Introduction to Ruby from my Ruby on Rails and PostgreSQL - Intro to Advanced class in August 2014.

1. jRuby

2. jRuby: Why?
Ruby isn’t perfect
• Some gems can create memory leaks
– esp. if they were written with native C
• Does not have kernel level threading
– Global Interpreter Lock
• Everything is an object means unnecessary
processing happens when doing things like
adding numbers leading to a performance hit

3. jRuby: So how does it fix things?
I hate writing Java…but the JVM is a work of art
• Java infrastructure is virtually bulletproof
– Most mature way to deploy a web application
– Enterprisey 
• JVM’s garbage collector is best of breed and eliminates the potential
memory leak issues
• JVM’s Just-In-Time compiler continually optimizes code the longer it runs
making it faster
• JVM gives Ruby kernel level threading
• jRuby inspects your Ruby code to see if you’re doing anything it would
prefer you didn’t…and turns it off if you’re not
– Eg. If you aren’t overloading the + operator on int’s, it will convert them to
basic types instead of running as objects
• Include and use very mature Java libraries directly in your Ruby code
– Significantly expands your toolbelt
– Allows easy integration into existing Java environments

4. The Sidekiq Test
Sidekiq is a multithreaded background
worker that provides tremendous
concurrency benefits
Creating 1,000,000 objects in 50
concurrent threads
Ruby
jRuby

5. The App Server Test
CPU Usage

6. The App Server Test
Free Memory

7. The App Server Test
Latency

8. The App Server Test
Throughput

9. “Warming up the JVM”
• Important term for benchmarking
• Translation
– Run enough requests through the system for the
JIT compiler to optimize the code. Code will get
faster and more RAM efficient the longer it runs.

10. Update and Clarification
• As of this posting to Slideshare, Torquebox has a mature version 3
and a prototype version 4 that operates in a “web server only”
mode. Ruby is at version 2.1.0 with dramatic improvements to
memory performance with forking which allows higher
concurrency.
• At this time, jruby it’s much closer. Based on chatter from the
#jruby IRC channels, a major new release of both jRuby and
Torquebox are expected to dramatically improve their performance
thanks to recent Java updates. The expected timeline was late 2014
last I heard.
• Independent benchmarks can be found here:
http://www.techempower.com/benchmarks/#section=data-
r9&hw=peak&test=json

11. As for those benchmarks

12. Use Java libraries IN Ruby
require ‘java’
java_import ‘java.lang.System’
System.gc()
# Call the Java Garbage Collector
# You don’t need to do this, just an example
# More http://bbll.us/WcJZbM

13. JARs!
require 'path/to/mycode.jar’
# Reference as full package
Java: org.foo.department.Widget
Ruby: Java::OrgFooDepartment::Widget
# Without full package
java_import java.lang.System
version = System.getProperties["java.runtime.version"]

14. So, how do you use it?
Convert your application
• Switch to jRuby with RVM
• Define jRuby as your engine
• gem install jruby-lint
• Run jrlint to check Gems
– Replace where needed
• Switch your database
connection adapter
Then DEPLOY
• Use a Java server just like
you currently use Ruby
servers
– Puma
– Torqbox
• OR create a .war file
– Deploy anywhere Java can
• OR use a Ruby-ized Java
Application Server
– Trinidad (aka – Tomcat)
– Torquebox (aka – Jboss)

15. WHAT’S AN APPLICATION SERVER?
It’s my stack in a box 

16. Torquebox / JBoss
• Web Server
• Background Jobs
• Queuing
• Job Scheduling
• Daemon Processes
• Infinispan
– faster memcached
• Pub/Sub
• Clustering
– of everything
• Rolling Deployments
– Across the cluster
• Load balancing
– of everything
• Unique execution
– Across the cluster
• Deploy multiple apps
– In one cluster
– Share/Separate resources
– Console equivalent

17. Any important relationships?
• jRuby core developers
• Torquebox core developers
• Same people.
• jRuby advancements are leveraged by
Torquebox first
• Torquebox is the fastest server for a reason

18. LET’S CONVERT YOUR APP