The Good, The Bad & The Ugly (Clojure & JRuby) Allen - - PowerPoint PPT Presentation

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The Good, The Bad & The Ugly (Clojure & JRuby) Allen - - PowerPoint PPT Presentation

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The Good, The Bad & The Ugly (Clojure & JRuby) Allen Rohner @arohner @circleci Clojure/West 2012 Monday, March 19, 12 Who Am I Using Clojure in production since 2008 Author of Scriptjure, a DSL for writing javascript, two

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The Good, The Bad & The Ugly

(Clojure & JRuby)

Allen Rohner @arohner @circleci Clojure/West 2012

Monday, March 19, 12

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Who Am I

  • Using Clojure in production since 2008
  • Author of Scriptjure, a DSL for writing

javascript, two years before ClojureScript

  • Commits in Clojure core, contrib, ring,

compojure, noir, lein, swank-clojure, pallet...

Monday, March 19, 12

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Circle

  • Founder
  • CircleCI.com
  • Easy Continuous Integration for web apps

Monday, March 19, 12

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When this talk was accepted....

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TL;DR

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It Is NOT about:

  • “Ruby sucks”
  • “JRuby sucks”

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It Is NOT about:

  • “Ruby sucks”
  • “JRuby sucks”

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It IS about

Ruby != Clojure

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My Biases

  • 2006-2009: Rails 1.x
  • 2008-2012: Clojure
  • Expert in Clojure, Intermediate in Ruby

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My History

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How did we get into this mess?

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Mongo Clojure JRuby Trinidad

Architecture

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The Good

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Calling just works

(require ‘foo.bar) (foo.bar/baz 3) foo = JRClj.new(“foo.bar”) foo.baz(3) (-> (r/module “Foo”) (r/class “Bar”) (r/send :baz 3)) Foo::Bar.baz(3)

Monday, March 19, 12

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Fork Me

  • https://github.com/kyleburton/jrclj
  • https://github.com/circleci/cljr

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The Clojure REPL makes Ruby better

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Individual tests

  • (r/rspec “specs/controllers/foo.rb”)
  • (r/rspec “-e” “that one test”)*

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Fine-grained reloading

  • (r/eval “load ./foo.rb”)

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Clojure Concurrency from JRuby

  • Worker.send_email()
  • concurrency with no queues

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Runtimes!

  • (r/new-runtime)
  • (def server (r/rails-server))

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JRuby Runtimes

The JVM Ruby 1 Ruby 2 Ruby 3

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Combining WARs

  • Warbler
  • lein war
  • Deploy both on tomcat/jetty
  • (Not tested)

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JRuby

  • Impressive technology
  • awesome maintainers

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The Bad

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But...

  • Stuck on 1.6.5, couldn’t upgrade or

downgrade due to different bugs

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1.9

  • 1.9 support not finished
  • Encoding
  • SSL

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Complexity

kLOC Java Self- hosted Clojure (1.3.0) JRuby (1.6.5)

51 28 291 600

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Gems

  • Often not tested against JRuby
  • ExecJS
  • Some just can’t work in JRuby
  • FFI

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Slow Startup

  • Ruby likes to restart, early & often
  • helpers, rack middleware

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Slow Startup

  • 1:03 macbook pro
  • 1:45 macbook air
  • 3:00 ec2 m1.small

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Slow Startup Matters

  • need to RSpec all the time
  • Spork & Guard didn’t work
  • rake tasks (generate, etc)
  • rake assets:precompile (8m)

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Dilemma:

  • slow restart
  • strangeness caused by Ruby code not

expecting to reload

  • Restart often, just in case

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Setup

  • Paul lost 2 days

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CRuby in Dev, JRuby in production

Doesn’t work!

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Different Views

  • Clojure likes one big process, lots of

threads

  • Ruby prefers lots of small processes
  • Multithreaded JRubyOnRails: works in

theory, not in practice. Weird classloading bugs, unsupported gems.

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Duplication

  • DB connections
  • DB models
  • Test data

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Classpath

  • Different depending on whether you ran

‘rails console’ or ‘lein repl’

  • => different behavior
  • Can be fixed, but it’s one more headache
  • If you didn’t understand that, yes

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Rails Env

  • DB connection
  • Email policy
  • Class reloading
  • error reporting
  • Airbrake

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Clojure Environment

  • Clojure leaves that to you
  • * (yes there’s Noir’s env, but it’s minor

compared to what Rails does)

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Testing

  • Rails loves to mock
  • Clojure prefers pure fns

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Rails Testing Env

  • FactoryGirl returning fake objects
  • DB Cleared between tests
  • But who told Clojure?
  • Are you both talking to the same DB?

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The Ugly

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Naming

  • project.git-url =>

project[“git-url”]

  • (mongo/update! :project

{:git_url git-url}))

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Symbols vs. Keywords

  • Wrappers
  • Clojure :foo != Ruby :foo

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  • Rails code, calls Clojure
  • Clojure calls back into Rails
  • But might not be the same runtime
  • might not have the same classpath
  • might not be talking to the same DB
  • might not be the same ruby version

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Lessons Learned

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Complexity is Multiplicative

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Rails Magic

The closer you are to the ‘standard’ environment, the better things work

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  • Rails 3 (ok)
  • using Mongo/Mongoid (not bad)
  • and JRuby (hrm...)
  • and Clojure (OMGWTF)

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Avoid Mixing Paradigms

(In the same process)

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Don’t duplicate Models

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Don’t overestimate the value of code reuse

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Understanding Devise + OmniAuth

>

Writing Oauth2 login in Clojure

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Yes, you will write more code

But you’ll understand it!

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Yes, you will read Clojure source

But it’s simpler!

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The Future

  • Clojure REST API
  • Fat Javascript Client
  • Knockout JS
  • Sammy JS
  • HamlCoffee
  • Clojurescript?

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  • https://github.com/circleci/mongofinil
  • https://github.com/edgecase/dieter

Monday, March 19, 12

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Questions?

@circleci circleci.com

Monday, March 19, 12