Latest version of Building Cloud Castles, given at LRUG in April 2011. A year ago, I was a committed VPS and dedicated-machine deployer. I thought the cloud imposed silly restrictions - how dare you take away my shell account! Whaddya mean I can't save files locally? Since then, I've had some interesting experiences. I've worked on big cloud-deployed systems, and certain large traditionally-deployed systems, and I've seen how a lot of the decisions that you're ... encouraged to make when designing an app to run in the cloud. Most interestingly, I've discovered how those same decisions can make for a much better app regardless of where it'll end up. In this talk, I'll share those architectural patterns with you, and show why they work. Hopefully, I'll convince all of you to build cloud castles -- even if you've got your foundation firmly on the ground.

1. BUILDING
CLOUD
CASTLES
ben scofield / @bscofield / LRUG / 11 April 2011

2. this presentation is a
WORK IN PROGRESS
http://www.flickr.com/photos/natlockwood/1006351276/

4. not just

5. the cloud allows
LIMITED ACCESS

6. FINDING PROBLEMS

7. LOCAL
$ ssh deploy@production.server.com
Linux production.server #1 SMP Sat Dec 5 16:04:55 UTC 2009 i686
To access official Ubuntu documentation, please visit:
http://help.ubuntu.com/
Last login: Fri Jan 28 16:33:49 2011 from local.host
deploy@production:~$ cd /var/log/apache2
deploy@production:/var/log/apache2$ tail error.log
[Sun Jan 23 06:25:02 2011] [notice] Apache/2.2.12 (Ubuntu) Phusion_Passenger...
[Tue Jan 25 15:21:42 2011] [error] [client 118.129.166.97] Invalid URI in ...
[Fri Jan 28 12:01:50 2011] [error] [client 85.132.70.133] client sent HTTP/1...
[Sun Jan 30 06:25:06 2011] [notice] SIGUSR1 received. Doing graceful restart

8. NODE NODE NODE NODE
NODE NODE NODE NODE

9. CLOUD
$ heroku logs --remote production
2011-04-11T01:34:22-07:00 app[web.1]: Rendered text template within layout...
2011-04-11T01:34:22-07:00 app[web.1]: Completed 200 OK in 54ms
2011-04-11T01:34:30-07:00 app[web.3]: Rendered text template within layout...
2011-04-11T01:34:30-07:00 app[web.3]: Completed 200 OK in 111ms (Views:57....
2011-04-11T08:34:42+00:00 heroku[router]: GET devcenter.heroku.com/article...
2011-04-11T01:34:42-07:00 heroku[nginx]: GET /articles/facebook HTTP/1.0 |...
2011-04-11T01:34:42-07:00 app[worker.1]: [Worker(host:railgun64.53370 pid:...
2011-04-11T01:34:42-07:00 app[worker.1]: [Worker(host:railgun64.53370 pid:...

10. http://hoptoadapp.com

11. http://newrelic.com

12. source

13. FIXING PROBLEMS

14. LOCAL
$ ssh deploy@production.server.com
Linux production.server #1 SMP Sat Dec 5 16:04:55 UTC 2009 i686
To access official Ubuntu documentation, please visit:
http://help.ubuntu.com/
Last login: Fri Jan 28 16:33:49 2011 from local.host
deploy@production:~$ cd /var/www/app/current/
deploy@production:/var/www/app/current$ rails console production
Loading production environment (Rails 3.0.3)
>> Article.count
=> 112
>> Article.where(:problem => true).update_attributes(:problem => false)

15. CLOUD
require 'test_helper'
class ArticleTest < ActiveSupport::TestCase
context 'Broken articles' do
setup do
5.times.do { Factory :broken_article }
end
should 'be fixable' do
assert_equal 5, Article.where(:problem => true).count
Article.fix_problem_articles
assert_equal 0, Article.where(:problem => true).count
end
end
end
class Article
def self.fix_problem_articles
where(:problem => true).update_attributes(:problem => false)
end
end

16. the cloud is
UNRELIABLE
locally

17. LOCAL
class Comic < ActiveRecord::Base
has_attached_file :cover, :styles => {
:thumb => "80x120>",
:medium => "300x450>"
}
end
$ cd public/system
$ ls /covers
10/ 12/ 53/ 81/
$ ls /covers/10/
medium/ original/ thumb/
$ ls /covers/10/medium
batman-450.png

18. NODE NODE NODE NODE
NODE NODE NODE NODE

19. EVENTUAL
CONSISTENCY

20. CLOUD
class Comic < ActiveRecord::Base
has_attached_file :cover, :storage => s3,
:s3_credentials => {
:access_key_id => ENV['S3_KEY'],
:secret_access_key => ENV['S3_SECRET']
},
:bucket => 'comicsapp',
:url => ":s3_path_url",
:s3_headers => { 'Expires' => 1.year.from_now.httpdate },
:styles => {
:thumb => "80x120>",
:medium => "300x450>"
}
end

21. SERVER SERVER

22. STORAGE
SERVER SERVER

23. the cloud can be
EXPENSIVE

24. NODE NODE NODE NODE
NODE NODE NODE NODE

25. CACHING
NODE NODE NODE NODE
NODE NODE NODE NODE

26. SERVER

27. CACHING
SERVER

28. the cloud prefers
SMALL APPS

29. NODE NODE NODE NODE
NODE NODE NODE NODE

30. NODE NODE NODE NODE
NODE NODE NODE NODE

31. REST

32. NODE NODE NODE
EXTERNAL
SERVICE
NODE NODE NODE

34. SERVER

35. SERVER SERVER

36. SERVER SERVICE

37. the cloud is
UNRELIABLE
remotely

38. CLOUD
class Searcher
cattr_accessor :index
def self.index
@api ||= IndexTank::Client.new(ENV['INDEXTANK_API_URL'])
@index = @api.indexes 'articles'
end
def self.search(term)
raw = self.index.search(term, :function => 1)
results = raw['results'].to_a
article_ids = results.map {|result| result['docid'] }
unsorted = Article.published.where(:id => article_ids)
results.map { |result|
unsorted.find {|u| u.id.to_i == result['docid'].to_i}
}.compact
end
end

39. EXPECT FAILURE

40. CLOUD
class Searcher
# ...
def self.search(term)
results = begin
raw = self.index.search(term, :function => 1)
raw['results'].to_a
rescue URI::InvalidURIError # An IndexTank error occurred
search_by_sql(term)['results']
end
# ...
end
def self.search_by_sql(term)
{'results' => Article.where(['content ILIKE ?', "%#{term}%"]).
map {|a| {'docid' => a.id}}}
end
end

41. DEFENSIVE CODING

42. the cloud is
ALWAYS CURRENT

43. RAISE YOUR HAND if

44. INFRASTRUCTURE

45. PATTERNS and VIRTUES

46. HUMILITY

47. LAZINESS

48. PARANOIA

49. SOLID
single responsibility principle
liskov substitution principle
interface segregation principle

50. CLOUD PRACTICES
are
BEST PRACTICES

51. THANK YOU!
Ben Scofield / @bscofield
http://benscofield.com
http://speakerrate.com/t/7123