我在排除以下故障并弄清楚为什么我的 Assets 在 slug 编译时无法预编译时遇到了困难……奇怪的是，当我检查实时日志时， Assets 在运行时编译得很好……有什么想法吗？它是否正在尝试连接到数据库？
Preparing app for Rails asset pipeline
Running: rake assets:precompile
rake aborted!
undefined method `match' for nil:NilClass
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid/sessions/mongo_uri.rb:49:in `initialize'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid/sessions/factory.rb:104:in `new'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid/sessions/factory.rb:104:in `parse'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid/sessions/factory.rb:62:in `create_session'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid/sessions/factory.rb:43:in `default'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid/sessions.rb:109:in `default'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid.rb:129:in `default_session'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/mongoid-3.1.4/lib/mongoid/railtie.rb:131:in `block (2 levels) in <class:Railtie>'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:34:in `call'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:34:in `execute_hook'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:43:in `block in run_load_hooks'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:42:in `each'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/lazy_load_hooks.rb:42:in `run_load_hooks'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/application/finisher.rb:59:in `block in <module:Finisher>'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `instance_exec'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/initializable.rb:30:in `run'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/initializable.rb:55:in `block in run_initializers'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `each'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/initializable.rb:54:in `run_initializers'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/application.rb:136:in `initialize!'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/railtie/configurable.rb:30:in `method_missing'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/config/environment.rb:5:in `<top (required)>'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `require'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `block in require'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:236:in `load_dependency'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/activesupport-3.2.13/lib/active_support/dependencies.rb:251:in `require'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/application.rb:103:in `require_environment!'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/railties-3.2.13/lib/rails/application.rb:297:in `block (2 levels) in initialize_tasks'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/sprockets/assets.rake:93:in `block (2 levels) in <top (required)>'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/sprockets/assets.rake:60:in `block (3 levels) in <top (required)>'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/sprockets/assets.rake:23:in `invoke_or_reboot_rake_task'
/tmp/build_27348f41-abb7-46f0-a7ac-6f66bf0feff7/vendor/bundle/ruby/1.9.1/gems/actionpack-3.2.13/lib/sprockets/assets.rake:29:in `block (2 levels) in <top (required)>'
Tasks: TOP => environment
(See full trace by running task with --trace)
最佳答案
检查您的 Assets 预编译在运行期间是否需要访问 ENV 变量。从您的堆栈跟踪中很难判断，但这可能是一个很好的资源:https://devcenter.heroku.com/articles/rails-asset-pipeline
本质上，您可以在 heroku 上启用 user-env-compile labs 功能，以便在预编译期间让您的应用程序实例访问 ENV 变量。
heroku labs:enable user-env-compile -a myapp
更多关于这里的信息:https://devcenter.heroku.com/articles/labs-user-env-compile
关于ruby-on-rails - Heroku 预编译 Assets 失败，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/18972514/