PostgreSQL

About a year ago I posted about installing Postgres 9.0 on my Mac. We’ll since then I lost a hard drive and am just re-installing Postgres now. This time 9.1. Here’s what I did:

1.  Download postgres for Mac

• Don’t sign up for enterprise db crap, the download will start in a sec

2. Install postgres

• This may require reboot to set some syscontrol settings (it did for me)
• I created the “postgres” user with “postgres” as the password (so I could remember it)

3. Start postgres to create the defaults in the data directory

4. Modify Postgres to use “trust” authentication, so we don’t need to supply a password when connecting to the database.

4.1 For each entry, change METHOD “md5″ to “trust” (this should only be done on your developer machine!)

5. Restart postgres to pick up the conf changes

6. Beer time!

This setup requires you to su – postgres whenever you want to restart the database, but for now it’ll work.

Here are some notes from my installation of it on my Dreamhost account:

1) ssh to your host

2) a simple ‘gem install refinerycms’ just hung & I didn’t feel like waiting around so a quick Google search came up with this answer:

In your tmp directory, create a temporary Gemfile with the following contents:

then run ‘bundle’

The bundle command failed for me, even though ‘gem list’ showed it was installed. So I ran ‘gem install bundle –no-rdoc –no-ri’ which installed a newer version & also setup the binary so I could successfully execute ‘bundle’.

3) Next thing to do is delete the temporary Gemfile and cd to your home directory.

4) From your home directory, execute the following (using your desired [sub]domain name):

5) Then, create a new subdomain in Dreamhost via http://panel.dreamhost.com (same as above, I called mine cms.olore.net), click the checkbox for ‘Passenger (Ruby/Python apps only):’ and let it add ‘public’ to the end of your web directory – this will point to the public directory of the rails app that you just created.

Give Dreamhost a minute or two, then hit your site with a browser. You should see the initial screen for RefineryCMS asking you to create a new user.

Possible problems … with solutions!

a) When first accessing your site, you may get a Passenger error about rack versions. You may need to modify Gemfile.lock to use rack 1.2.1. If you make this change, simply ‘touch tmp/restart.txt’ to tell Passenger to restart, then hit the URL in the browser again.

b) When first accessing your home page you may get a 500 error. I resolved this by running ‘RAILS_ENV=production rake db:migrate’ followed by ‘touch tmp/restart.txt’

Good luck!

To get around this problem, in windows explorer, click on the D: (or wherever your CD/DVD is) and then right click on the .exe file and select “Run as administrator”

This solution was next to impossible to find on the Google, so I am hoping this helps someone!

PostgreSQL

1.  Download postgres for Mac

• Don’t sign up for enterprise db crap, the download will start in a sec

2. Install postgres

• This may require reboot to set some syscontrol settings (it did for me)
• I created the “postgres” user with “postgres” as the password (so I could remember it)

3. Add stuff to your ~/.bash_profile

4. Execute the profile

5. Modify Postgres to use “trust” authentication, so we don’t need to supply a password when connecting to the database.

5.1 For each entry, change METHOD “md5″ to “trust” (this should only be done on your developer machine!)

6. Restart postgres to pick up the conf changes

7. Beer time!

All of the above was done solely so I could run some ActiveRecord tests, so here’s how we do that:

SUCCESS!

It’s really a pretty sweet tool. It generates all these reports and you can either ignore them or act on them. Not saying which of those we do… but that’s not important right now.

If you’ve used metric_fu you probably ran into the NaN error. Good ol’ “Not A Number”.
Generally the output looks something like this:

This particular error has cropped up several times for us, each time we do the same google searches, look at the same metric_fu sources, and slowly dissect which tests are causing this problem. Hopefully this post will help expedite debugging this error for you and your friends.

The NaN error is the result of an Infinity/Infinity calculation in metric_fu. How Infinity gets in there in the first place is left as a reader exercise. Ultimately the problem resides in the fact that the scratch/rcov/rcov.txt output file does not contain the expected output. In fact, in our case, it contained a failing test.

At this point, running rcov by itself (outside of metric_fu) would result in expected output – everything worked and there were no failing tests!

So we ran metric_fu again with all tests disabled except for rcov (by editing our rake task).
Metric_fu failed in the exact same place. Great – at least now it is narrowed down (even if it does take a few minutes to run).

Taking a look at the failing test nothing stood out, until we dug a little deeper.
This test class was overriding a cattr_reader with a cattr_accessor so it could change the value for testing.
No big deal, it worked fine when run by itself ….

Turns out that this wasn’t the only test class that was modifying the class variable.
Metric_fu loads up all of the tests (functionals & units) and runs them together.
We had one unit test class that was modifying a class variable (and not setting it back!) and
a functional test class that was making assertion based on the expected default value of that class variable.
We had indirectly made our tests order dependent.

The reason we never saw it in our normal tests was that our functional and unit tests run separately (via rake).

Summary:

1. Look in scratch/rcov/rcov.txt to find a failing test
2. Look for usage of class variables or constants – namely the changing of them (and not setting them back).

Our Solution:

Our solution was to only temporarily change the class variable, and only do it when we need to:

A better solution would be to get rid of the class variables…
Another solution would be to change metric_fu to handle a failing test more gracefully

In the end, we are left with this rule:

Don’t change class variables in tests!

… or better yet …

Don’t use class variables!

Friends don’t let friends use class variables.
Partnership for cattr-free coding.

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!