JRuby: Zero to Scale Thomas E. Enebo (@tom_enebo) Charles O. Nutter (@headius)

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

What is JRuby? Ruby Implementation (2.5.7 compatible) …which happens to run on the Java Virtual Machine (JVM)

JRuby 9.2.9.0 • Lots of memory and startup time improvements • Better support for Java module system • .jruby.java_opts file to manage JVM options • Improved startup time for most commands • Dozens of issues fixed

Getting JRuby in 3 Steps

Step 1: You Need a JVM • Java (version 8 or 11 recommended) • Is it installed? java -version • If !installed • package install: dnf/apt install java • explicit install: http://adoptopenjdk.net

Step 2: Install JRuby

Step 2: Install JRuby on Windows www.jruby.org

Step 3: Profit!

Why JRuby? What are the differences? - JRuby - C Ruby

Native Threads vs Global Interpreter Lock

require 'benchmark' ary = (1..1000000).to_a loop { puts Benchmark.measure { 10.times { ary.each {|i|} } } } Unthreaded require 'benchmark' ary = (1..1000000).to_a loop { puts Benchmark.measure { (1..10).map { Thread.new { ary.each {|i|} } }.map(&:join) } } Multi-threaded

Ruby 2.5.7 unthreaded JRuby unthreaded Ruby 2.5.7 threaded JRuby threaded

Time (in seconds) 0 0.09 0.18 0.27 0.36 Unthreaded Threaded 0.15 0.23 0.35 0.34 CRuby JRuby (lower is better)

Virtual Machine vs Going It Alone

Ruby Teams Hiro Marcin Nahi Subbu Douglas Christian Karol Tom Charlie Hiro charli Nahi zzak nurse hsbt matz ko1 nobu OS (libc, ...) JRuby MRI

Ruby Teams Hiro Marcin Nahi Subbu Douglas Christian Karol Tom Charlie Hiro charli Nahi zzak nurse hsbt matz ko1 nobu OS (libc, ...) JRuby MRI JVM POSIX

JVM Ruby Teams Hiro Marcin Nahi Subbu Douglas Christian Karol Tom Charlie Hiro charli Nahi zzak nurse hsbt matz ko1 nobu OS (libc, ...) JRuby MRI Better ??? POSIX

!Perspective! ??? Total control can be great!

Shoulders of Giants JVM J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose Hiro Marcin Nahi Subbu Douglas Christian Dmitry Tom Charlie JRuby

All the stuff! JVM J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose J. Rose Garbage Collection Native JIT Profiled Optimizations Native Threading Tooling Cross Platform

Alternate JVMs • Hotspot: standard OpenJDK Java VM • OpenJ9: open source version of IBM's J9 JVM • New GC and JIT tuning options • Startup time and JIT code-caching features • GraalVM: replaces Hotspot JIT with Graal JIT • New JIT optimizations, ahead-of-time native compilation

JVM is everywhere++! • Unix++, Windows • Exotic platforms: zLinux, OpenVMS, AS/400 • Mobile: Android’s Dalvik, Embedded JVMs

