Ruby Versions and Implementations  – David

http://ruby-versions.net/ – David’s home for ruby versions & implementations for learning & historical reference

Ruby version manager – http://rvm.beginrescueend.com – lets you install several ruby versions/implementations and easily switch between (including your own custom compiled version). Suggestion – don’t install as root, even though it is allowed.

Notes on a few of the existing options:

• MacRuby – interacts with Cocoa
• Rubinius – Ruby in Ruby
• JRuby – Ruby on JVM
• REE – optimized – created by Phusion Passenger team
• MagLev – built in object persistence, repository instead of files, smalltalk-ish
• IronRuby – Ruby on .NET
• URABE – ?

rvm allows you to compare performance between versions/implementation:

rvm ruby-1.8.6,ruby1.9.2 benchmark filename.rb

Why does everyone use 1.8 instead of 1.9?

• Same amount of people are using it as last year (like almost no one)
• Rails considerations
• 1.9 is not 100% backwards compatible
• 1.8.7 backported many of the features of 1.9, so people feel safer

Ruby Enterprise Edition has major memory and speed improvements

Highlights of changes between 1.8 & 1.9

• Enumerators
• Method parameters
• Block variable binding & scope
• Syntax changes

Discussion

• “Ruby 1.9 was plenty different enough to be 2.0″ – David
• 1.9.1 is currently the stable supported version and has been for about a year.
• 1.8.6 to 1.8.7 was a big jump – major backporting of 1.9 features into 1.8
• 1.8.7 was a safe harbor for those that wanted 1.9 features but were scared of 1.9
• rails3 + ruby 1.9.1 = segfaults    … works with certain revisions of 1.9.2 HEAD

Enumerator object – 1.9

• mixes in Enumerable
• you write the ‘each’ method
  • borrow from another object (can be lazy)
  • or
  • pass in code block on instantiation (via a yielder)
• once it knows how to ‘each’, it can do select, map, each_cons ….
• 1.8.6 – require ‘enumerator’ – Enumerable::Enumerator
• 1.9.x – no require needed – promoted to top level ‘Enumerator’

side bar: each_cons vs each_slice

Note to self: I need to memorize each/select/map/collect

What methods do I get with Enumerator that I don’t get with Enumerable (Array)?

Enumerator.instance_methods - Array.instance_methods
:with_index, :with_object, :next, :rewind

Method argument semantics
required args can now come after optional args
def m(a, b=1, c)
def m(a, *b, c)
def m((a,b),c)
required arguments get filled first

Block variable scope

• probably the most important/annoying/significant change
• breaks stuff in surprising ways
• but if it does break stuff, you were likely doing something buggy before

Example 1:

a = [1,2,3]
a.each {|x| p x}

x gets value of 3 when you are done

|x| literally assigns x ( |x=…| ), so it becomes available outside the block

Example 2:

a = 1
array.each { a = 2 }

does not change the value of a

• Matz said he wished he had done this from the beginning
• Unifies the parameter syntax between methods & lambas

1.9 Miscellany

• no more String#each
  • “Hello”[0] = “H”  #in 1.8 it returns 72
• new instance_exec is like instance_eval but takes a param to inject

JRuby – ask David about using ArrayList instead of [] in playpoker.rb

The Testing Landscape

Test::Unit is gone in 1.9
Test::Unit::TestCase -> Mini::Test::TestCase
Mini::Test has a new option: refute_match
require ’shoulda’ – makes it more like RSpec without going full RSpec
RSpec is the defacto standard for Behavior-driven testing

Jeremy – wrote ‘context’ and ‘match’
Given/When/Then – cucumber is most popular
“Think in units of features rather than units of code” – Gregory
require ‘could’ – another tool – include feature test right in the same file as tests

