Why is rails trying to connect to mysql? - mysql

Question

I have been using mysql in a new rails application, but now I wanted to give mongoDB a try so I installed mongo mapper and mongoid (to use mongo session). The installation seems to be fine because I can create mongo models. But for some reason rails is still trying to connect to mysql: Can't connect to local MySQL server.
This is horrible, because even if I wasn't using mongo, rails shouldn't be trying to connect to mysql for every request. It's throwing that error even for non-existent urls.
What can I do to debug this? I guess I could try removing the mysql gem from the Gemfile and running bundle install. But I still don't like the fact that it's trying to connect even when I'm not using it. Shouldn't it try to connect 'lazily' (ie: only on demand)?
development.rb:
Myapp::Application.configure do
# Settings specified here will take precedence over those in config/application.rb
# In the development environment your application's code is reloaded on
# every request. This slows down response time but is perfect for development
# since you don't have to restart the web server when you make code changes.
config.cache_classes = false
# Log error messages when you accidentally call methods on nil.
config.whiny_nils = true
# Show full error reports and disable caching
config.consider_all_requests_local = true
config.action_controller.perform_caching = false
# Don't care if the mailer can't send
config.action_mailer.raise_delivery_errors = false
# Print deprecation notices to the Rails logger
config.active_support.deprecation = :log
# Only use best-standards-support built into browsers
config.action_dispatch.best_standards_support = :builtin
# Raise exception on mass assignment protection for Active Record models
config.active_record.mass_assignment_sanitizer = :strict
# Log the query plan for queries taking more than this (works
# with SQLite, MySQL, and PostgreSQL)
config.active_record.auto_explain_threshold_in_seconds = 0.5
# Do not compress assets
config.assets.compress = false
# Expands the lines which load the assets
config.assets.debug = true
end
application.rb:
require File.expand_path('../boot', __FILE__)
require 'rails/all'
if defined?(Bundler)
# If you precompile assets before deploying to production, use this line
Bundler.require(*Rails.groups(:assets => %w(development test)))
# If you want your assets lazily compiled in production, use this line
# Bundler.require(:default, :assets, Rails.env)
end
module Myapp
class Application < Rails::Application
# Settings in config/environments/* take precedence over those specified here.
# Application configuration should go into files in config/initializers
# -- all .rb files in that directory are automatically loaded.
# Custom directories with classes and modules you want to be autoloadable.
# config.autoload_paths += %W(#{config.root}/extras)
# Only load the plugins named here, in the order given (default is alphabetical).
# :all can be used as a placeholder for all plugins not explicitly named.
# config.plugins = [ :exception_notification, :ssl_requirement, :all ]
# Activate observers that should always be running.
# config.active_record.observers = :cacher, :garbage_collector, :forum_observer
# Set Time.zone default to the specified zone and make Active Record auto-convert to this zone.
# Run "rake -D time" for a list of tasks for finding time zone names. Default is UTC.
# config.time_zone = 'Central Time (US & Canada)'
# The default locale is :en and all translations from config/locales/*.rb,yml are auto loaded.
# config.i18n.load_path += Dir[Rails.root.join('my', 'locales', '*.{rb,yml}').to_s]
# config.i18n.default_locale = :de
# Configure the default encoding used in templates for Ruby 1.9.
config.encoding = "utf-8"
# Configure sensitive parameters which will be filtered from the log file.
config.filter_parameters += [:password]
# Use SQL instead of Active Record's schema dumper when creating the database.
# This is necessary if your schema can't be completely dumped by the schema dumper,
# like if you have constraints or database-specific column types
# config.active_record.schema_format = :sql
# Enforce whitelist mode for mass assignment.
# This will create an empty whitelist of attributes available for mass-assignment for all models
# in your app. As such, your models will need to explicitly whitelist or blacklist accessible
# parameters by using an attr_accessible or attr_protected declaration.
# config.active_record.whitelist_attributes = true
# Enable the asset pipeline
config.assets.enabled = true
# Version of your assets, change this if you want to expire all your assets
config.assets.version = '1.0'
config.generators do |g|
g.orm :mongo_mapper
end
end
end

Answer 1

When ActiveRecord is part of application, it tries to establish connection to database at startup. If it fails to connect, application won't start.
The problem is here:
require 'rails/all'
This line includes all "usual" rails components, ActiveRecord among them. If you go to its definition, it should look like this (for rails 3.2):
require "rails"
%w(
active_record
action_controller
action_mailer
active_resource
rails/test_unit
sprockets
).each do |framework|
begin
require "#{framework}/railtie"
rescue LoadError
end
end
Take this code, remove active_record line and put it instead your rails/all line. Now, ActiveRecord isn't included and your application will loudly fail when it sees ActiveRecord references in the code, like this:
config.active_record.mass_assignment_sanitizer = :strict
You need to remove these too. You don't need to delete database.yml, but you probably should, since it has no meaning now.

Answer 2

You need delete the line where you configure activerecord :
# Raise exception on mass assignment protection for Active Record models
config.active_record.mass_assignment_sanitizer = :strict
# Log the query plan for queries taking more than this (works
# with SQLite, MySQL, and PostgreSQL)
config.active_record.auto_explain_threshold_in_seconds = 0.5

Answer 3

i presume you've checked your database.yml to make sure nothing is looking for adapter: mysql?
Also if you've left mysql in your Gemfile then the mysql gem will bomb out as it can't do it's part and therefore has to fail as a dependency. Remove it + rerun.