Java bytecode == portability

actionmailer-javamail, active_documentum, activerecord-jdbc-adapter, activerecord-jdbcdbf-adapter, activerecord-jdbcderby-adapter, activerecord-jdbch2-adapter, activerecord-jdbchsqldb-adapter, activerecord-jdbcmssql-adapter, activerecord-jdbcmysql-adapter, activerecord-jdbcpostgresql-adapter, activerecord-jdbcsqlite3- adapter, activerecord-netezza-adapter, activerecord-vertica-adapter, akephalos, akephalos-nerian, akephalos2, akka-actor-jars, akka-remote-jars, akubra_llstore_migrate, Antwrap, async-http-client-jars, atomic, atoulme-Antwrap, autotest-java, bbrowning-deltacloud-client, bbrowning-deltacloud-core, bcrypt- ruby, bee_java, berkeley-db-java-jars, bert, bio-maf, blockenspiel, boc, bond, bosdk, bouncy-castle-java, boxed-geminabox, brute-fuzzy, bryanl-gherkin, bson, buby, buildr, buildr-resolver, buildrizpack, butternut, capistrano-java, capybara-java_script_lint, carrierwave-neo4j, carrierwave_imagevoodoo, cassandra-jars, chrest, cloby, commons-io-jars, concurrently, contextual, coupler, cucumber-java, cucumber-jvm, cuke4duke, cuuid, dm-ldap-adapter, dm-lucene-adapter, do-jdbc_sqlserver, do_derby, do_h2, do_hsqldb, do_jdbc, do_mysql, do_openedge, do_oracle, do_postgres, do_sqlite3, do_sqlserver, doubleshot, dripdrop, dubious, duby, engineyard-visualvm, epall-limelight, errbit_zmq_handler, eurydice, euston, euston-daemons, euston-eventstore, euston-projections, euston-rabbitmq, euston- websites, eventmachine, excemel, faye-websocket, ffi, fig, file-find, fishwife, foreman, forkit, forkjoin, gamelan, gemshit, geoip-jars, get_back, gherkin, glassfish, gravitext-util, gravitext-xmlprod, grizzly, guava-jars, hadoop-find, hashdot-test-daemon, hiredis, hitimes, hope, hostor, hot_bunnies, hourglass, hpricot, http_parser.rb, inline_javascript, iudex, iudex-async-httpclient, iudex-barc, iudex-brutefuzzy-protobuf, iudex-brutefuzzy-service, iudex-char-detector, iudex-core, iudex-da, iudex-filter, iudex-html, iudex-http, iudex-http-test, iudex-httpclient-3, iudex-jetty-httpclient, iudex-rome, iudex-simhash, iudex-worker, ivy-jars, iyyov, jactive_support, java-autotest, java-inline, java2ruby-xmldsig, java_bin, java_inline, java_override, java_properties, java_streamify, java_testing_guff, javabean_xml, javaclass, javaeye4r, javagems, javajake, javaobj, javaobjs, javaobs, javaparse, javasand, javascript-securehash-rails, javascript-state-machine-rails, javascript_auto_include, javascript_eraser, javascript_features, javascript_i18n, javascript_localize, javascript_safe_logger, javascript_util_asset_pack, javascripto, javascripto-rails, jdbc-derby, jdbc-hsqldb, jdbc-jtds, jdbc-openedge, jdbc-openedge-internal, jdbc-postgres, jdbc-sqlite3, jedis-jars, jena-jruby, jessica, jettr, jetty, jetty- jsp, jgeoip, jms4r, jpdfer, jrack_handlers, jrtm, jruby-activemq, jruby-akka_jars, jruby-elasticsearch_jars, jruby-httpclient, jruby-launcher, jruby-management, jruby- metrics, jruby-pageant, jruby-vijava, jruby_gc_stats, jruby_sandbox, jruby_threach, jrubyconf-button, jsmetric4java, json, json-jruby, jsound, kb-activerecord-jdbc- adapter, kirk, kyotocabinet-java, ladle, latex-decode, launchy, libnotify, limelight, linecache, logback, logback-jars, looksee, lumix, mack-javascript, markdownj, maven_irb_plugin, metrics-core-jars, metrics-java, mguymon-buildr, mikka, mini_aether, mirah, mirah_model, miso-java, mixology, mm_mq, mongrel, msgpack-idl- java, msgpack-jruby, multimeter, naether, nanoc-javascript-concatenator, neo4j, neo4j-admin, neo4j-advanced, neo4j-community, neo4j-core, neo4j-enterprise, neo4j-spatial, neo4j-will_paginate, neo4j-wrapper, netty-jars, ning-compress-jars, nio4r, nokogiri, nokogiri-fitzsimmons, nokogiri-maven, nosqoop4u, ontomde- demo-java5, ontomde-java, ontomde-java-frontend, ontomde-uml2-java, ontomde-uml2-kbjava, open_nlp, pacer, pacer-dex, pacer-neo4j, pacer-orient, pelops-jars, persvr, pg_array_parser, protobuf-jars, pry, puma, qtjruby-core, qwirk_active_mq_adapter, qwirk_jms_adapter, rabbitmqadmin-cli, ragweed, rails_javascript_helpers, rakejava, rave, rcov, realityforge-jekyll, realityforge-jekylltask, redcar-bundles, redcar-clojure, redcar-filter-through-command, redcar- groovy, redcar-icons, redcar-javamateview, redcar-javascript, redcar-mirah, redcar-svnkit, redcar-xulrunner-win, RedCloth, refinerycms-javascripts, reigns, revo- nokogiri, rika, rjack-async-httpclient, rjack-commons-codec, rjack-commons-dbcp, rjack-commons-dbutils, rjack-commons-pool, rjack-httpclient-3, rjack- httpclient-4, rjack-icu, rjack-jackson, rjack-jdom, rjack-jets3t, rjack-jetty, rjack-jetty-jsp, rjack-jms, rjack-jms-spec, rjack-logback, rjack-lucene, rjack-maven, rjack- mina, rjack-nekohtml, rjack-protobuf, rjack-qpid-client, rjack-rome, rjack-slf4j, rjack-solr, rjack-tarpit, rjack-xerces, rmagick4j, rmodbus, rtm-javatmapi, rtm- majortom, rtm-ontopia, rtm-tinytim, rtm-tmql, rubeus, rubinius-core-api, ruby-blockcache, ruby-debug-base, ruby-maven, ruby2java, rubydoop, rubyjedi- nokogiri_java, scala-inline, scala-library-jars, scriptty, slf4j, slf4j-jars, slyphon-zookeeper, slyphon-zookeeper_jar, smackr, smartimage, SNMP4JR, solr_sail, spiegela- jruby-httpclient, sproutcore, spymemcached, sqldroid, steamcannon-deltacloud-client, steamcannon-deltacloud-core, stilts-stomp-client, supermarket, svm_toolkit, swt, theduke, thick, to-javascript, torquebox-base, torquebox-cache, torquebox-configure, torquebox-container-foundation, torquebox-core, torquebox- messaging, torquebox-messaging-container, torquebox-naming, torquebox-naming-container, torquebox-security, torquebox-server, torquebox-vfs, torquebox- web, twitter4j4r, UDJrb, unageanu-javaclass, unimidi, universe-javascript, url_escape, weakling, webbit-jars, wildnet-jackson, wildnet-netty, wildnet-server, wildsonet-hazelcast, wildsonet-netty, wildsonet-server, wildsonet-streamer, wrest, wrong, xdojava, xqruby, zookeeper No build tools!

