data_snapshots

Simple, flexible data snapshotting for your Rails app.

Run the following command to add data_snapshots to your Gemfile:

bundle add data_snapshots

Once installed, copy and run the migration:

bundle exec rails data_snapshots_engine:install:migrations
bundle exec rails db:migrate

A model snapshot is a collection of methods that run against a model instance. Methods will be passed the instance when the snapshot is generated.

You can register your snapshots in an initializer:

DataSnapshots.configure  do  |c|
  c.register_snapshot name: :user_assignments do |methods|
    methods[:total] = ->(instance) { instance.assignments.count }
    methods[:total_complete] = ->(instance) { instance.assignments.where(complete: true).count }
  end
end

A generic snapshot is a collection of methods that will not be passed a model instance when the snapshot is generated. You can declare a snapshot as generic by passing model: false as an argument when registering the snapshot:

DataSnapshots.configure  do  |c|
  c.register_snapshot name: :totals, model: false do |methods|
    methods[:total_users] = ->() { User.count }
    methods[:total_assignments] = ->() { Assignments.count }
  end
end

Model snapshots can either be generated on the individual instance:

user = User.last
user.generate_snapshot(name: :user_assignments)

Or you can generate them with a collection of records:

DataSnapshots.generate_snapshots(name: :user_assignments, collection: User.all)

Generic snapshots can be created by passing the name of the snapshot to DataSnapshots.generate_snapshot

DataSnapshots.generate_snapshot(name: :total_users)

data_snapshots comes with a <NAME>_snapshots method so its easy to fetch all the snapshots taken against a particular instance:

user.user_assignments_snapshots

You can fetch your generic snapshots by calling DataSnapshots.fetch_snapshots and passing the name of your snapshot:

DataSnapshots.fetch_snapshots(name: :total_users)

This method can also be used to fetch ALL model snapshots with the given name.

Snapshot data is stored as JSON in the database and can be accessed easily:

snapshot.data # => { 'key' => 'value' }

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