JRuby on Rails: From Zero to Scale

JRuby is deployed by hundreds of companies around the world, running Rails and other services at higher speeds and with better scalability than any other runtime. With JRuby you get better utilization of system resources, the performance and tooling of the JVM, and a massive collection of libraries to add to your toolbox, all without leaving Ruby behind.

In this talk, we'll walk you through the early stages of using JRuby, whether for a new app or a migration from CRuby. We will show how to deploy your JRuby app using various services. We'll cover the basics of troubleshooting performance and configuring your system for concurrency. By the end of this talk, you’ll have the knowledge you need to save money and time by building on JRuby.

(This talk was delivered at RailsConf 2019)

Transcript

1. JRuby: From Zero To Scale
   Charles Oliver Nutter (@headius)
   Thomas Enebo (@tom_enebo)
   

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2. • JRuby co-leads
   • Red Hat Inc.
   Charles Thomas Ruby
   Java
   Beer
   

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3. #FreeOlaBini
   • Ola Bini, former JRuby contributor,
   is being held without cause by
   Ecuadorian authorities in connection
   with Julian Assange
   • His detention is illegal and should
   worry all of us
   • Please tell your friends about Ola
   and support efforts to help force the
   Ecuadorian authorities to release
   him
   

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5. Ruby Implementation First!
   • As compatible as we can be
   • All your Ruby code should just work*
   • * - except a few things we cannot support like fork()
   • No native c extensions (but we have java extensions)
   • Please report any problems
   

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6. JVM Language
   Gets all the benefits the Java platform has to offer...
   

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7. JVM Tools and GC
   

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8. Parallel and Concurrent
   

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9. Access to JVM Libraries
   Everything which has ever been made also has a JVM library for it
   

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10. Roadmap
    • 9.2.7.0 last week, 9.2.8.0 in May
    • 9.1.x is EOL
    • How to handle 2.6?
    9.1.17.0
    ...
    9.2.0.0
    2.5.3+
    2.3.x
    2.6?
    9.2.7.0
    master
    jruby-9_1
    9.1.1.18.0 EOL
    ruby-2.6
    

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11. Skip 2.6 Support?
    • JRuby 9.3 -> Ruby 2.7?
    • How important is 2.6?
    • We skipped 2.4 to no ill effects
    • Less maintenance for us
    • 2.6 Checklist: https://github.com/jruby/jruby/issues/5576
    

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12. Getting Started
    

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14. JRuby Install
    • Install a JDK
    • Java 8 recommended, there's many distributions out there
    • Java 9+ work well but may print warnings
    • Install JRuby
    • Recommended: system package, Ruby installer, Docker image
    • Download tarball/zip or Windows installer
    

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15. That's it!
    

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16. Test it out!
    [] ~ $ rvm use jruby
    Using /Users/headius/.rvm/gems/jruby-9.2.6.0
    [] ~ $ irb
    jruby-9.2.6.0 :001 > runtime = java.lang.Runtime.runtime
    => #
    jruby-9.2.6.0 :002 > runtime.available_processors
    => 8
    jruby-9.2.6.0 :003 > runtime.free_memory
    => 91420584
    jruby-9.2.6.0 :004 >
    

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17. Startup Time
    

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18. Why Is This Hard?
    • CRuby: Mostly native code at startup
    • Parser, iseq compiler, iseq interpreter, core classes, extensions
    • JRuby: Mostly interpreted at startup
    • Everything in JRuby starts "cold"
    • JVM eventually optimizes...but it's too late for startup time
    

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19. total execution time (lower is better)
    0s
    1.25s
    2.5s
    3.75s
    5s
    gem --version gem list (~350 gems)
    4.6s
    3.6s
    0.7s
    0.4s
    CRuby JRuby (JDK8)
    

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20. Running in Same JVM
    total execution time (lower is better)
    0s
    1.25s
    2.5s
    3.75s
    5s
    gem list (~350 gems)
    1.3s
    1.6s
    1.6s
    1.6s
    2.2s
    1.7s
    1.7s
    2.0s
    2.2s
    3.5s
    4.6s
    