Ruby C Extensions vs Java Native Extensions

Why Extensions? • Performance • Access Existing Library (e.g. openssl)

C Extensions • API is massive • API is specific to C Ruby’s implementation • It is the implementation • At odds with concurrent Ruby execution • Huge support cost

Java Native Extensions • API is massive • API is specific to JRuby’s implementation • It is the implementation* • Allows Concurrent Ruby Execution • Support cost minimal • Common Gems Supported * We have plans for a formal API

oj: Optimized json • Fast json parsing and dumping with many options • Common transitive dependency with its own API • Needed for many popular apps/libraries https://github.com/ohler55/oj

oj for JRuby! • 9200 lines of Java (vs 20k lines of C) • Almost ready: 448 runs, 765 assertions, 43 failures, 12 errors • 35 F/E from minor features, date/time diffs

Load Performance 0M 0.3M 0.6M 0.9M 1.2M small medium large 0.13 0.29 1.1 0.05 0.11 0.36 0.06 0.11 0.72 MRI (oj) JRuby (json) JRuby (oj) Millions of loads per second (higher is better) https://techblog.thescore.com/2014/05/23/benchmarking-json-generation-in-ruby/

Dump Performance 0 0.75 1.5 2.25 3 small medium large 0.44 0.86 2.3 0.22 0.44 1.1 0.33 0.73 2.1 MRI (oj) JRuby (json) JRuby (oj) Million of dumps per second (higher is better) https://techblog.thescore.com/2014/05/23/benchmarking-json-generation-in-ruby/

Scripting Java

Scripting Java • Access Java Classes using a Ruby Syntax • Java Libraries • Give alternatives to existing Ruby Libraries • Give access to APIs which do not exist in Ruby

JRuby IRB

Fun Stuff event(:player_egg_throw) do |e| e.hatching = true e.num_hatches = 120 e.player.mesg "hatched" end Purugin https://github.com/enebo/Purugin

JRuby Performance

Startup Time • Runtime optimizations give us excellent performance • ...eventually! • Startup time, warmup time are impacted • We continue working to reduce this impact • We compare some common commands

JRuby Architecture Ruby (.rb) JIT Java Instructions (java bytecode) Ruby Instructions (IR) parse interpret interpreter interpret C1 compile native code better native code java bytecode interpreter execute C2 compile Java Virtual Machine JRuby Internals deoptimize Performance improves the longer your app runs

JRuby Flag: --dev • export JRUBY_OPTS="--dev" • Disables JRuby's JIT • Reduces JVM JIT • Don't use when benchmarking! • 30-40% reduction • More improvements coming 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

0 1 2 3 4 gem list 3.05 0.939 CRuby JRuby --dev

0 1.75 3.5 5.25 7 rails console 6.7 4.96 CRuby JRuby --dev

OpenJDK Class Data Sharing • Pre-validate and cache class data • Save frequently-accessed data over time • Combined with --dev gives best current JRuby startup

Java 11 total execution time (lower is better) 0 1.75 3.5 5.25 7 gem list (~350 gems) JRuby --dev --dev + CDS

App Performance • Sinatra and Roda • https://github.com/CaDs/ruby_benchmarks • Comparing JRuby, CRuby, and TruffleRuby • RedMine bug tracker and wiki • https://www.redmine.org/ • Real-world Rails application on JRuby, CRuby

Peak Performance • After initial startup, warmup, data caching • JRuby generally gives better peak performance • Be aware of warmup time

Sinatra and Roda requests/second (higher is better) 0 12500 25000 37500 50000 Sinatra Roda 5,214 4,257 44,703 42,468 14,489 12,284 CRuby JRuby TruffleRuby

Redmine Issue View, rendered and json (higher is better) 0 req/s 35 req/s 70 req/s 105 req/s 140 req/s issues/13 issues/13.json 137 req/s 50 req/s 91 req/s 41 req/s CRuby 2.6.2 JRuby 9.2.9

Warmup Time • Large applications take longer to warm up • Working on new JIT metrics, profiling to reduce this curve

Sinatra performance over time, requests/second 0rps 12500rps 25000rps 37500rps 50000rps 5s 10s 15s 20s 25s CRuby JRuby

Roda performance over time, requests/second 0rps 12500rps 25000rps 37500rps 50000rps 5s 10s 15s 20s 25s CRuby JRuby

Redmine issues/13.json warmup, one-minute cycles 0 35 70 105 140 1st 2nd 3rd 4th 5th 6th CRuby 2.6.2 JRuby 9.2.9

Redmine memory usage (lower is better) 0MB 375MB 750MB 1125MB 1500MB Memory usage for 8 workers vs 8 threads 800MB 1,430MB 1,100MB CRuby JRuby (default) JRuby (300MB heap)

Migrating An App

Migration Process • Existing application Activities: • Configuration Changes (e.g. config/database.yml) • C extensions replacement • Thread-safety audit

Use-Case: Discourse • “A platform for community discussion” • Very large, well-known Rails application • >500 gems • 250,000 lines of Ruby • JRuby is not currently supported • But it is almost working!

