How to make Guacamole

This is my talk about the guacamole gem I gave at the local Ruby user group in Cologne. Guacamole is an ODM for ArangoDB. The talk is a general introduction to the gem and focuses on the design process and tooling. A short introduction into data source patterns is also present.

Hope you like it.

Transcript

1. Implement a Data Source Pattern for a Multi-Model NoSQL database or How to make Guacamole 16.4.2014 / cologne.rb / @mixxt Dirk Breuer / @railsbros_dirk
2. Data Source Pattern Architectural patterns which drive the way in which the domain logic talks to the database. – Martin Fowler
3. • Active Record • Data Mapper
 • Table Data Gateway • Row Data Gateway • …
4. NoSQL Not ACID compliant Big Data Distributed Web Scale ROFL Scale CAP Documents Flexible High Availability
5. NoSQL Databases • „Not only SQL“ • Not one definition • Sometimes just a marketing buzz-fuzz
6. Classifications • Document-based • Key-Value stores • Graph-based • Column stores • Time series Aggregate-based }
7. Multi-Model Combine more than one approach within one database system
8. Guacamole Source: https://en.wikipedia.org/wiki/File:Guacamole.jpg A dip consisting at least of ripe avocados and salt
9. …and…
10. gem 'guacamole' An ODM for ArangoDB to be used with Rails and other Ruby frameworks* Object Document Mapper *which is not yet finished
11. • Open-Source NoSQL database • Multi-Model • Document-based • Graph-based
12. 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.
14. Before you start
15. Patterns of Enterprise Application Architecture
16. Ingredients
17. 1 Design Goal 1 Data Source Pattern 3 Supporting Libraries 1 Database driver 1 solid Test-Suite 1 Documentation
18. 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
19. Data Source Pattern
20. Data Mapper It’s a Nein! – Doch! – Ohhhh!
21. + 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
22. Supporting Libraries
23. spec.add_dependency 'ashikawa-core' spec.add_dependency 'virtus' spec.add_dependency 'activemodel' spec.add_dependency 'hamster' spec.add_dependency 'activesupport'
24. Implementation
25. Just some bits and pieces…
26. The Model class Post include Guacamole::Model ! attribute :title, String attribute :body, String attribute :comments, Array[Comment] attribute :user, User end
27. The Collection (a.k.a. The Mapper) class PostsCollection include Guacamole::Collection ! map do embeds :comments references :user end end
28. ActiveRecord equivalent class Post < ActiveRecord belongs_to :user has_many :comments end
29. Retrieving Data # Get a user by email UsersCollection.by_example(email: "p.pie@cupcakes.com")
30. Identity Map
31. „Ensures that each object gets loaded only once by keeping every loaded object in a map. Looks up objects using the map when referring to them.“ – Martin Fowler
32. • Not a Cache! • Every session needs its own, fresh instance • Should be suited for concurrency (you know, just in case)
33. module Guacamole class IdentityMap class << self def store(object) @_map = _map.put(key_for(object), object) object end ! def retrieve(klass, key) _map.get key_for(klass, key) end ! def _map @_map ||= Hamster.hash end end end end
34. Lazy Loading
35. Post#user #<User> Proxy UsersCollection.by_key(post_document[:user_key])
36. Active Model compliance
37. • 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
38. Caveats
39. rom-rb/devtools
42. Virtus and Circular Dependencies
44. 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
45. Next Steps
46. Support for Arango Query Language (AQL)
47. Support for Transactions
48. Support the Graph API
49. https://github.com/triAGENS/guacamole Get a Nacho and dip in
50. http://tfcl.de/ http://geekstammtisch.de/ https://github.com/railsbros-dirk Thanks