Test data

• YAML/CSV – hard to maintain, csv is kinda nice because you can open in spreadsheet program (or rather your testers can)
• model_stubbing  http://github.com/technoweenie/model_stubbing
• Factories is the new hotness
  • FactoryGirl
  • Machinist – http://github.com/notahat/machinist
    • create shams & blueprints
    • “way slower” than fixtures
• mocking/stubbing
  • can extend a class to do it
  • can use OpenStruct to do it require ‘ostrich’
  • Jeremy likes using ‘rr’
  • RSpec has it’s own stubbing
  • flexmock
• Proxies
  • Proxies are like mocks & stubs & real code combined
  • Proxies are the Ken Jennings of mocks & stubs

http://github/dnclabs

- client_side_validations – gem that does client side validation for rails
- takes AR validations – serves them via json – used by jquery.validate

how to kill rails
github.com/michel
bad practices by a few rails developers
Don’t reduce yourself to $20/hr, stick to your price, delivery quality
Communication is important!

Democracy.com
Raimond Garcia
Revolutionize Democracy
Parsed Congress web page – created a prototype on heroku in 48 hours
legal palitical party in spain – “partido de internet”

What’s new in RSpec-2
David Chelimsky
in beta right now
Old rspec won’t work with Rails 3
doesn’t work with rails < 3 (yet)

http://github.com/rspec

$rspec spec
modularized, rspec-core is built on micronaut

Surveyor gem
Mark Yoon
Surveys in your Rails app
write surveys in DSL
exmaple Kitchen Sink survey
dates, ranges, plck any, grids, multiple answers
needs: admin ui, validations in UI, Rails3 support

http://github.com/breakpointer/surveyor

MySQL is awesome

@igrigorik
Don’t believe all the NoSQL hype

http://bit.ly/bgi1Wf

more flexibility in the relational model
em-proxy gem – tcp level proxy
- used to rewrite SQL queries on the fly

Michael Hartl
railstutorial.org
Joy of publishing online
goal – write a source file, publish HTML & PDF with syntax highlighting & linking to other sections
PolyyTeXnic
HTML & PDF stay in sync

Jake Scruggs
@jakescruggs
ActiveMQ & ActiveMessaging
Mostly a Java shop, so not Resque, delayed job
sending messages is easy
pass id’s NOT serialized objects
Tips:
- Tell ActiveMessage to not be greedy
- Namespace your queues
- Name your pollers
- Double Kill – Die Poller Die – script/poller run vs script/poller start

Greg Nelson
foreign assistance

http://bit.ly/RwandaOnRails

Jim Rumsick (Big Tiger)- HashRocket
Improv – Comedy to Coding
Programming is about communication

http://github.com/flipsasser/Persistence-Smoothie

NoSQL means no ACID
Keep what you know – don’t throw out your MySQL

DataMapper is the swiss army knife of ORM
- can point different models to different datastores
- Have a lot of refactoring to do

Sample Store App
- Authentication – keep in Reational DB
- Products – store metadata
- Purchases – keep it in RDB
- Activity Stream – denormalize with key/value store

mongofy – gem for moving data from mysql to mongo

Drawbacks
- DataPortability is lowered
- Lot more moving parts
- Say goodbye to all your fun AR mixins

Scales linearly – increases not only read access, but also write access

A ColumnFamily per query

CassandraObject
- Mostly AR compatible
- In flux
- taking patches

redis is not use for everything because entire dataset used to have to fit into RAM – would have to shard across machines

github – uses redis for routing, can add, remove.modify routes quickly & easily – can determine what server to put new users on, etc

Old – HAProxy sending to mongrels
New – Unicorn – instead of receiving requests, it asks for one using ’select’, pooled, forks similar to passenger

Used 6 or 7 different bg – SQS, DelayedJob
Used Delayed job for 2 years

resque is built on redis, jobs are serialized to json and workers can be in any language http://github.com/defunkt/resque

resque has a plugin API – 15 or so plugins already exist – http://wiki.github.com/defunkt/resque/plugins

has admin interface

github has 35 types of background jobs

Notes: lightning fast talker! Lots of good information though. I’d have a beer with this guy!

