Docker 组合失败并出现“require”：无法加载此类文件 -- rack/handler/rails (LoadError)答案

【问题标题】：Docker compose up fails with `require': cannot load such file -- rack/handler/rails (LoadError)Docker 组合失败并出现“require”：无法加载此类文件 -- rack/handler/rails (LoadError)
【发布时间】：2016-04-06 12:17:14
【问题描述】：

这是我的 Dockerfile：

FROM rails:4.2.4
MAINTAINER Brena Monteiro <me@monteirobrena.com>
RUN mkdir -p ~/myapp
COPY . ~/myapp
COPY Gemfile ~/myapp/Gemfile
COPY Gemfile ~/myapp/Gemfile.lock
WORKDIR ~/myapp
RUN bundle install
CMD rails s -b 0.0.0.0

还有我的docker-compose.yml：

web:
  build: .
  command: rails s -p 3000 -b '0.0.0.0'
  ports:
    - '3000:8080'
  volumes:
    - .:/Users/monteirobrena/myapp

如果我运行docker run，Docker 会正确启动：

docker run -v ./:/Users/monteirobrena/docker/myapp -p 3000:8080 myapp

但是当我运行docker-compose up 时，我收到了这个错误：

➜  app git:(add-docker) ✗ docker-compose up         
myRecreating app_web_1
myAttaching to app_web_1
web_1 | /usr/local/bundle/gems/rack-1.6.4/lib/rack/handler.rb:78:in `require': cannot load such file -- rack/handler/rails (LoadError)
web_1 |   from /usr/local/bundle/gems/rack-1.6.4/lib/rack/handler.rb:78:in `try_require'
web_1 |   from /usr/local/bundle/gems/rack-1.6.4/lib/rack/handler.rb:16:in `get'
web_1 |   from /usr/local/bundle/gems/rack-1.6.4/lib/rack/server.rb:290:in `server'
web_1 |   from /usr/local/bundle/gems/railties-4.2.3/lib/rails/commands/server.rb:125:in `print_boot_information'
web_1 |   from /usr/local/bundle/gems/railties-4.2.3/lib/rails/commands/server.rb:75:in `start'
web_1 |   from /usr/local/bundle/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:80:in `block in server'
web_1 |   from /usr/local/bundle/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:75:in `tap'
web_1 |   from /usr/local/bundle/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:75:in `server'
web_1 |   from /usr/local/bundle/gems/railties-4.2.3/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
web_1 |   from /usr/local/bundle/gems/railties-4.2.3/lib/rails/commands.rb:17:in `<top (required)>'
web_1 |   from /usr/src/app/bin/rails:9:in `require'
web_1 |   from /usr/src/app/bin/rails:9:in `<top (required)>'
web_1 |   from /usr/local/bundle/gems/spring-1.6.4/lib/spring/client/rails.rb:28:in `load'
web_1 |   from /usr/local/bundle/gems/spring-1.6.4/lib/spring/client/rails.rb:28:in `call'
web_1 |   from /usr/local/bundle/gems/spring-1.6.4/lib/spring/client/command.rb:7:in `call'
web_1 |   from /usr/local/bundle/gems/spring-1.6.4/lib/spring/client.rb:28:in `run'
web_1 |   from /usr/local/bundle/gems/spring-1.6.4/bin/spring:49:in `<top (required)>'
web_1 |   from /usr/local/bundle/gems/spring-1.6.4/lib/spring/binstub.rb:11:in `load'
web_1 |   from /usr/local/bundle/gems/spring-1.6.4/lib/spring/binstub.rb:11:in `<top (required)>'
web_1 |   from /usr/src/app/bin/spring:13:in `require'
web_1 |   from /usr/src/app/bin/spring:13:in `<top (required)>'
web_1 |   from bin/rails:3:in `load'
web_1 |   from bin/rails:3:in `<main>'
web_1 | Exiting
myapp_web_1 exited with code

有什么想法吗？

【问题讨论】：

没有 docker 也能正常工作吗？
是的，没有 Docker 和 docker run 也可以正常工作。

标签： ruby-on-rails docker docker-compose dockerfile

【解决方案1】：

使用bundle exec 启动rails 服务器，如下所示：

 web:
  build: .
  command: bundle exec rails s -p 3000 -b '0.0.0.0'
  ports:
    - '3000:8080'
  volumes:
    - .:/Users/monteirobrena/myapp

【讨论】：

这条线COPY Gemfile ~/myapp/Gemfile.lock不应该是COPY Gemfile.lock ~/myapp/Gemfile.lock吗？
您能否删除 Docker 文件 CMD rails s -b 0.0.0.0 的最后一行并尝试再次运行 docker-compose？
当我更改为bundle exec rails s 时，我收到此错误`require': cannot load such file。
同样没有CMD 行:(
我将您的 Dockerfile 和 docker-compose-yml 文件复制/粘贴到现有项目中。我可以build 和up，您可以将您的Gemfile 添加到您的问题中吗？