Simple change tracking for Rails models. It also works for non-database-backed models with optional change tracking.

app-models-application_record.rb

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

  include ActivityLogger
end

app-models-concerns-activity_logger.rb

module ActivityLogger
  extend ActiveSupport::Concern

  included do
    [["create", "created"], ["update", "updated"], ["destroy", "destroyed"]].each do |meth, action|
      if respond_to?("after_#{meth}")
        send("after_#{meth}", -> { log_activity(action) })
      end
    end
  end

  protected

  def activity_data
    respond_to?(:saved_changes) && saved_changes.any? ? {changes: saved_changes.except("created_at", "updated_at")} : {}
  end

  def activity_attributes
    attributes.slice("id", "name")
  end

  def log_activity(action, data: nil)
    data ||= activity_attributes.merge(activity_data)
    # This assumes Current.user is set in a controller, but it will work without it
    ActiveSupport::Notifications.instrument("activity", {event: "#{action}-#{model_name.singular}", user_id: Current.user&.id, data: data})
  end
end

config-initializers-notifications.rb

ActiveSupport::Notifications.subscribe("activity") do |*args|
  event = ActiveSupport::Notifications::Event.new(*args)
  Rails.logger.info({ activity: event.payload.compact }.to_json)
end