Heroku error - NameError: uninitialized constant PracticeApp::Application::Mongoid

Question

My application works locally but I am having problems trying to push it to Heroku. I am using mLab and Mongoid in my Rails 5 application. When I enter:

git push heroku master

I get the following errors:

r.rb:102:in `load_rake_tasks!': Could not detect rake tasks (LanguagePack::Helpers::RakeRunner::CannotLoadRakefileError)
remote: ensure you can run `$ bundle exec rake -P` against your app
remote: and using the production group of your Gemfile.
remote: rake aborted!
remote: NameError: uninitialized constant PracticeApp::Application::Mongoid
remote: /tmp/build_7a8e6644d3ecbd6336fe612855f87f95/practice_app/config/application.rb:21:in `<class:Application>'
remote: /tmp/build_7a8e6644d3ecbd6336fe612855f87f95/practice_app/config/application.rb:20:in `<module:PracticeApp>'
remote: /tmp/build_7a8e6644d3ecbd6336fe612855f87f95/practice_app/config/application.rb:19:in `<top (required)>'
remote: /tmp/build_7a8e6644d3ecbd6336fe612855f87f95/practice_app/Rakefile:4:in `require_relative'
remote: /tmp/build_7a8e6644d3ecbd6336fe612855f87f95/practice_app/Rakefile:4:in `<top (required)>'

bundle exec rake -P works fine.

Here is my config/application.rb file:

require_relative 'boot'

require "rails"
# Pick the frameworks you want:
require "active_model/railtie"
require "active_job/railtie"
# require "active_record/railtie"
require "action_controller/railtie"
require "action_mailer/railtie"
require "action_view/railtie"
require "action_cable/engine"
require "sprockets/railtie"
require "rails/test_unit/railtie"

# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(*Rails.groups)

module PracticeApp
  class Application < Rails::Application
    Mongoid.load!("./config/mongoid.yml", :production)
  end
end

My rakefile:

require_relative 'config/application'

Rails.application.load_tasks

In case it's needed here's the production part of mongoid.yml:

# mongoid
#
production:
  clients:
    default:
     uri: mongodb://<username>:<password>@ds133340.mlab.com:33340/okclone

     options:
       connect_timeout: 15

Note: I put in my actual username and password in the uri above.

And my gemfile, in case it's related:

source 'https://rubygems.org'

gem 'rails',        '5.0.1'
gem 'puma',         '3.4.0'
gem 'sass-rails',   '5.0.6'
gem 'uglifier',     '3.0.0'
gem 'coffee-rails', '4.2.1'
gem 'jquery-rails', '4.1.1'
gem 'turbolinks',   '5.0.1'
gem 'jbuilder',     '2.4.1'

group :development, :test do
  gem 'mongoid', '~> 6.1.0'
  gem 'bson_ext'
  gem 'byebug',  '9.0.0', platform: :mri
end

group :development do
  gem 'web-console',           '3.1.1'
  gem 'listen',                '3.0.8'
  gem 'spring',                '1.7.2'
  gem 'spring-watcher-listen', '2.0.0'
end

group :test do
  gem 'rails-controller-testing', '0.1.1'
  gem 'minitest-reporters',       '1.1.9'
  gem 'guard',                    '2.13.0'
  gem 'guard-minitest',           '2.4.4'
end

group :production do
  gem 'rails_12factor'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Edit: I also tried running

heroku config:set PROD_MONGODB = mongodb://dbuser:dbpass@host1:port1,host2:port2/dbname

with my mLab URI added in but that didn't seem to fix the problem.

Answer 1

The problem turned out to be with my gemfile. Because the mongoid and bson gems were only under test and development, they weren't accessible in production. Here is the updated gemfile:

    source 'https://rubygems.org'

    gem 'rails',        '5.0.1'
    gem 'puma',         '3.4.0'
    gem 'sass-rails',   '5.0.6'
    gem 'uglifier',     '3.0.0'
    gem 'coffee-rails', '4.2.1'
    gem 'jquery-rails', '4.1.1'
    gem 'turbolinks',   '5.0.1'
    gem 'jbuilder',     '2.4.1'
    gem 'mongoid', '~> 6.1.0'
    gem 'bson_ext'

    group :development, :test do
      gem 'byebug',  '9.0.0', platform: :mri
    end

    group :development do
      gem 'web-console',           '3.1.1'
      gem 'listen',                '3.0.8'
      gem 'spring',                '1.7.2'
      gem 'spring-watcher-listen', '2.0.0'
    end

    group :test do
      gem 'rails-controller-testing', '0.1.1'
      gem 'minitest-reporters',       '1.1.9'
      gem 'guard',                    '2.13.0'
      gem 'guard-minitest',           '2.4.4'
    end

    group :production do
      gem 'rails_12factor'
    end

    # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
    gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]