This is a talk about Guacamole, an ODM for ArangoDB to be used in Rack-based framework and especially Rails. Dirk gave the talk in London at Skills Matter

1. How to make Guacamole
or
Implement a Data Source Pattern for a Multi-Model NoSQL database
11.8.2014Dirk Breuer/ @railsbros_dirk

2. How to make Guacamole
or
Implement a Data Source Pattern for a Multi-Model NoSQL database
11.8.2014Dirk Breuer/ @railsbros_dirk

3. Data Source Pattern
Architectural patterns which drive
the way in which the domain logic
talks to the database.
– Martin Fowler

4. • Active Record
• Data Mapper
• Table Data Gateway
• Row Data Gateway
• …

5. NoSQL
Not ACID compliant
Big Data
Distributed
Web Scale
ROFL Scale
CAP
Documents
Flexible
High Availability

6. NoSQL Databases
• “Not only SQL”
• Not one definition
• Sometimes just a marketing buzz-fuzz

7. Classifications
• Document-based
• Key-Value stores
• Graph-based
• Column stores
• Time series
Aggregate-based}

8. Multi-Model
Combine more than one approach
within one database system

9. Guacamole
Source: https://en.wikipedia.org/wiki/File:Guacamole.jpg
A dip consisting at least of ripe avocados and salt

10. …and…

11. gem 'guacamole'
An ODM for ArangoDB to be used with Rails and any Ruby application
Object Document Mapper

12. • Open-Source NoSQL database
• Multi-Model
• Document-based
• Graph-based

13. Why should I use
ArangoDB in favor of
<any other document store>?
With ArangoDB you can perform joins
over your documents similar
to joins in relational databases.

15. • Powerful query language (AQL)
• REST HTTP interface
• Embedded V8 to allow custom REST interfaces (Foxx)
• Mostly-Memory based with configurable disk synchronization
• Support for Transactions
• Native driver for most languages

17. http://docs.arangodb.org/
Everything
and more

18. Before you start building
your own ODM

19. Patterns of Enterprise Application Architecture

20. Ingredients

21. 1 Design Goal
1 Data Source Pattern
3 📦 Supporting Libraries
1 Database driver
1 solid Test-Suite
1 📦 Documentation

22. Design Goal
• Support building web applications with Ruby on Rails or
other Rack-based frameworks
• Focus on easy integration in Views and the general
workflow
• Reflect the nature of NoSQL in general and ArangoDB in
particular

23. Data Source Pattern

24. Data Mapper
It’s a

25. + Testability is increased
+ Separation of Concern
+ Easier to support database
features like embedded objects
- The average Rails dev is
used to Active Record
- Starting with Data Mapper
requires more effort

26. Supporting Libraries

27. spec.add_dependency 'ashikawa-core'
spec.add_dependency 'virtus'
spec.add_dependency 'activemodel'
spec.add_dependency 'hamster'
spec.add_dependency 'activesupport'

28. Implementation

29. Just some bits and pieces…

30. ActiveRecord example
class Post < ActiveRecord
belongs_to :user
has_many :comments
end

31. The Model™ in Guacamole
class Post
include Guacamole::Model
!
attribute :title, String
attribute :body, String
attribute :comments, Array[Comment]
attribute :user, User
end

32. The Collection™ in Guacamole
class PostsCollection
include Guacamole::Collection
!
map do
embeds :comments
references :user
end
end

33. Retrieving Data
# Get a user by email
UsersCollection.by_example(email: 'p.pie@cupcakes.com')
# => #<User:0x007fca7186fc98>

34. With AQL support
# Get a user by name
UsersCollection.by_aql('FILTER user.name == @name',
name: 'Rainbow Dash')
# => #<User:0x007fca7186fc98>
http://docs.arangodb.org/Aql/README.html
Don’t be scared!

35. CallbacksExternal

36. class SecurePonyCallbacks
include Guacamole::Callbacks
!
# Those will be triggered by the collection
before_create :encrypt_password
!
def encrypt_password
object.encrypted_password = BCrypt::Password.create(object.password)
end
end

37. class SecurePony
include Guacamole::Model
!
callbacks :secure_pony_callbacks
!
attribute :encrypted_password, String
!
# define a virtual attribute
attr_accessor :password
end

38. ActiveModel::Callbacks
powered by

39. Active Model compliance

40. • Really useful, not only for Rails
• A lot of Gems build on top of Active Model
• A lot of useful features (i.e. Validations)
• Not related to the Active Record pattern

41. Development with Metrics

42. Check your Code for
• Complexity
• Duplication / Similarity
• Style
• Smells
• Sufficient documentation

45. Caveats
Virtus and Circular Dependencies

47. class Author
extend ActiveSupport::Autoload
include Guacamole::Model
!
autoload :Book, 'models/book'
!
attribute :name, String
attribute :books, Array[Book]
end
class Book
extend ActiveSupport::Autoload
include Guacamole::Model
!
autoload :Author, 'models/author'
!
attribute :title, String
attribute :author, Author
end
This is not
very Ruby

48. Next Steps

49. A DSL to create AQL-Queries

50. Support for Transactions

51. Support the Graph API
Up Next

52. http://guacamolegem.org
Get a Nacho
and dip in

53. Come to us we have
cookies animated GIFs.

55. Sneak Peak

56. 2014.eurucamp.org/podcast

57. https://www.arangodb.orghttp://guacamolegem.org
@railsbros_dirk
Thanks