如果 config.cache_classes = true，Rails 找不到模块答案

【问题标题】：Rails can't find the module, if config.cache_classes = true如果 config.cache_classes = true，Rails 找不到模块
【发布时间】：2012-12-08 23:13:54
【问题描述】：

我有一个 gem，它通过 routes.rb 和 Gemfile 作为引擎安装在我的 rails 应用程序中。以下是重要的部分：

应用的Gemfile

source 'https://rubygems.org'

gem 'rails', '3.2.9'
gem 'mysql2'


group :assets do
  gem 'sass-rails'
  gem 'coffee-rails'
end
gem 'jquery-rails'
gem "common_client", path: "../common-client"

应用的routes.rb

mount CommonClient::Engine => "", :as => 'shared'

gem 的 routes.rb

get '/register' => 'session#new_registration'

gems 的 SessionController

require 'common_client/session_controller_base'

class SessionController < ApplicationController

  include CommonClient::SessionControllerBase
end

gems 的 SessionControllerBase

module CommonClient

  module SessionControllerBase

  def new_registration
      #some code goes here
  end
end

这在开发中工作得很好，rails 能够在访问者点击/register 路由时找到CommonClient::SessionController 并执行new_registration 操作。但在生产环境中，rails 无法找到 CommonClient::SessionController 并生成以下错误：

$ RAILS_ENV=production rails s
=> Booting WEBrick
=> Rails 3.2.9 application starting in production on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
[2012-12-09 03:27:29] INFO  WEBrick 1.3.1
[2012-12-09 03:27:29] INFO  ruby 1.9.3 (2012-10-12) [x86_64-linux]
[2012-12-09 03:27:29] INFO  WEBrick::HTTPServer#start: pid=4248 port=3000
Started GET "/" for 127.0.0.1 at 2012-12-09 03:28:17 +0530
Processing by WelcomeController#index as HTML
Redirected to localhost:3000/register
Filter chain halted as :check_credentials rendered or redirected
Completed 302 Found in 267ms (ActiveRecord: 0.0ms)
Started GET "/register" for 127.0.0.1 at 2012-12-09 03:28:18 +0530

ActionController::RoutingError (uninitialized constant CommonClient::SessionController):
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/inflector/methods.rb:230:in `block in constantize'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/inflector/methods.rb:229:in `each'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/inflector/methods.rb:229:in `constantize'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/routing/route_set.rb:69:in `controller_reference'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/routing/route_set.rb:54:in `controller'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/routing/route_set.rb:32:in `call'
  vendor/bundles/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:68:in `block in call'
  vendor/bundles/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:56:in `each'
  vendor/bundles/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:56:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/routing/route_set.rb:601:in `call'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/engine.rb:479:in `call'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/railtie/configurable.rb:30:in `method_missing'
  vendor/bundles/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:68:in `block in call'
  vendor/bundles/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:56:in `each'
  vendor/bundles/ruby/1.9.1/gems/journey-1.0.4/lib/journey/router.rb:56:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/routing/route_set.rb:601:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/best_standards_support.rb:17:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/etag.rb:23:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/conditionalget.rb:25:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/head.rb:14:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/params_parser.rb:21:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/flash.rb:242:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/session/abstract/id.rb:205:in `context'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/session/abstract/id.rb:200:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/cookies.rb:341:in `call'
  vendor/bundles/ruby/1.9.1/gems/activerecord-3.2.9/lib/active_record/query_cache.rb:64:in `call'
  vendor/bundles/ruby/1.9.1/gems/activerecord-3.2.9/lib/active_record/connection_adapters/abstract/connection_pool.rb:479:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/callbacks.rb:28:in `block in call'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/callbacks.rb:405:in `_run__4296103602150594596__call__1936882885794917979__callbacks'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/callbacks.rb:405:in `__run_callback'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/callbacks.rb:385:in `_run_call_callbacks'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/callbacks.rb:81:in `run_callbacks'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/callbacks.rb:27:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/remote_ip.rb:31:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/debug_exceptions.rb:16:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/show_exceptions.rb:56:in `call'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/rack/logger.rb:32:in `call_app'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/rack/logger.rb:16:in `block in call'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/tagged_logging.rb:22:in `tagged'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/rack/logger.rb:16:in `call'
  vendor/bundles/ruby/1.9.1/gems/actionpack-3.2.9/lib/action_dispatch/middleware/request_id.rb:22:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/methodoverride.rb:21:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/runtime.rb:17:in `call'
  vendor/bundles/ruby/1.9.1/gems/activesupport-3.2.9/lib/active_support/cache/strategy/local_cache.rb:72:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/lock.rb:15:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:136:in `forward'
  vendor/bundles/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:245:in `fetch'
  vendor/bundles/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:185:in `lookup'
  vendor/bundles/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:66:in `call!'
  vendor/bundles/ruby/1.9.1/gems/rack-cache-1.2/lib/rack/cache/context.rb:51:in `call'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/engine.rb:479:in `call'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/application.rb:223:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/content_length.rb:14:in `call'
  vendor/bundles/ruby/1.9.1/gems/railties-3.2.9/lib/rails/rack/log_tailer.rb:17:in `call'
  vendor/bundles/ruby/1.9.1/gems/rack-1.4.1/lib/rack/handler/webrick.rb:59:in `service'
  /home/gaurish/.rvm/rubies/ruby-1.9.3-p286-perf/lib/ruby/1.9.1/webrick/httpserver.rb:138:in `service'
  /home/gaurish/.rvm/rubies/ruby-1.9.3-p286-perf/lib/ruby/1.9.1/webrick/httpserver.rb:94:in `run'
  /home/gaurish/.rvm/rubies/ruby-1.9.3-p286-perf/lib/ruby/1.9.1/webrick/server.rb:191:in `block in start_thread'