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21. JRuby Flag: --dev
    • --dev flag
    • export JRUBY_OPTS="--dev"
    • Disables JRuby's JIT
    • Reduces JVM JIT
    • 30-40% reduction
    • Don't forget when benchmarking!
    total execution time (lower is better)
    0s
    1.15s
    2.3s
    3.45s
    4.6s
    gem list (~350 gems)
    3.0s
    4.6s
    JRuby JRuby --dev
    

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22. OpenJDK Class Data Sharing
    • Class Data Sharing
    • Shared JVM class data
    • Reduced memory
    • Improved startup time
    • Install jruby-startup gem
    • Run "generate-appcds"
    • JRuby will use automatically
    total execution time (lower is better)
    0s
    1.75s
    3.5s
    5.25s
    7s
    gem list (~350 gems)
    3.2s
    3.7s
    6.3s
    JRuby --dev --dev + CDS
    

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23. OpenJ9 "quickstart"
    • "quickstart" and "shareclasses"
    • Shares class data across runs
    • Shares JIT results across runs
    • -Xquickstart

    -Xshareclasses:name=whatevs
    • JAVA_OPTS="..."
    total execution time (lower is better)
    0s
    2s
    4s
    6s
    8s
    gem list (~350 gems)
    3.1s
    6.5s
    7.1s
    JRuby --dev --dev + quick
    

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24. Best Times
    total execution time (lower is better)
    0s
    1s
    2s
    3s
    4s
    gem list (~350 gems)
    3.1s
    3.2s
    3.0s
    0.8s
    CRuby JRuby --dev JDK8 JRuby --dev JDK11 CDS JRuby --dev J9 quick
    

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25. Future: Ahead-of-time Compile
    • New JVM tools for precompiling code to native
    • GraalVM's Substrate VM
    • Reduces base VM startup to CRuby speeds
    • Does not help Ruby code loaded at runtime
    • Soon: precompiled JRuby *and* Ruby code
    • App startup as fast as CRuby?
    

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26. total execution time (lower is better)
    0s
    0.45s
    0.9s
    1.35s
    1.8s
    -e 1
    0.5s
    1.7s
    JRuby --dev TruffleRuby native
    total execution time (lower is better)
    0s
    4s
    8s
    12s
    16s
    gem list (~350 gems)
    14.9s
    4.6s
    JRuby --dev TruffleRuby native
    

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27. Gems, Paths, etc
    • Don't share gem path with other Rubies
    • C extension gems have JRuby versions (e.g. Nokogiri)
    • Ruby installers will handle this for you
    • Be mindful if system packages do not
    • Watch out for .ruby-version silently switching
    

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28. Getting Help
    • JRuby on GitHub: https://github.com/jruby/jruby
    • Chat with JRuby devs, users
    • #jruby on Freenode IRC
    • jruby/jruby on Gitter
    • Experimental: jruby on Matrix
    • Mailing list: https://lists.ruby-lang.org
    

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29. JRuby on Rails
    

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30. Why JRuby on Rails?
    • JRuby has run Rails since 2006!
    • "Are there JRuby users running Rails applications?"
    • Oh yes! And at large scale!
    • Benefit from the JVM, libraries, languages
    • The best way to scale large Rails apps today
    

