how to setup facebook app for heroku site for rails?

Question

My facebook app setup only works on my localhost, but not the heroku site.

I get this error on heroku logs.

    ERROR -- omniauth: (facebook) Authentication failure! no_authorization_code: OmniAuth::Strategies::Facebook::NoAuthorizationCodeError, must pass either a `code` (via URL or by an `fbsr_XXX` signed request cookie)

On facebook settings/advanced, This is the setup I have: Valid OAuth redirect URIs is = http://localhost:3000

On facebook settings/basic, my App Domains is = localhost

and my Site URL is = http://localhost:3000/

my devise.rb

    config.omniauth :facebook, 'somekey', 'somekey', scope: 'email', info_fields: 'email, name'

my omniauth_callbacks_controller.rb

    class OmniauthCallbacksController < Devise::OmniauthCallbacksController 

    def facebook
@user = User.from_omniauth(request.env["omniauth.auth"])

if @user.persisted?
  sign_in_and_redirect @user, :event => :authentication
  set_flash_message(:notice, :success, :kind => "Facebook") if is_navigational_format?
else
  session["devise.facebook_data"] = request.env["omniauth.auth"]
  redirect_to new_user_registration_url
end
  end
  end

My app/models/user.rb

    class User < ActiveRecord::Base
    devise :database_authenticatable, :registerable, :recoverable, :rememberable, :trackable, :validatable, :omniauthable

    def self.from_omniauth(auth)
result = User.where(email: auth.info.email).first

if result
  return result
else
  where(provider: auth.provider, uid: auth.uid).first_or_create do |user|
    user.fullname = auth.info.name
    user.provider = auth.provider
    user.uid = auth.uid
    user.email = auth.info.email
    user.image = auth.info.image
    user.password = Devise.friendly_token[0, 20]
  end
end
 end
 end

In my app/views/devise/sessions/new.html.erb,

<%= link_to "Sign In with Facebook", user_omniauth_authorize_path(:facebook) %>

Answer 1

In your devise.rb, I recommend using ENV variables like so:

config.omniauth :facebook, ENV['FACEBOOK_KEY'], ENV['FACEBOOK_SECRET'], scope: 'email', info_fields: 'email, name'

In development mode, you can use the very helpful Dotenv gem to configure these locally.

Then set these in the Heroku config with:

heroku config:set FACEBOOK_KEY="your_fb_app_key"
heroku config:set FACEBOOK_SECRET="your_fb_app_secret"

Once this is done, your Heroku app should pick up the right Facebook Credentials. Just make sure that your Facebook App is configured to work with your production Heroku URLS in the App Domains settings.