Step 1: jruby-lint

jruby-lint gem See how ready your Ruby code is to run on JRuby $ gem install jruby-lint $ cd my-app $ jrlint

[] ~/projects/discourse $ jrlint JRuby-Lint version 0.9.0 ./Gemfile:: [gems, info] For more on gem compatibility see http://wiki.jruby.org/C-Extension-Alternatives ./Gemfile:80: [gems, warning] Found gem 'oj' which is reported to have some issues: Try `gson`, `json` or `json_pure` instead.| gem 'oj' ./Gemfile:81: [gems, warning] Found gem 'pg' which is reported to have some issues: Use activerecord-jdbcpostgresql-adapter instead or pg_jruby (drop-in replacement).| gem 'pg' ./Gemfile:187: [gems, warning] Found gem 'mysql2' which is reported to have some issues: Use activerecord-jdbcmysql-adapter.| gem 'mysql2' ./Gemfile:188: [gems, warning] Found gem 'redcarpet' which is reported to have some issues: Same as with **RDiscount** use alternatives such as kramdown, Maruku or markdown_j| gem 'redcarpet' ./Gemfile:189: [gems, warning] Found gem 'sqlite3' which is reported to have some issues: Use activerecord-jdbcsqlite3-adapter.| gem 'sqlite3', '~> 1.3.13' ./app/mailers/user_notifications.rb:152: [nonatomic, warning] Non-local operator assignment (@popular_topics) is not guaranteed to be atomic. @popular_topics = topics_for_digest[0, SiteSetting.digest_topics] ./app/mailers/user_notifications.rb:630: [nonatomic, warning] Non-local operator assignment (@site_name) is not guaranteed to be atomic. @site_name = SiteSetting.email_prefix.presence || SiteSetting.title # used by I18n ./app/models/report.rb:21: [nonatomic, warning] Non-local operator assignment (@start_date) is not guaranteed to be atomic. @start_date ||= Report.default_days.days.ago.utc.beginning_of_day ./app/models/report.rb:22: [nonatomic, warning] Non-local operator assignment (@end_date) is not guaranteed to be atomic. @end_date ||= Time.now.utc.end_of_day ./app/models/admin_dashboard_next_data.rb:17: [nonatomic, warning] Non-local operator assignment (@json) is not guaranteed to be atomic. @json ||= get_json ./app/models/topic_posters_summary.rb:31: [nonatomic, warning] Non-local operator assignment (@descriptions_by_id) is not guaranteed to be atomic. @descriptions_by_id ||= begin ./app/models/topic_posters_summary.rb:33: [nonatomic, warning] Non-local operator assignment (descriptions[id]) is not guaranteed to be atomic. descriptions[id] ||= [] ./app/models/topic_posters_summary.rb:79: [nonatomic, warning] Non-local operator assignment (@avatar_lookup) is not guaranteed to be atomic. @avatar_lookup ||= options[:avatar_lookup] || AvatarLookup.new(user_ids) ./app/models/topic_posters_summary.rb:83: [nonatomic, warning] Non-local operator assignment (@primary_group_lookup) is not guaranteed to be atomic. @primary_group_lookup ||= options[:primary_group_lookup] || PrimaryGroupLookup.new(user_ids) ./app/models/directory_item.rb:8: [nonatomic, warning] Non-local operator assignment (@headings) is not guaranteed to be atomic. @headings ||= [:likes_received, ./app/models/directory_item.rb:18: [nonatomic, warning] Non-local operator assignment (@types) is not guaranteed to be atomic. @types ||= Enum.new(all: 1, ./app/models/group_history.rb:11: [nonatomic, warning] Non-local operator assignment (@actions) is not guaranteed to be atomic. @actions ||= Enum.new( ./app/models/locale_site_setting.rb:10: [nonatomic, warning] Non-local operator assignment (@values) is not guaranteed to be atomic. @values ||= supported_locales.map do |locale| ./app/models/locale_site_setting.rb:25: [nonatomic, warning] Non-local operator assignment (@language_names) is not guaranteed to be atomic. @language_names ||= begin ./app/models/locale_site_setting.rb:41: [nonatomic, warning] Non-local operator assignment (@supported_locales) is not guaranteed to be atomic. @supported_locales ||= begin ./app/models/category.rb:98: [nonatomic, warning] Non-local operator assignment (TOPIC_CREATION_PERMISSIONS) is not guaranteed to be atomic. TOPIC_CREATION_PERMISSIONS ||= [:full] ./app/models/category.rb:99: [nonatomic, warning] Non-local operator assignment (POST_CREATION_PERMISSIONS) is not guaranteed to be atomic. POST_CREATION_PERMISSIONS ||= [:create_post, :full] ./app/models/category.rb:109: [nonatomic, warning] Non-local operator assignment (@topic_id_cache) is not guaranteed to be atomic. @topic_id_cache = DistributedCache.new('category_topic_ids') ./app/models/category.rb:228: [nonatomic, warning] Non-local operator assignment (@@cache) is not guaranteed to be atomic. @@cache ||= LruRedux::ThreadSafeCache.new(1000) ./app/models/category.rb:520: [nonatomic, warning] Non-local operator assignment (@has_children) is not guaranteed to be atomic. @has_children ||= (id && Category.where(parent_category_id: id).exists?) ? :true : :false

