无法在Ruby on Rails中连接到MySQL

Question

我已经运行了gem install mysql2，将lib文件添加到bin文件夹中，并且mysql2在gem文件中。 怎么了？

# MySQL.  Versions 4.1 and 5.0 are recommended.
# 
# Install the MYSQL driver
#   gem install mysql2
#
# Ensure the MySQL gem is defined in your Gemfile
#   gem 'mysql2'
#
# And be sure to use new-style password hashing:
#   http://dev.mysql.com/doc/refman/5.0/en/old-client.html
development:
  adapter: mysql2
  encoding: utf8
  reconnect: false
  database: dealers
  pool: 5
  username: fredric
  password: test
  host: localhost

Mysql2::Error (Access denied for user 'fredric'@'localhost' (using password: YES)):
  mysql2-0.3.11-x86 (mingw32) lib/mysql2/client.rb:44:in `connect'
  mysql2-0.3.11-x86 (mingw32) lib/mysql2/client.rb:44:in `initialize'
  activerecord (3.2.1) lib/active_record/connection_adapters/mysql2_adapter.rb:16:in `new'
  activerecord (3.2.1) lib/active_record/connection_adapters/mysql2_adapter.rb:16:in `mysql2_connection'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:277:in `new_connection'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:287:in `checkout_new_connection'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:235:in `block (2 levels) in checkout'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:230:in `loop'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:230:in `block in checkout'
  C:/Ruby193/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:229:in `checkout'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:95:in `connection'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:374:in `retrieve_connection'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_specification.rb:168:in `retrieve_connection'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_specification.rb:142:in `connection'
  activerecord (3.2.1) lib/active_record/query_cache.rb:67:in `rescue in call'
  activerecord (3.2.1) lib/active_record/query_cache.rb:61:in `call'
  activerecord (3.2.1) lib/active_record/connection_adapters/abstract/connection_pool.rb:443:in `call'
  actionpack (3.2.1) lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
  activesupport (3.2.1) lib/active_support/callbacks.rb:405:in `_run__874471498__call__280582312__callbacks'
  activesupport (3.2.1) lib/active_support/callbacks.rb:405:in `__run_callback'
  activesupport (3.2.1) lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
  activesupport (3.2.1) lib/active_support/callbacks.rb:81:in `run_callbacks'
  actionpack (3.2.1) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  actionpack (3.2.1) lib/action_dispatch/middleware/reloader.rb:65:in `call'
  actionpack (3.2.1) lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
  actionpack (3.2.1) lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
  actionpack (3.2.1) lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
  railties (3.2.1) lib/rails/rack/logger.rb:26:in `call_app'
  railties (3.2.1) lib/rails/rack/logger.rb:16:in `call'
  actionpack (3.2.1) lib/action_dispatch/middleware/request_id.rb:22:in `call'
  rack (1.4.1) lib/rack/methodoverride.rb:21:in `call'
  rack (1.4.1) lib/rack/runtime.rb:17:in `call'
  activesupport (3.2.1) lib/active_support/cache/strategy/local_cache.rb:72:in `call'
  rack (1.4.1) lib/rack/lock.rb:15:in `call'
  actionpack (3.2.1) lib/action_dispatch/middleware/static.rb:53:in `call'
  railties (3.2.1) lib/rails/engine.rb:479:in `call'
  railties (3.2.1) lib/rails/application.rb:220:in `call'
  rack (1.4.1) lib/rack/content_length.rb:14:in `call'
  railties (3.2.1) lib/rails/rack/log_tailer.rb:14:in `call'
  rack (1.4.1) lib/rack/handler/webrick.rb:59:in `service'
  C:/Ruby193/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
  C:/Ruby193/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
  C:/Ruby193/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'


  Rendered C:/Ruby193/lib/ruby/gems/1.9.1/gems/actionpack-3.2.1/lib/action_dispatch/middleware/templates/rescues/_trace.erb (3.0ms)
  Rendered C:/Ruby193/lib/ruby/gems/1.9.1/gems/actionpack-3.2.1/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (39.0ms)
  Rendered C:/Ruby193/lib/ruby/gems/1.9.1/gems/actionpack-3.2.1/lib/action_dispatch/middleware/templates/rescues/diagnostics.erb within rescues/layout (108.0ms)
[2012-02-05 20:30:54] WARN  Could not determine content-length of response body. Set content-length of the response or set Response#chunked = true

Answer 1

由于您的PRIVILEGES设置，它看起来像是一个访问控制问题。 请记住， localhost是授予权限时未被%覆盖的特殊情况，因为它将通过本地UNIX套接字而不是端口3306 TCP套接字进行连接。

您应该检查是否可以使用mysql命令行工具从运行该应用程序的同一台计算机上进行连接：

mysql --user=frederic --password=test dealers

此时你应该得到与Mysql2驱动程序相同的错误。

通常，这可以通过更新您的拨款来解决：

GRANT ALL PRIVILEGES ON dealers.* to `frederic`@`localhost` IDENTIFIED BY 'test'