ruby

class SessionsController < ApplicationController
  def new
    @user = User.new
  end

  def create

class AddMetadataToUsers < ActiveRecord::Migration[6.1]
  def change
    add_column :users, :metadata, :jsonb, default: {}, null: false
    add_index :users, :metadata, using: :gin
  end
end

class LikesController < ApplicationController
  before_action :set_post

  def create
    @like = @post.likes.find_or_create_by(user: current_user)

module EventBus
  @subscribers = Hash.new { |h, k| h[k] = [] }

  class << self
    def subscribe(event_class, handler = nil, &block)
      callable = handler || block

class Article < ApplicationRecord
  include PgSearch::Model

  pg_search_scope :full_text_search,
    against: { title: 'A', body: 'B' },
    using: {

class CircuitBreaker
  class CircuitOpenError < StandardError; end

  def initialize(name, redis: Redis.current, failure_threshold: 5, failure_window: 60, cooldown: 30)
    @key = "circuit:#{name}"
    @redis = redis