即使在成功 rake db:create 之后 Heroku 上也没有数据库连接

Question

我刚刚在 Heroku 上成功运行了 rake db:migrate，这是我第一次部署 Rails 4 应用程序时：

$ heroku run rake db:migrate
Running `rake db:migrate` attached to terminal... up, run.7124
[RailsAdmin] RailsAdmin initialization disabled by default. Pass SKIP_RAILS_ADMIN_INITIALIZER=false if you need it.
Migrating to DeviseCreateUsers (20131223210005)
==  DeviseCreateUsers: migrating ==============================================
-- create_table(:users)
   -> 0.0431s
-- add_index(:users, :email, {:unique=>true})
   -> 0.0093s
-- add_index(:users, :reset_password_token, {:unique=>true})
   -> 0.0185s
==  DeviseCreateUsers: migrated (0.0716s) =====================================

Migrating to AddNameToUsers (20131223210006)
==  AddNameToUsers: migrating =================================================
-- add_column(:users, :name, :string)
   -> 0.0060s
==  AddNameToUsers: migrated (0.0062s) ========================================

Migrating to AddConfirmableToUsers (20131223210008)
==  AddConfirmableToUsers: migrating ==========================================
-- add_column(:users, :confirmation_token, :string)
   -> 0.0030s
-- add_column(:users, :confirmed_at, :datetime)
   -> 0.0016s
-- add_column(:users, :confirmation_sent_at, :datetime)
   -> 0.0018s
-- add_column(:users, :unconfirmed_email, :string)
   -> 0.0016s
==  AddConfirmableToUsers: migrated (0.0085s) =================================

Migrating to RolifyCreateRoles (20131223210011)
==  RolifyCreateRoles: migrating ==============================================
-- create_table(:roles)
   -> 0.0139s
-- create_table(:users_roles, {:id=>false})
   -> 0.0021s
-- add_index(:roles, :name)
   -> 0.0093s
-- add_index(:roles, [:name, :resource_type, :resource_id])
   -> 0.0143s
-- add_index(:users_roles, [:user_id, :role_id])
   -> 0.0095s
==  RolifyCreateRoles: migrated (0.0502s) =====================================

现在，当我转到控制台 - heroku run console 并尝试访问任何模型时，我会收到一条 no database connection 消息。

$ heroku run console
Running `console` attached to terminal... up, run.9633
Loading production environment (Rails 4.0.2)
irb(main):001:0> User
=> User(no database connection)
irb(main):002:0> User
=> User(no database connection)
irb(main):003:0> exit

这是我的 Gemfile 的串联版本（为简洁起见）：

source 'https://rubygems.org'

gem 'rails', '4.0.2'
gem 'sass-rails', '~> 4.0.0'
gem 'cancan'
gem 'devise'
gem 'pg'
gem 'rolify'
gem 'thin'
gem "rails_admin"
gem "friendly_id"

group :development do
  gem 'better_errors'
  gem 'binding_of_caller', :platforms=>[:mri_19, :mri_20, :rbx]
  gem 'quiet_assets'
  gem 'rails_layout'  
  gem 'annotate', :git => 'git://github.com/ctran/annotate_models.git'
  gem 'sextant'
end

group :production do
  gem "rails_12factor"  
end

ruby '2.0.0'

我的database.yml 文件：

# PostgreSQL. Versions 8.2 and up are supported.
#
development:
  adapter:  postgresql
  host:     localhost
  encoding: unicode
  database: mydbname
  pool:     5
  username: myusername
  password:
  template: template0

test:
  adapter:  postgresql
  host:     localhost
  encoding: unicode
  database: my_test_db
  pool:     5
  username: myusername
  password:
  template: template0

production:
  adapter:  postgresql
  host:     localhost
  encoding: unicode
  database: myproductiondb
  pool:     5
  password:
  template: template0

不知道发生了什么。

Answer 1

no database connection 在控制台中并不意味着连接失败。这只是意味着 Rails 还没有连接到数据库（还）可能是因为没有必要。

您可以通过尝试执行查询来查看连接是否有效。比如

User.all

看看它是否会引发任何错误。

为了查看属性，可以在模型上显式触发inspect

User.inspect