无法在Ruby on Rails中连接到MySQL

Question

I have ran gem install mysql2, added the lib file to the bin folder as it say and the mysql2 is in the gem file. What is wrong?

# 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

It looks like an access control issue due to your PRIVILEGES settings. Remember that localhost is a special case not covered by % when granting rights as it will connect over the local UNIX socket and not the port 3306 TCP socket.

You should check that you can connect from the same machine the app is running on using the mysql command-line tool:

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

You should get the same error as the Mysql2 driver at this point.

Generally this is fixed by updating your grants:

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