Ork

Ork is a small Ruby modeling layer for Riak database, inspired by Ohm.

Dependencies

ork requires Ruby 1.9 or later and the riak-client gem to connect to Riak.

Install dependencies using dep is easy as run:

dep install

Installation

Install Riak with your package manager:

$ brew install riak

Or download it from Riak's download page

Once you have it installed, you can execute riak start and it will run on localhost:8098 by default.

If you don't have Ork, try this:

$ gem install ork

Getting started

Ork helps you to focus your energy on modeling and designing the object collaborations without worry about how Riak works. Take a look at the example below:

Example

class Post
  include Ork::Document

  attribute :title
  attribute :rating, default: 4

  index :rating
  unique :title
end

class Comment
  include Ork::Document

  attribute :text
  reference :post, :Post
end

It also gives you some helpful class methods:

Class Method	Description	Example (ruby)
bucket	Riak::Bucket The bucket assigned to this class	#<Riak::Bucket {post}>
bucket_name	String The bucket name	"post"
attributes	Array Attributes declared	[:title, :rating]
indices	Array Indices declared	[:rating]
uniques	Array Unique indices declared	[:title]
embedding	Array Embedded attributes declared	[:post]
defaults	Hash Defaults for attributes	{:rating=>4}

And for instance methods it defines:

Instance Method	Description
new?	Bool Answer if its a new instance or not.
embeddable?	Bool Answer if its an embeddable object or not.
update(attr)	Bool Update model attributes and save it.
update_attributes(attr)	Array Update model attributes.
update_embedded_attributes(attr)	Array Update embedded model attributes.
reload	<class> Preload all the attributes from Riak.
save	Bool Persist document.
delete	Bool Delete the document from Riak.

Modeling

Embeddable objects are those with include Ork::Embeddable and they can not be saved without a parent.

Core behaviour of Ork::Model.

attribute

An attribute is just any value that can be stored. It is composed of a :name and an optional hash.

attribute :rating, default: 4

Options

• default: nil set to the attribute a value by default.

• accessors: [:reader, :writer] defines which accessors will be defined

  • :reader a.k.a attr_reader, create a method to read the value.
  • :writer a.k.a attr_writer, create a method to write the value.
  • :question create a question method. Perfect for bool attributes.

reference

It's a special kind of attribute that references another model. Internally, Ork will keep a pointer to the model (its ID), but you get accessors that give you real instances. You can think of it as the model containing the foreign key to another model.

reference :user, :User

referenced

Provides an accessor to search for one model that reference the current model.

referenced :comment, :Comment

collection

It's a special kind of attribute that references another models. Internally, Ork will keep a an array of ids to the models, but you get accessors that give you real instances.

It won't make a query to retrieve all models taht reference the current model. This is something that works well on relational databases but is not recomended for document oriented databases like Riak.

collection :comments, :Comment

embed

Only accepts embeddable objects.

It's a special kind of attribute that embeds another model. Internally, Ork will keep the object as an attribute, but you get accessors that give you real instances.

embed :comment, :Comment

embed_collection

Only accepts embeddable objects.

Provides an accessor for all models that are embedded into the current model. It also provides a method for adding objects to this collection.

embed_collection :comments, :Comment

# It provides
def add_comments(a_comment)
  # code
end

embedded

Only for embeddable objects.

Provides an accessor to the object that embeds the current model.

embedded :post, :Post

index

Create an index for the previously defined attribute.

index :rating

unique

Create a unique index for the previously defined attribute.

unique :title

Pagination

Pagination is a key feature introduced in Riak 1.4 and it is supported as well!

Ork will return the enumerable Ork::ResultSet object which stores the keys and also the resulting objects. The keys are immediately loaded, but the objects will be lazy loaded.

Given it uses the same API than riak_client let's jump into the examples.

resultset = Post.find(:age, 19, max_results: 3)
# => #<Ork::ResultSet:{:max_results=>3} ['object_key_1', 'object_key_2', 'object_key_3']>

resultset.keys
# => ['object_key_1', 'object_key_2', 'object_key_3']

resultset.all
# => [#<Post:1 ...>, #<Post:2 ...>, #<Post:3 ...>]

##
# Advance to next page
##

resultset.has_next_page?
# => true

next_resultset = resultset.next_page
# => #<Ork::ResultSet:{:max_results=>3, :continuation=>'a_continuation_string'}
#    ['object_key_4', 'object_key_5']>

next_resultset.has_next_page?
# => false

next_resultset.next_page
# => raises Ork::NoNextPage: There is no next page

##
# Skip pages and start from a continuation
##

resultset2 = Post.find(:age, 19, max_results: 3, continuation: 'a_continuation_string')
# => #<Ork::ResultSet:{:max_results=>3, :continuation=>'a_continuation_string'}
#    ['object_key_4', 'object_key_5']>

resultset2 == resultset.next_page
# => true

Validations

As you can see, there is no reference to validations in this document and I'm aware of that! The validation logic for nested embedded objects makes the code more complex than I want. Given that I want to keep this gem as simple as I can, I decided to avoid object validation logic here and promote the use of other gems.

There are good implementations for object validation like hatch or scrivener which they do a great job! If you don't know them, you should take a look, but remember that you are free to use your prefered gem or even your own method!

Just remember to check if an object is valid before you save it.

Ork vs Ripple

Tools

• rekon - A visual browser for riak, built as a riak app.