将 rails 应用程序从 3 升级到 4 时出现 Gem 错误，无法运行 rails s答案

【问题标题】：Gem errors when upgrading rails app from 3 to 4, unable to run rails s将 rails 应用程序从 3 升级到 4 时出现 Gem 错误，无法运行 rails s
【发布时间】：2015-09-06 16:22:17
【问题描述】：

我继承了一个我认为是用 rails 3 编写的 rails 应用程序。我现在正在运行 rails 4.2.3。当我尝试在本地（rails s）运行应用程序时，我收到了许多与活动记录和初始化程序相关的错误。我已经单独搜索了这些错误，但到目前为止我所做的一切都没有奏效。

我已添加此处提到的受保护属性 gem https://github.com/rails/protected_attributes/issues/5

我将 gem 文件升级为使用 rails 4

我已经使用 bundle upgrade 升级了 gems。没运气。

我已向原始开发人员发送了一条消息，但他不知道为什么会发生这种情况。

我需要做什么才能让这个应用程序在本地运行而不会出错？

这是我在终端中运行 rails s 时遇到的错误：

Astrids-MacBook-Air% rails s
=> Booting WEBrick
=> Rails 4.2.3 application starting in development on http://localhost:3000
=> Run `rails server -h` for more startup options
=> Ctrl-C to shutdown server
config.eager_load is set to nil. Please update your config/environments/*.rb files accordingly:

  * development - set it to false
  * test - set it to false (unless you use a tool that preloads your test environment)
  * production - set it to true

Exiting
/Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activerecord-4.2.3/lib/active_record/dynamic_matchers.rb:26:in `method_missing': undefined method `auto_explain_threshold_in_seconds=' for ActiveRecord::Base:Class (NoMethodError)
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activerecord-4.2.3/lib/active_record/railtie.rb:108:in `block (3 levels) in <class:Railtie>'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activerecord-4.2.3/lib/active_record/railtie.rb:107:in `each'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activerecord-4.2.3/lib/active_record/railtie.rb:107:in `block (2 levels) in <class:Railtie>'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/lazy_load_hooks.rb:38:in `instance_eval'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/lazy_load_hooks.rb:38:in `execute_hook'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/lazy_load_hooks.rb:28:in `block in on_load'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/lazy_load_hooks.rb:27:in `each'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/lazy_load_hooks.rb:27:in `on_load'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activerecord-4.2.3/lib/active_record/railtie.rb:106:in `block in <class:Railtie>'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/initializable.rb:30:in `instance_exec'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/initializable.rb:30:in `run'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/initializable.rb:55:in `block in run_initializers'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:226:in `block in tsort_each'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:348:in `block (2 levels) in each_strongly_connected_component'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:429:in `each_strongly_connected_component_from'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:347:in `block in each_strongly_connected_component'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:345:in `each'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:345:in `call'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:345:in `each_strongly_connected_component'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:224:in `tsort_each'
  from /Users/Astrid/.rvm/rubies/ruby-2.2.1/lib/ruby/2.2.0/tsort.rb:203:in `tsort_each'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/initializable.rb:54:in `run_initializers'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/application.rb:352:in `initialize!'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/railtie.rb:194:in `public_send'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/railtie.rb:194:in `method_missing'
  from /Users/Astrid/Documents/Development/Handled/ticketsnap_server/config/environment.rb:5:in `<top (required)>'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:274:in `require'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:274:in `block in require'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:240:in `load_dependency'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/activesupport-4.2.3/lib/active_support/dependencies.rb:274:in `require'
  from /Users/Astrid/Documents/Development/Handled/ticketsnap_server/config.ru:3:in `block in <main>'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/builder.rb:55:in `instance_eval'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/builder.rb:55:in `initialize'
  from /Users/Astrid/Documents/Development/Handled/ticketsnap_server/config.ru:in `new'
  from /Users/Astrid/Documents/Development/Handled/ticketsnap_server/config.ru:in `<main>'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/builder.rb:49:in `eval'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/builder.rb:49:in `new_from_string'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/builder.rb:40:in `parse_file'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/server.rb:299:in `build_app_and_options_from_config'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/server.rb:208:in `app'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands/server.rb:61:in `app'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/rack-1.6.4/lib/rack/server.rb:336:in `wrapped_app'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands/server.rb:139:in `log_to_stdout'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands/server.rb:78:in `start'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:80:in `block in server'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:75:in `tap'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:75:in `server'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
  from /Users/Astrid/.rvm/gems/ruby-2.2.1/gems/railties-4.2.3/lib/rails/commands.rb:17:in `<top (required)>'
  from script/rails:6:in `require'
  from script/rails:6:in `<main>'

【问题讨论】：

rails s development 可以工作。
当您将 Rails 更新为 4.x 时，您是否从配置文件中删除了 auto_explain_threshold_in_seconds 设置，就像在 release notes 中提到的那样？
删除了 auto_explain_threshold_in_seconds 解决了我的问题。

标签： ruby-on-rails ruby ruby-on-rails-3 ruby-on-rails-4 activerecord

【解决方案1】：

删除auto_explain_threshold_in_seconds，如发行说明中所述。

【讨论】：