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31. --- testapp_mri_pg/Gemfile
    +++ testapp_jruby_pg/Gemfile
    -# Use postgresql as the database for Active Record
    -gem 'pg', '>= 0.18', '< 2.0'
    +# Use jdbcpostgresql as the database for Active Record
    +gem 'activerecord-jdbcpostgresql-adapter'
    # See https://github.com/rails/execjs#readme for more supported runtimes
    -# gem 'mini_racer', platforms: :ruby
    -
    +gem 'therubyrhino'
    group :development do
    - # Spring speeds up development...
    - gem 'spring'
    - gem 'spring-watcher-listen', '~> 2.0.0'
    end
    Minimal Config Diffs
    --- testapp_mri_pg/config/database.yml
    +++ testapp_jruby_pg/config/database.yml
    @@ -65,5 +81,7 @@
    production:
    <<: *default
    database: rails_prod
    + host: localhost
    + port: 5432
    username: rails_prod
    password: rails_prod
    --- testapp_mri_pg/config/puma.rb 2019-04-19 04:48:51.425474315 +0000
    +++ testapp_jruby_pg/config/puma.rb 2019-04-17 08:56:53.529154189 +0000
    @@ -4,7 +4,7 @@
    # the maximum value specified for Puma. Default is set to 5 threads for minimum
    # and maximum; this matches the default thread size of Active Record.
    #
    -threads_count = ENV.fetch("RAILS_MAX_THREADS") { 2 }
    +threads_count = ENV.fetch("RAILS_MAX_THREADS") { 20 }
    threads threads_count, threads_count
    # Specifies the `port` that Puma will listen on to receive requests; default is 3000.
    @@ -21,7 +21,7 @@
    # Workers do not work on JRuby or Windows (both of which do not support
    # processes).
    #
    -workers ENV.fetch("WEB_CONCURRENCY") { 2 }
    +# workers ENV.fetch("WEB_CONCURRENCY") { 2 }
    # Use the `preload_app!` method when specifying a `workers` number.
    # This directive tells Puma to first boot the application and load code
    

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32. Rails Support Update
    

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33. Rails 5.2.3
    actioncable: some results…hard pg dep for other fails
    actionmailer: 204 runs, 457 assertions, 0 failures, 0 errors
    actionpack: 3174 runs, 15884 assertions, 1 failures, 0 errors
    actionview: 1993 runs, 4398 assertions, 2 failures, 4 errors
    activejob: 180 runs, 415 assertions, 0 failures, 0 errors
    activemodel: 810 runs, 2265 assertions, 0 failures, 0 errors
    activestorage: 144 runs, 372 assertions, 0 failures, 0 errors
    activesupport: 4212 runs, 763229 assertions, 10 failures, 1 errors
    railties: uses fork() [issue #35900]
    99.998% passing!
    

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34. Failure:
    TimeWithZoneTest#test_minus_with_time_precision [activesupport/
    test/core_ext/time_with_zone_test.rb:340]:
    Expected: 86399.999999998
    Actual: 86399.99999999799
    
    

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35. ActiveRecordJDBC 52.2
    • Historic dates
    • PG-specific tests in AR test suite (PRs needed yet)
    • Miscellaneous…
    sqlite3: 19 excludes, 5327 runs, 14961 assertions
    postgresql: 53 excludes, 5915 runs, 16626 assertions
    mysql2: 33 excludes, 5491 runs, 15527 assertions
    

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36. Rails 6.0.0.rc1
    actioncable: 203 runs, 921 assertions, 0 failures, 10 errors
    actionmailbox: 79 runs, 205 assertions, 0 failures, 2 errors
    actionmailer: 220 runs, 509 assertions, 0 failures, 0 errors
    actionpack: 3255 runs, 16027 assertions, 1 failures, 0 errors
    actiontext: 53 runs, 94 assertions, 5 failures, 0 errors
    actionview: 2068 runs, 4667 assertions, 2 failures, 3 errors
    activejob: 301 runs, 659 assertions, 0 failures, 0 errors
    activemodel: 844 runs, 2350 assertions, 0 failures, 0 errors
    activestorage:225 runs, 696 assertions, 0 failures, 0 errors
    activesupport: 4362 runs, 13909 assertions, 15 failures, 1 errors
    99.902% passing!
    

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37. ARJDBC (master - 60.x)
    • 60.0.rc1 is out!
    • Same excludes as 52.x
    • New excludes as we work towards 6.0.0 final
    • Rails 6 apps basically work fine!
    sqlite3: 20 excludes, 6415 runs, 16749 assertions
    postgresql: 89 excludes, 6962 runs, 18289 assertions
    mysql2: 66 excludes, 6535 runs, 17210 assertions
    Daniel Ritz
    

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38. Migrating an App
    

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39. Use-Case: Discourse
    • Big well-known Rails application
    • “A platform for community discussion”
    • >500 gems
    • 250,000 lines of Ruby
    • JRuby is not currently supported
    

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40. JRuby-lint
    See how ready your Ruby code is to run on JRuby
    % gem install jruby-lint
    
    % cd my-app
    
    % jruby-lint
    STEP 1
    

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41. Questionable Gems
    

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42. https://github.com/jruby/jruby/wiki/C-Extension-Alternatives
    

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43. Questionable Assignments?
    