Unsupported Extensions ./Gemfile:: [gems, info] For more on gem compatibility see http://wiki.jruby.org/C-Extension-Alternatives ./Gemfile:80: [gems, warning] Found gem 'oj' which is reported to have some issues: Try `gson`, `json` or `json_pure` instead.| gem 'oj' ./Gemfile:81: [gems, warning] Found gem 'pg' which is reported to have some issues: Use activerecord-jdbcpostgresql-adapter instead or pg_jruby (drop-in replacement).| gem 'pg' ./Gemfile:187: [gems, warning] Found gem 'mysql2' which is reported to have some issues: Use activerecord-jdbcmysql-adapter.| gem 'mysql2' ./Gemfile:188: [gems, warning] Found gem 'redcarpet' which is reported to have some issues: Same as with **RDiscount** use alternatives such as kramdown, Maruku or markdown_j| gem 'redcarpet' ./Gemfile:189: [gems, warning] Found gem 'sqlite3' which is reported to have some issues: Use activerecord-jdbcsqlite3-adapter.| gem 'sqlite3', '~> 1.3.13'

No content

Threading Concerns ./app/models/report.rb:21: [nonatomic, warning] Non-local operator assignment (@start_date) is not guaranteed to be atomic. @start_date ||= Report.default_days.days.ago.utc.beginning_of_day ./app/models/report.rb:22: [nonatomic, warning] Non-local operator assignment (@end_date) is not guaranteed to be atomic. @end_date ||= Time.now.utc.end_of_day ./app/models/admin_dashboard_next_data.rb:17: [nonatomic, warning] Non-local operator assignment (@json) is not guaranteed to be atomic. @json ||= get_json ./app/models/topic_posters_summary.rb:31: [nonatomic, warning] Non-local operator assignment (@descriptions_by_id) is not guaranteed to be atomic. @descriptions_by_id ||= begin ./app/models/topic_posters_summary.rb:33: [nonatomic, warning] Non-local operator assignment (descriptions[id]) is not guaranteed to be atomic. descriptions[id] ||= [] ./app/models/topic_posters_summary.rb:79: [nonatomic, warning] Non-local operator assignment (@avatar_lookup) is not guaranteed to be atomic. @avatar_lookup ||= options[:avatar_lookup] || AvatarLookup.new(user_ids) ./app/models/topic_posters_summary.rb:83: [nonatomic, warning] Non-local operator assignment (@primary_group_lookup) is not guaranteed to be atomic. @primary_group_lookup ||= options[:primary_group_lookup] || PrimaryGroupLookup.new(user_ids) @language_names) is not guaranteed to be atomic. @language_names ||= begin