^C[2012-12-09 03:42:57] INFO  going to shutdown ...
[2012-12-09 03:42:57] INFO  WEBrick::HTTPServer#start done.
Exiting

现在，这是有趣的部分。当我在production.rb 中禁用代码缓存时，这些错误在生产中消失了，应用程序工作得很好。通过设置

config.cache_classes = false

这一切都让我感到好奇，

为什么 Rails 可以 CommonClient::SessionController 在开发环境中但不能在生产环境中？
设置config.cache_classes = false 如何使它在生产中工作？而且rails可以找到CommonClient::SessionController，这是它之前无法做到的
当 Rails 找到 CommonClient::SessionController 时，除了禁用代码缓存和在每个请求上重新加载所有代码的丑陋黑客之外，我需要做什么？

最后，我已尽力解释，但仍有一些不清楚或需要更多信息。请发表评论。谢谢

【问题讨论】：

也许你必须指定某个地方来加载模块？我不知道具体在哪里
你会碰巧在 github 上的 rails 应用程序或 github 上的虚拟应用程序中拥有这个？
config.cache_classes = true 确保您的应用程序不会在代码更改之间重新编译，因为它在 prod 环境中不是必需的。清除缓存可能会解决此问题。
你使用过 ActiveSupport.on_load(:action_controller) 钩子吗？
common_client/session_controller_base.rb 文件在 lib 文件夹中吗？尝试在 SessionController 上使用 require_dependency "common_client/session_controller_base" 而不是 require

标签： ruby-on-rails ruby-on-rails-3 rubygems ruby-on-rails-3.2 rails-engines

【解决方案1】：

我怀疑这与加载顺序有关。在开发模式下（当 cache_classes 为 false 时），Rails 会在每次请求时加载所有可卸载的类。这发生在框架的其余部分已初始化之后。

相比之下，在生产模式下，所有内容都是一次性加载的，因此您的 CommonClient 可能在 Rails 堆栈的其他部分之前加载，然后被 Rails 加载隐藏。 Valery 关于 ActiveSupport 钩子的建议是一个很好的建议——CommonClient railtie 是什么样的？您可以修改 gem 的 railtie 以在 ActionController 加载后加载控制器，这应该提供更类似于 Rails 的开发模式加载行为的行为。

【讨论】：

【解决方案2】：

尝试像这样更新 routes.rb：

require 'common_client'
mount CommonClient::Engine => '/shared'

【讨论】：