get entire object graph in a single query
previously did 35 joins and took 20 minutes to return

comparison between mongo, couch & cassandra
big selling point was dynamic queries – nice happy medium when coming from relational databases
“I don’t want to write any more ****** XML, so goodbye Cassandra”

No universal agreement that a NOSQL solution was the right idea

“Easiest database to install ever (except maybe Redis)”
No schema migrations

Forked MongoMapper -> Monoid
- MongoMapper was very young

Mongoid
- Prefers Embedding Documents
- Atomic Operations by Default, based on attribute changes
- rich criteria api
- master/slave suppor
- simple versioning
- is NOT ActiveRecord (and should be treated as such)
- Features always have performance in mind

mongo – can index in background as of 1.4
regex queries on fields
Denormalization is acceptable, embed as much as possible (no FK constraints)

Hybrid DB model
- Hierarchical Data Stored in MongoDB
- Relational Data stored in MySQL
- Data that required transactions stored in MySQL
- Simple Data in Redis
- Favor suitability over simplicity

It’s ok to use more than one datastore

Working without transactions
- Atomic updates generally cover you
- fairly easy to roll your own optimistic locking
- need to do manual rollback in integration tests
- selenium tests can run in a separate process

in production
- deployed on engine yard cloud / ec2
- 0.5 TB of data
- put mongodb on it’s own utility space
- feed it lots of ram, lots of disk space
- chef scripts easy due to simple installation

http://try.mongodb.com – mini tutorial

MongoDB tries to fit between key-value stores & relational databases

Data as Documents – documents are in BSON (binary json)

mongoDB operates on documents using special syntax

update() takes a query and an update (what to do) .. the update is applied to the results of the query

Embedded documents – i.e. Comments become embedded within Posts
Or you can normalize – Post id within each comment
Decisions to be made on what makes most sense for how you need to access the data

Embedded – fast queries, document always appears with parent

Hash is the object used to represent MongoDB objects

MongoMapper

Very informational, I want to try using this!

2 of the 3 cofounders here in room
Do one thing well – deploy a rails application onto the web
$git push heroku master
let developers use tools to deploy that they are already using
“No step 1″

heroku stacks – let’s you target a version of a vm & libraries that you want to target – linux version, ruby, etc

http://docs.heroku.com/rails3

http://www.scvngr.com

http://www.syphir.com

http://getcloudapp.com

pandastream – cloud based video encoding

Anything can be a cloud service as long as it’s deployed in the same infrastructure – memcached, monogohq, etc

My note: this is probably a sales pitch on RPM, but at least I know that gong in

• Performance is value
• Apdex – how your customers feel about the service they are getting – how satisfied they are
• Awesome “Knuth is my homeboy” image with appropriate quote: “premature optimization is the root of all evil”
• Nice charts to compare metrics vs 24 hours ago, a week ago, a month ago

My note: I was right, and now I am bored…but I am going to go read about solr

How did we get here?
Technical Debt – but there is no bailout program! Good idea if you intend on paying back.

Metrics are a great way to facilitation conversation
It’s ok to ask others how/why the code was written

if its hard to write tests around your code, that’s a smell

output of metrics tools is just text – you can make these metrics tool fail the build !

There’s no substitute for peer review

rcov can fail the build by setting “–failure-threshold n”
- should increase the threshold as your code coverage goes up so that you know when it drops

reek – fail the build by capturing the output
result = %x{reek app lib}
exit 1 unless result.empty?

flog -
flog app  awk ‘NR==4′ | awk ‘{print $1}’
exit 1 if result.gsub(“:”,”").to_i >= 20

metric-fu
wraps tests in pretty pictures

Compare charts to previous sprints – generate conversation

Great presentation materials – cartoony, fun
Good speaker, useful demo