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44. Other Issues…
    

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45. Native C Extensions!
    % bundle install
    STEP 2
    

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46. Strategy: Ignore?
    gem ‘byebug’, platform: :ruby
    

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47. Strategy: Replace with Pure Ruby
    def ruby_xor!(x, y)
    i = 0
    max = (x.length < y.length ? x.length : y.length)
    while i < max
    x.setbyte(i, x.getbyte(i) ^ y.getbyte(i))
    i += 1
    end
    end
    ruby 3.702M (± 5.8%) i/s - 18.431M in 4.995973s
    
    xorcist 11.015M (± 8.1%) i/s - 54.710M in 5.007484s
    Unless the performance matters…
    

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48. Strategy: FFI - Foreign Function Interface
    • Bind to DLL/shared library
    • Call functions & interact with structs/pointers
    • Pure-Ruby syntax!
    • Portable across all Ruby implementations
    

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49. https://github.com/chuckremes/ffi-rzmq-core/blob/master/lib/ffi-rzmq-core/libzmq.rb
    module LibZMQ
    extend FFI::Library
    # ...
    ffi_lib(ZMQ_LIB_PATHS + %w{libzmq})
    attach_function :zmq_strerror, [:int], :pointer, :blocking => true
    # ...
    end
    Load FFI methods
    Load specific DLL
    Attach function
    Nam
    e of function
    Input param
    eters
    Return value
    puts "Error: #{LibZMQ.zmq_strerror(errno)}" Call it just like Ruby!
    

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50. Strategy: Script Java Library
    • JRuby allows call Java classes with Ruby syntax
    • Zillions of existing Java libraries
    • Usually minimal glue code
    

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51. mini_racer port
    • mini_racer is minimal bindings to V8
    • JRuby will script Java library J2V8
    • Native bindings to V8 from Java
    • Someone wrote the C so we don’t have to!
    

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52. mini_racer porting snippets
    require 'mini_racer/jruby/j2v8_linux_x86_64-4.8.0.jar'
    java_import com.eclipsesource.v8.V8
    @v8 ||= V8::createV8Runtime
    JSToRuby(@v8.execute_script(src, file, 0))
    Load Java Library
    Make Java V8 class accessible
    Call method on that class
    Tough to tell we are calling Java here
    

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53. Strategy: Native Java Extension
    • Write the extension in Java
    • Using our extension APIs
    • Generally fastest
    

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54. Porting oj
    • Popular JSON gem
    • 19810 lines of C
    • 7 parsers/dumpers (object, strict, compat, null, custom, rails, wab)
    https://github.com/ohler55/oj
    

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55. JRuby APIs
    @JRubyModule(name = "Oj")
    public class RubyOj extends RubyModule {
    // ...
    @JRubyMethod(module = true, required = 1, rest = true)
    public static IRubyObject strict_load(ThreadContext context,
    IRubyObject self, IRubyObject[] args, Block block) {
    OjLibrary oj = resolveOj(self);
    Options options = oj.default_options.dup(context);
    ParserSource source = processArgs(context, args, options);
    return new StrictParse(source, context, options).parse(oj, true, block);
    }
    }
    Define Oj module
    Define Oj.strict_load
    

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56. Porting Gems Conclusion
    • Pain when replacement does not already exist
    • Many strategies to move past the pain
    • Once someone does it we all get it
    • Yay for Open Source
    

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57. Running JRuby on Rails
    • Puma recommended as server
    • Deployment tools work the same on JRuby
    • Another option: single-file deployment with Warbler
    • JVM will try to use all your memory
    • Tweak JVM heap max with JAVA_OPTS=-Xmx500M
    • JRUBY_OPTS, JAVA_OPTS so child processes pick up flags
    

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

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59. One User's Story
    • Large Rails application using 40 c1.xlarge on EC2
    • 40 Unicorn workers per server
    • 100k-150k requests per minute, 50-75ms response times
    • Migrated app to JRuby, made more use of threading
    • Down to 10 c1.xlarge, 75% cost reduction
    • Consistently over 150k requests per minute, 30ms response times
    

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60. Optimizing for Rails
    • Most important metric for Ruby performance
    • Very difficult framework to optimize
    • See also k0kubun's JIT talk
    • JRuby typically ran a bit slower than CRuby
    • Until recently!
    

