Phusion white papers Phusion overview

Phusion Blog

Phusion Passenger 4.0.19 released

By Hongli Lai on September 24th, 2013

Phusion Passenger is a fast and robust web server and application server for Ruby, Python and Node.js. It works by integrating into Apache and Nginx and turning them into a fully-featured application server. It has high-profile users such as New York Times, AirBnB, Juniper, Motorola, etc, and comes with many features that make your life easier and your application perform better.

Phusion Passenger is under constant maintenance and development. Version 4.0.19 is a bugfix release.

Phusion Passenger also has an Enterprise version which comes with a wide array of additional features. By buying Phusion Passenger Enterprise you will directly sponsor the development of the open source version.

Recent changes

Version 4.0.18 was a test release for testing Debian packaging fixes and Heroku fixes, so its announcement has been skipped. The changes in 4.0.18 and 4.0.19 together are as follows:

  • Fixed a problem with response buffering. Application processes are now properly marked available for request processing immediately after they’re done sending the response, instead of after having sent the entire response to the client.
  • The "processed" counter in `passenger-status` is now bumped after the process has handled a request, not at the beginning.
  • The Enterprise variant of Phusion Passenger Standalone now supports customizing the concurrency model and thread count from the command line.
  • On Nginx, the Enterprise license is now only checked if Phusion Passenger is enabled in Nginx. This allows you to deploy Nginx binaries, that have Phusion Passenger Enterprise compiled in, to servers that are not actually running Phusion Passenger Enterprise.
  • Fixed a performance bug in the [Union Station]( support code. In certain cases where a lot of data must be sent to Union Station, the code is now over 100 times faster.
  • `passenger-status –show=union_station` now displays all clients that are connected to the LoggingAgent.
  • Added a workaround for Heroku so that exited processes are properly detected as such.
  • When using Phusion Passenger Standalone with Foreman, pressing Ctrl-C in Foreman no longer results in runaway Nginx processes.
  • Fixed backtraces in the Apache module.
  • [Enterprise] Fixed an off-by-one bug in the `passenger_max_processes` setting.

Installing 4.0.19

Quick install/upgrade

Phusion Passenger Enterprise users can download the Enterprise version of 4.0.19 from the Customer Area.

Open source users can install the open source version of 4.0.19 with the following commands. Note that these instructions are very basic and may not cover steps that may be relevant to your specific system, such as setting up the right file permission. Please refer to the in-depth instructions if you have trouble installing.

gem install passenger

You can also download the tarball at the Release Archive page. We strongly encourage you to cryptographically verify files after downloading them.

In-depth instructions

In-depth installation and upgrade instructions can be found in the Installation section of the documentation. The documentation covers.

  • Detailed tarball installation instructions.
  • Detailed upgrade instructions.
  • Installation troubleshooting.
  • Installation through APT and YUM.
  • Installation through OS X Homebrew.

You can view the documentation online here:


Phusion Passenger’s core is open source. Please fork or watch us on Github. 🙂

If you would like to stay up to date with Phusion news, please fill in your name and email address below and sign up for our newsletter. We won’t spam you, we promise.