Rails 5.1.4 未启动并给出错误：JRuby 或 Windows 不支持工作模式退出

Question

我尝试启动 Rails 服务器，但收到以下错误消息，请问如何修复它

C:\Sites\sample_app>rails s
=> Booting Puma
=> Rails 5.1.4 application starting in development
=> Run `rails server -h` for more startup options
  Please add the following to your Gemfile to avoid polling for changes:
    gem 'wdm', '>= 0.1.0' if Gem.win_platform?
  Please add the following to your Gemfile to avoid polling for changes:
    gem 'wdm', '>= 0.1.0' if Gem.win_platform?
ERROR: worker mode not supported on JRuby or Windows
Exiting

Answer 1

根据Puma 的这个问题页面，可以通过注释掉以下行来解决puma.rb：

workers Integer(ENV['WEB_CONCURRENCY'] || 2)