將MySQL連接到Ruby on Rails-ActiveRecord :: ConnectionNotEstablished

Question

我已經將MySQL Workbench與現有數據庫一起安裝，可以使用了。 我安裝了Rails並將我的database.yml文件配置為讀取：

development:
  adapter: mysql2
  encoding: utf8
  database: unibands
  pool: 5
  username: root
  password: 
  host: localhost

但是，當導航到http://localhost:3000上的任何位置時，都會出現以下錯誤： ActiveRecord::ConnectionNotEstablished

終端中的“完整”錯誤為：

Started GET "/pins/index" for 127.0.0.1 at 2013-12-20 19:47:12 +0000

ActiveRecord::ConnectionNotEstablished (ActiveRecord::ConnectionNotEstablished):
  activerecord (4.0.2) lib/active_record/connection_adapters/abstract/connection_pool.rb:546:in `retrieve_connection'
  activerecord (4.0.2) lib/active_record/connection_handling.rb:79:in `retrieve_connection'
  activerecord (4.0.2) lib/active_record/connection_handling.rb:53:in `connection'
  activerecord (4.0.2) lib/active_record/query_cache.rb:51:in `restore_query_cache_settings'
  activerecord (4.0.2) lib/active_record/query_cache.rb:43:in `rescue in call'
  activerecord (4.0.2) lib/active_record/query_cache.rb:32:in `call'
  activerecord (4.0.2) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
  activerecord (4.0.2) lib/active_record/migration.rb:369:in `call'
  actionpack (4.0.2) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
  activesupport (4.0.2) lib/active_support/callbacks.rb:373:in `_run__4325676049139756285__call__callbacks'
  activesupport (4.0.2) lib/active_support/callbacks.rb:80:in `run_callbacks'
  actionpack (4.0.2) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (4.0.2) lib/action_dispatch/middleware/reloader.rb:64:in `call'
  actionpack (4.0.2) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
  actionpack (4.0.2) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
  actionpack (4.0.2) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
  railties (4.0.2) lib/rails/rack/logger.rb:38:in `call_app'
  railties (4.0.2) lib/rails/rack/logger.rb:20:in `block in call'
  activesupport (4.0.2) lib/active_support/tagged_logging.rb:67:in `block in tagged'
  activesupport (4.0.2) lib/active_support/tagged_logging.rb:25:in `tagged'
  activesupport (4.0.2) lib/active_support/tagged_logging.rb:67:in `tagged'
  railties (4.0.2) lib/rails/rack/logger.rb:20:in `call'
  actionpack (4.0.2) lib/action_dispatch/middleware/request_id.rb:21:in `call'
  rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
  rack (1.5.2) lib/rack/runtime.rb:17:in `call'
  activesupport (4.0.2) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  actionpack (4.0.2) lib/action_dispatch/middleware/static.rb:64:in `call'
  rack (1.5.2) lib/rack/sendfile.rb:112:in `call'
  railties (4.0.2) lib/rails/engine.rb:511:in `call'
  railties (4.0.2) lib/rails/application.rb:97:in `call'
  rack (1.5.2) lib/rack/lock.rb:17:in `call'
  rack (1.5.2) lib/rack/content_length.rb:14:in `call'
  rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
  /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
  /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
  /usr/local/rvm/rubies/ruby-1.9.3-p392/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'


  Rendered /usr/local/rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/_source.erb (0.5ms)
  Rendered /usr/local/rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.1ms)
  Rendered /usr/local/rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (0.9ms)
  Rendered /usr/local/rvm/gems/ruby-1.9.3-p392/gems/actionpack-4.0.2/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (14.3ms)

我在裝有Rails 4.0.2的Mac（OS Mavericks）上

如果將連接更改為默認的sqlite3，它將呈現頁面。 因此，這絕對是我的數據庫連接問題。 我是Rails的新手，所以它可能是一個簡單的解決方法，但似乎對我沒有任何幫助。

Answer 1

如果您使用的是MAMP，請在數據庫中添加以下內容。

socket: /Applications/MAMP/tmp/mysql/mysql.sock

默認情況下，MySQL將套接字安裝在/tmp/mysql.soc中，因此請嘗試運行，因為您未運行MAMP

socket: /tmp/mysql/mysql.sock

Answer 2

您可能需要為您的MySQL安裝提供一個套接字。 首先，通過從命令行發出以下命令來找到您的MySQL安裝路徑：

which mysql

然后，將返回的路徑添加為您的database.yml文件中的套接字：

# db/database.yml
development:
  socket: /path/to/mysql/mysql.sock

重新啟動您的Web服務器以重新加載您的配置文件，並且該問題應得到解決。