Valkyrie

Valkyrie is a gem for enabling multiple backends for storage of files and metadata in Samvera.

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Installation

Add this line to your application's Gemfile:

gem 'valkyrie', github: 'samvera-labs/valkyrie'

And then execute:

$ bundle

Configuration

Valkyrie is configured in two places: an initializer that registers the persistence options and a YAML configuration file that sets which options are used by default in which environments.

Sample initializer: config/initializers/valkyrie.rb:

Here is a sample initializer that registers a couple adapters and storage adapters, in each case linking an instance with a short name that can be used to refer to it in your application:

# frozen_string_literal: true
require 'valkyrie'
Rails.application.config.to_prepare do
  Valkyrie::MetadataAdapter.register(
    Valkyrie::Persistence::Postgres::MetadataAdapter,
    :postgres
  )

  Valkyrie::MetadataAdapter.register(
    Valkyrie::Persistence::Memory::MetadataAdapter.new,
    :memory
  )

  Valkyrie::StorageAdapter.register(
    Valkyrie::Storage::Disk.new(base_path: Rails.root.join("tmp", "files")),
    :disk
  )

  Valkyrie::StorageAdapter.register(
    Valkyrie::Storage::Fedora.new(connection: ActiveFedora.fedora.connection),
    :fedora
  )


  Valkyrie::StorageAdapter.register(
    Valkyrie::Storage::Memory.new,
    :memory
  )
end

The initializer registers two Valkyrie::MetadataAdapter instances for storing metadata:

  • :postgres which stores metadata in a PostgreSQL database
  • :memory which stores metadata in an in-memory cache (this cache is not persistent, so it is only appropriate for testing)

Other adapter options include Valkyrie::Persistence::BufferedPersister for buffering in memory before bulk updating another persister, Valkyrie::Persistence::CompositePersister for storing in more than one adapter at once, and Valkyrie::Persistence::Solr for storing in Solr.

The initializer also registers three Valkyrie::StorageAdapter instances for storing files:

  • :disk which stores files on disk
  • :fedora which stores files in Fedora
  • :memory which stores files in an in-memory cache (again, not persistent, so this is only appropriate for testing)

Sample configuration: config/valkyrie.yml:

A sample configuration file that configures your application to use different adapters:

development:
  adapter: postgres
  storage_adapter: disk

test:
  adapter: memory
  storage_adapter: memory

production:
  adapter: postgres
  storage_adapter: fedora

For each environment, you must set two values:

  • adapter is the store where Valkyrie will put the metadata
  • storage_adapter is the store where Valkyrie will put the files

The values are the short names used in your initializer.

Usage

Define a Custom Work

Define a custom work class:

# frozen_string_literal: true
class MyModel < Valkyrie::Resource
  include Valkyrie::Resource::AccessControls
  attribute :id, Valkyrie::Types::ID.optional  # Optional to allow auto-generation of IDs
  attribute :title, Valkyrie::Types::Set       # Sets are unordered
  attribute :authors, Valkyrie::Types::Array   # Arrays are ordered
end

Work Types Generator

To create a custom Valkyrie model in your application, you can use the Rails generator. For example, to generate a model named FooBar with an unordered title field and an ordered member_ids field:

rails generate valkyrie:model FooBar title member_ids:array

You can namespace your model class by including a slash in the model name:

rails generate valkyrie:model Foo/Bar title member_ids:array

Read and Write Data

# create an object
object1 = MyModel.new title: 'My Cool Object', authors: ['Jones, Alice', 'Smith, Bob']
object1 = Persister.save(model: object1)

# load an object from the database
object2 = QueryService.find_by(id: object1.id)

# load all objects
objects = QueryService.find_all

# load all MyModel objects
Valkyrie.config..query_service.find_all_of_model(model: MyModel)

Installing a Development environment

See the parent app README for instructions on setting up a development environment. To run the test suite: 1. Start Solr and Fedora servers for testing with rake server:test in the parent app 1. Run the gem's RSpec test suite with cd valkyrie && rspec spec

License

Valkyrie is available under the Apache 2.0 license.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/samvera-labs/valkyrie/.