discourse/app/models/view.rb

require 'ipaddr'

class View < ActiveRecord::Base
  belongs_to :parent, polymorphic: true
  belongs_to :user
  validates_presence_of :parent_type, :parent_id, :ip, :viewed_at

  # TODO: This could happen asyncronously
  def self.create_for(parent, ip, user=nil)

    # Only store a view once per day per thing per user per ip
    redis_key = "view:#{parent.class.name}:#{parent.id}:#{Date.today.to_s}"
    if user.present?
      redis_key << ":user-#{user.id}"
    else
      redis_key << ":ip-#{ip}"
    end

    if $redis.setnx(redis_key, "1")
      $redis.expire(redis_key, 1.day.to_i)

      View.transaction do
        View.create(parent: parent, ip: IPAddr.new(ip).to_i, viewed_at: Date.today, user: user)

        # Update the views count in the parent, if it exists.
        if parent.respond_to?(:views)
          parent.class.update_all 'views = views + 1', id: parent.id
        end
      end
    end
  end
end