Phusion Passenger 发布 4.0 的第二个 RC 版本，我们知道很多用户期待 4.0 正式版很久了，但没版本，4.0 是一个包含很多改进的版本，因此我们必须进行充分的测试。

Phusion Passenger，原名 mod_rails ，是一个旨在从Apache和Nginx网页服务器上更便捷的部署Ruby on Rails项目的Apache模块。

与 RC1 版本相比，RC2 主要的改变有：

• The Nginx version now supports the passenger_app_root configuration option.
• The Enterprise memory limiting feature has been extended to work with non-Ruby applications as well.
• Application processes that have been killed are now automatically detected within 5 seconds. Previously Phusion Passenger needed to send a request to the process before detecting that it’s gone. This change means that when you kill a process by sending it a signal, Phusion Passenger will automatically respawn it within 5 seconds (provided that the process limit settings allow respawning).
• Phusion Passenger Standalone’s HTTP client body limit has been raised from 50 MB to 1 GB.
• Python 3 support has been added.
• The build system has been made compatible with JRuby and Ruby 2.0. This does not mean that Phusion Passenger works on Ruby 2.0; please read on for more about this subject.
• The installers now print a lot more information about detected system settings so that the user can see whether something has been wrongly detected.
• Some performance optimizations. These involve further extending the zero-copy architecture, and the use of hash table maps instead of binary tree maps.
• Many potential crasher and freezer bugs have been fixed.
• Error diagnostics have been further improved.
• Many documentation improvements.