Reuven Lerner's presentation from Open Ruby Day in Herzliya, Israel on June 27th, 2010. I covered a few tools that are not part of Rails, but which help you with deployment,

1. Rails-related tools
Reuven M. Lerner
Hi-Tech College
June 27th, 2010

2. You shipped!
• Your Web application works
• Everyone thinks that you’re a genius
• Your new application is revolutionary
• Too bad your parents still don’t know quite
what you do for a living

3. Just a few tasks remain
• Find bottlenecks and optimize code
• Find code problems (“smells”), and refactor
• Learn about (and fix) bugs ASAP
• Handle all of this without breaking a sweat

4. Rails can’t help you
• Rails helps you during development
• But it doesn’t try to solve all problems
• There are lots of add-ons that work with
Rails, which make life much easier
• This talk is about those tools

5. • Deployment tool for Rails applications
• Has been around for several years
• “capify” in the root Rails directory
• Creates small “Capfile” in root
• Creates config/deploy.rb

6. What does it do?
• Run “cap deploy” on development machine
• Capistrano:
• Gets latest version from Git/SVN/CVS
• Installs latest version in a new directory
on production server(s)
• Makes a “current” symlink to new dir

7. So what?
• Push to any number of servers
• Keep around old versions, just in case
• Always retrieve from version control
• Add new recipes for your own needs
• Adding/removing servers becomes trivial

8. Deployment directory
reuven@lerner:/var/www/www.modelingcommons.org/www$ ls -l
total 12
lrwxrwxrwx 1 deploy deploy 60 2010-06-25 17:33 current -
> /var/www/www.modelingcommons.org/www/releases/
20100625143221
drwxrwxr-x 95 deploy deploy 4096 2010-06-25 17:32 releases
drwxrwxr-x 6 deploy deploy 4096 2009-05-22 11:02 shared

9. Releases directory
drwxrwxr-x 17 deploy deploy 4096 2010-06-24 17:37 20100624143611
drwxrwxr-x 17 deploy deploy 4096 2010-06-24 18:09 20100624150829
drwxrwxr-x 17 deploy deploy 4096 2010-06-25 10:45 20100625074334
drwxrwxr-x 17 deploy deploy 4096 2010-06-25 11:07 20100625080541
drwxrwxr-x 17 deploy deploy 4096 2010-06-25 16:01 20100625130006
drwxrwxr-x 17 deploy deploy 4096 2010-06-25 16:38 20100625133723
drwxrwxr-x 17 deploy deploy 4096 2010-06-25 16:48 20100625134648
drwxrwxr-x 17 deploy deploy 4096 2010-06-25 17:09 20100625140815
drwxrwxr-x 17 deploy deploy 4096 2010-06-25 17:33 20100625143221

10. A simple recipe
namespace :rake do
desc "Generate a sitemap on a remote server."
task :generate_sitemap do
run("cd #{deploy_to}/current; /usr/bin/rake
sitemap:generate RAILS_ENV=production")
end
end

11. My favorite feature
cap deploy:rollback
• It takes only a moment, because it’s just
rewriting a symlink
• Unnecessary if you never make mistakes

12. Check your errors
• “Exception notifier” plugin was popular for
many years
• Free plugin that sends e-mail on 500 errors

13. • You can try it at hoptoadapp.com
• Free version is good enough for many of
my needs
• Get e-mail exception information
• Also get a Web-based interface
• Mark bugs as having been resolved

16. Can’t you just use logs?
• Yes, but this is more convenient
• “Similar errors” functionality is useful
• Integration with GitHub, Lighthouse
• Reset bug counts when you deploy
• Besides, I like smiling frogs

18. Check your code
• Your code can always use improvement
• Metacognition, reflection assist learning
• Pair programming is good for this
• Not appropriate for everyone
• Get it from a computer, if not a person
• At least you can turn the computer off

19. Code-checking tools
• Ruby has a large (and growing number) of
tools that examine your code
• Many of these are combined in the
metric_fu gem
• Gives you a good sense of the quality of
your code
• If you disagree, no one has to know!

21. metric_fu includes
• Churn — which files were changed the most in version control
• Flay — looks for potential duplication across files
• Flog — measures code complexity
• Rcov — code coverage from your tests
• Reek — looks for “code smells”
• Roodi — looks for design issues
• Saikuro — looks at cyclomatic complexity
• Rails best practices — looks for common Rails problems

22. Reek: Code smells
• Duplication
• Uncommunicative names
• Control couple
• Nested iterators
• Feature envy
• Simulated polymorphism

24. What if you disagree?
• Ignore Reek
• Or think about it again
• Or change the configuration
• Or e-mail Kevin Rutherford
• (Don’t just say, “What a stupid program.”)

25. *****

26. Rails best practices
• New in metric_fu
• Based on a presentation at a Shanghai Ruby
discussion
• http://github.com/flyerhzm/
rails_best_practices
• Helps to keep bad practices in check

27. Typical suggestions
• Move code from view into controller
• Move code from controller into model
• Law of demeter (long.chain.of.method.calls)
• Use before_filter
• Add database index
• Move finder to named scope

28. *****

29. Check your
performance
• Simple benchmarks can be put in code
• I put all sorts of comments in views, logs
• But that implies you know where to look!
• Quick, what are the 5 slowest methods in
your application?
• How many people are affected by them?

30. One option: RPM
• New Relic RPM monitors performance
• Your app sends info to it every so often
• New Relic makes aggregate data available
• Free version is often good enough
• Paid versions are worthwhile if your
business depends on the app!

35. Summary
• Rails is great for developing Web apps
• But there is a whole ecosystem of tools
that can help you to improve your apps
even further
• Many of them are free!
• New ones emerge every month

36. Thanks!
• Israel.rb (Google group)
• Ruby, Rails courses right here!
• Call me: 054-496-8405
• E-mail me: reuven@lerner.co.il
• Interrupt me: reuvenlerner (Skype/AIM)