elasticsearch-model-transactional_callbacks

Elasticsearch::Model::TransactionalCallbacks

The elasticsearch-model works great in simplifying the integration of Ruby classes ("models") with the Elasticsearch search and analytics engine. But, it come short with support for updating the indexed documents asynchronously.

Built-in support for updating the indexed documents comes in the form of Elasticsearch::Model::Callbacks which will updates each related documents individually inside the same thread where the changes were made. Depending on the size of your application, and the size of the changes itself, triggering N number of indexing request to Elasticsearch could amount to nothing, or it could slow down the request-response cycle considerably and render it unusable.

This gem aim to solve this by providing a way to update the index asynchronously via ActiveJob.

Usage

The minimum is to include Elasticsearch::Model::TransactionalCallbacks into any model which could benefit from asynchronous indexing, e.g.

class User < ApplicationRecord
  include Elasticsearch::Model
  include Elasticsearch::Model::TransactionalCallbacks

  index_name 'users'
  document_type 'user'

  mappings do
    # indexes for users
  end
end

But, this will end up trading n+1 on updating index with n+1 on database queries in case your #as_indexed_json pulls data from associated models, e.g.

class Post < ApplicationRecord
  include Elasticsearch::Model
  include Elasticsearch::Model::TransactionalCallbacks

  has_many :taggings, as: :taggable
  has_many :tags, through: :taggings

  index_name 'posts'
  document_type 'post'

  mappings dynamic: false do
    indexes :subject, type: 'text', analyzer: 'english'
    indexes :tags, type: 'keyword'
  end

  def as_indexed_json(_options = {})
    {
      subject: subject,
      tags: tags.map(&:key) # FIXME: this triggers n+1 queries
    }
  end
end

to get around this, you can define a scope called preload_for_index like so:

class Post < ApplicationRecord
  # ...snip...
  scope :preload_for_import, -> { preload(:tags) }
  # ...snip...
end

and it will be automatically called by the library.

Compatibility

This library is compatible and tested with Elasticsearch 5. Some works might be needed to make it works with Elasticsearch 6.

Installation

Add this line to your application's Gemfile:

gem 'elasticsearch-model-transactional_callbacks'

And then execute:

$ bundle

Or install it yourself as:

$ gem install elasticsearch-model-transactional_callbacks

Contributing

Any and all kind of help are welcomed! Especially interested in:

• sample use cases which are not yet supported,
• compatibility with elasticsearch 6.0

feel free to file an issue/PR with sample mapping!

License

The gem is available as open source under the terms of the MIT License.