysis But not always better

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Project Loom

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Project Loom • JRuby's fi bers are based on threads • Too many, JVM blows up! • Scheduling, resource-intensive • Loom brings fi bers to JVM • Easily handles thousands of fi bers • Faster context-switching

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5.times do t = Time.now # create 100k fibers ary = 100_000.times.map { Fiber.new { } } # resume and complete 100k fibers ary.each(&:resume) p Time.now - t end

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$ jruby fiber_test.rb [7.603s][warning][os,thread] Attempt to protect stack guard pages failed (0x00007fc240a00000-0x00007fc240a04000). # # A fatal error has been detected by the Java Runtime Environment: # Native memory allocation (mprotect) failed to protect 16384 bytes for # memory to guard stack pages # # An error report file with more information is saved as: # /home/headius/work/jruby93/hs_err_pid75149.log # # If you would like to submit a bug report, please visit: # https://bugreport.java.com/bugreport/crash.jsp # Aborted (core dumped) 😩

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--enable-preview

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$ jruby -J--enable-preview fiber_test.rb 2.324123 0.880373 0.6916289999999999 0.73703 0.655856 🤩

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Project Panama • Foreign function interface (FFI) • With JVM help to make direct calls • Foreign memory API • JVM-assisted access, lifecycle • API extraction from C/++ headers • Save time setting up bindings

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jextract code generator • Writing bindings using FFI or Fiddle is still challenging • Parameter sizes, struct layout, in and out values, pointers • Differences across platforms • jextract: produce Panama/FFI stub code from a C header fi le • Call that stub code from JRuby... easy FFI for all!

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Wrapping Up

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JRuby Future • JRuby 9.4 continues to stablize • Many production users already! • Big optimization work coming the rest of this year • JRuby 9.5: Java 17 minimum, Ruby 3.2 support, many optimizations • Lots of new JVM features to leverage • Looking into native compilation, snapshotting for fast startup!

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JRuby on Rails Future • Rails 7 support is looking great! • We are caught up again, will keep tracking updates • As your app grows, JRuby can help you scale • Reduce resources, save money 🤑 • Let's talk about running your app on JRuby!

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Thank You! • Charles Oliver Nutter • [email protected] • @headius • https://github.com/jruby/jruby • https://www.jruby.org