Unsupported Features ./script/measure.rb:48: [objectspace, warning] Use of ObjectSpace is expensive and disabled by default. Use -X+O to enable. ObjectSpace.each_object do |o| ./script/check_forking.rb:14: [fork, error] Kernel#fork is not implemented on JRuby. child = fork do ./script/check_forking.rb:17: [fork, error] Kernel#fork is not implemented on JRuby. grand_child = fork do

Step 2: Replace C Extensions

% bundle install Fetching pg 1.1.4 Installing pg 1.1.4 with native extensions Gem::Ext::BuildError: ERROR: Failed to build gem native extension gem 'pg' Gemfile Gemfile gem 'pg', platform: :mri gem 'activerecord-jdbcpostgresql-adapter', platform: :jruby

Missing C Extension 1.Remove it if not needed (development dep like byebug) 2.Use a pure-Ruby version if performance is good enough 3.Call into a native library using FFI (Foreign Function Interface) 4.“Script” a Java library 5.Write a JRuby extension

Step 3: Run It • Once your application bundles, it should run! • If not talk to us or file an issue puma -t 20:20 -e production

Monitoring and Profiling

JVM Tooling • Visual VM: monitor and profile threads, GC, managed heap • Mission Control: visualize Flight Recorder output • Flight Recorder: low-overhead system profiling in OpenJDK • async-profiler: command line profiles, flame graphs of CPU, alloc • All JVM tools work to monitor and profile JRuby apps

VisualVM • Standalone graphical console for monitoring, profiling • Open sourced as part of OpenJDK project • https://visualvm.github.io/

No content

Visual VM and Visual GC

JDK Flight Recorder • JVM flag: -XX:+FlightRecorder • JRuby flag: -J-XX:+FlightRecorder or put in JAVA_OPTS • Add --flight-recorder to JRuby launcher? • No overhead or profiling until you start recording • And usually less than 1% overhead for that

JDK Mission Control • Control center and visualizer for Flight Recorder data • Start and manage recordings • Browse recorded data • https://adoptopenjdk.net/jmc.html

No content

No content

No content

No content

No content

No content

async-profiler • JVM extension for lightweight sampled profiles • Install jruby-async-profiler gem • jruby -J-agentpath:/lib/libasyncProfiler.so • Simplified command lines coming soon • See https://github.com/jvm-profiling-tools/async-profiler

No content

Final Words

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

During Development • JRUBY_OPTS=--dev • BE WARY of .ruby-version • Don’t share gem paths between Ruby implementations • Java and C extensions clobber each other

Java Modules • Java 9+ introduced Java Modules • You'll see warnings about JRuby or Ruby accesses • New config file for JVM flags: .jruby.java_opts • Gather JVM options into a single file • Current dir, home dir, JRuby bin/ dir

Java Modules and .jruby.java_opts WARNING: An illegal reflective access operation has occurred WARNING: Illegal reflective access by org.bouncycastle.jcajce.provider.drbg.DRBG (file:/Users/headius/.m2/repository/org/ bouncycastle/bcprov-jdk15on/1.61/bcprov-jdk15on-1.61.jar) to constructor sun.security.provider.Sun() WARNING: Please consider reporting this to the maintainers of org.bouncycastle.jcajce.provider.drbg.DRBG WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations WARNING: All illegal access operations will be denied in a future release --add-opens java.base/java.io=org.jruby.dist --add-opens java.base/java.nio.channels=org.jruby.dist --add-opens java.base/sun.nio.ch=org.jruby.dist --add-opens java.management/sun.management=org.jruby.dist

Try JRuby!

Let us know if you have any questions!

Thank You! • @headius, @tom_enebo • https://www.jruby.org • https://github.com/jruby/jruby • Chat with JRuby devs, users • #jruby on Freenode IRC • jruby on Matrix • Mailing list: https://lists.ruby-lang.org