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Phusion Passenger 4.0 Release Candidate 6

By Hongli Lai on April 9th, 2013

Phusion Passenger turns Apache and Nginx into a full-featured application server for Ruby and Python web apps. It has a strong focus on ease of use, stability and performance. Phusion Passenger is built on top of tried-and-true, battle-hardened Unix technologies, yet at the same time introduces innovations not found in most traditional Unix servers. Since mid-2012, it aims to be the ultimate polyglot application server.

Today we are pleased to announce Release Candidate 6 of Phusion Passenger 4.0. The 4.x series is a huge improvement over the 3.x series: during the development of 4.0, we’ve introduced a myriad of changes which we’ve covered in past beta preview articles:

Release Candidate 5 was a private interim release for Phusion Passenger Enterprise customers only.

Changes in 4.0 RC 5 and RC 6

The most important changes in RC 5 and RC 6 are as follows:

  • The default config snippet for Apache has changed! It must now contain a
    PassengerDefaultRuby option. The installer has been updated to output
    this option. The PassengerRuby option still exists, but it’s only used
    for configuring different Ruby interpreters in different contexts. Please
    refer to the manual for more information.
  • We now provide GPG digital signatures for all file releases by Phusion.
    More information can be found in the manual.
  • WebSocket support on Nginx. Requires Nginx >= 1.3.15.
  • passenger-status now displays process memory usage and time when it
    was last used. The latter fixes issue #853.
  • Exceptions in Rack application objects are now caught to prevent
    application processes from exiting.
  • The passenger-config tool now supports the --ruby-command argument,
    which helps the user with figuring out the correct Ruby command to use
    in case s/he wants to use multiple Ruby interpreters. The manual has
    also been updated to mention this tool.
  • Fixed streaming responses on Apache.
  • Worked around an OS X Unix domain socket bug. Fixes issue #854.
  • Out-of-Band Garbage Collection now works properly when the application
    has disabled garbage collection. Fixes issue #859.
  • Fixed support for /usr/bin/python on OS X. Fixes issue #855.
  • Fixed looping-without-sleeping in the ApplicationPool garbage collector
    if PassengerPoolIdleTime is set to 0. Fixes issue #858.
  • Fixed some process memory usage measurement bugs.
  • Fixed process memory usage measurement on NetBSD. Fixes issue #736.
  • Fixed a file descriptor leak in the Out-of-Band Work feature. Fixes issue #864.
  • The PassengerPreStart helper script now uses the default Ruby
    interpreter specified in the web server configuration, and no longer
    requires a ruby command to be in $PATH.
  • Updated preferred PCRE version to 8.32.
  • Worked around some RVM bugs and generally improved RVM support.
  • The ngx_http_stub_status_module is now enabled by default.
  • Performance optimizations.

Installing and testing 4.0.0 Release Candidate 6

Quick install/upgrade

Phusion Passenger Enterprise users can download the Enterprise version of 4.0 RC 6 from the Customer Area.

Open source users can install the open source version of 4.0 RC 6 with the following commands:

gem install passenger --pre

You can also download the tarball at Google Code.

In-depth instructions

In-depth installation and upgrade instructions can be found in the Installation section of the documentation. The documentation has been updated to cover 4.0 changes, including Enterprise features. You can view them online here:


We are excited about the final release. You can help us by testing RC 6 and reporting any bugs. Please submit bug reports to our bug tracker.

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