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61. Baseline Rails App
    • Simple scaffolded "blog" application
    • EC2 t2.xlarge, Ubuntu 18.04
    • CRuby 2.6.2, JRuby 9.2.7, TruffleRuby RC16
    • what the hell drivers different servers, numbers change
    • for MRI too
    • Workers versus threads briefly
    

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62. requests per second (higher is better)
    0rps
    300rps
    600rps
    900rps
    1200rps
    Scaffolded blog post view
    1,160rps
    1,014rps
    CRuby JRuby
    

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63. Caveats
    • Benchmark driver changes results
    • Keep-alive versus new connections
    • JVM takes time to fully warm up
    • Working on ways to mitigate this
    • Many users drive the system a bit after deploy
    • What about a larger app?
    

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64. rubygems.org performance
    

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65. rubygems.org benchmark
    • Laptop (i7 with 16Gb of memory) (localhost)
    • Production mode force_https = false
    • Puma (JRuby does not support unicorn)
    • All on same machine:
    • rails, postgresql, elasticsearch, toxiproxy, redis, memcached
    • client software: Apache Bench (ab)
    

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66. rubygems.org benchmark
    • http://localhost:9292/profiles/enebo
    • Gem push is not working (toxiproxy?)
    • Benchmark mystery!
    • wrk never would show improvements with multiple threads
    • ab keep alive problems (due to bug #1565 in Puma)
    

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67. Requests/second
    0
    20
    40
    60
    80
    Iteration (30s)
    1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
    JRuby puma single 2.6.2 puma clustered 2.6.2 puma single
    ab -c 1 -t 30s http://localhost:9292/profiles/enebo
    The Warmup Tail
    

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68. Peak Requests/second
    0
    100
    200
    300
    400
    Concurrent threads
    1 2 4 6 8 10 12 14 16 18 20
    JRuby puma single 2.6.2 puma clustered 2.6.2 puma single
    ab -c {n} -t 30 http://localhost:9292/profiles/enebo
    3 16
    

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69. Memory Usage
    Memory (RES)
    0
    1000
    2000
    3000
    4000
    # of test runs
    1 Run (35 mins) 6 Runs 11 Runs 16 Runs 21 Runs
    1,536
    1,536
    1,536
    1,434
    1,228
    3,620
    3,540
    3,460
    3,340
    3,060
    CRuby (20 workers) JRuby (20 threads, 384m heap)
    +8.4%
    +14.4%
    +4.5%
    +6.7% +0%
    2.5x smaller
    +0%
    +3.3% +3.2%
    

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70. Scaling Takeaways
    + Uses less memory (threads vs processes)
    • Whole duplicated stack + app uses more memory
    + More memory stable over time
    • CoW? Fragmenting in GC? Memory leak?
    + More CPU efficient
    • More error tolerant on same hardware
    – More warmup time
    

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71. Wrapping Up
    

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72. JRuby Futures
    • Ruby 2.6 or 2.7?
    • Stop by chats and let us know
    • Native-compiling JRuby for startup time
    • Upcoming JVM features: true fibers, built-in FFI, new JITs and GCs
    

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73. JRuby on Rails Futures
    • Rails 6 is working today
    • Continue getting more tests green, JRuby in CI
    • We're here when you need us
    • As your app grows, JRuby can help you scale
    • Reduce resources, save money
    • Start with JRuby or keep it in mind as you go
    

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75. Help Wanted!
    • New features, Rails tests are great opportunities!
    • Learn more about how Ruby and JRuby work
    • Help us keep up with Ruby development
    • We are always standing by to help you!
    

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76. Try JRuby!
    Let us know how it goes!
    

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77. Thank You!
    • Charles Oliver Nutter
    • headius@headius.com
    • @headius
    • Tom Enebo
    • tom.enebo@gmail.com
    • @tom_enebo
    • http://jruby.org
    • Ruby 2.6 checklist:

    https://github.com/jruby/jruby/issues/5576
    

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