export APXS2=/opt/apache2/bin/apxs
Phusion Passenger is an Apache module, which makes deploying Ruby and Ruby on Rails applications on Apache a breeze. It follows the usual Ruby on Rails conventions, such as "Don't-Repeat-Yourself" and ease of setup, while at the same time providing enough flexibility.
This users guide will teach you:
How to install Phusion Passenger.
How to configure Phusion Passenger.
How to deploy a Ruby on Rails application.
How to deploy a Rack-based Ruby application.
How to solve common problems.
This guide assumes that the reader is somewhat familiar with Apache and with using the commandline.
Phusion Passenger works on any POSIX-compliant operating system. In other words: practically any operating system on earth, except Microsoft Windows.
Phusion Passenger has been tested on:
Ubuntu Linux 6.06 (x86)
Ubuntu Linux 7.10 (x86)
Debian Sarge (x86)
Debian Etch (x86)
Debian Lenny/Sid (x86)
CentOS 5 (x86)
Red Hat Enterprise Linux 5 (x86)
Gentoo, March 14 2008 (AMD64)
FreeBSD 6.1-RELEASE (x86)
MacOS X Tiger (x86)
MacOS X Leopard (x86)
Other operating systems have not been tested, but Phusion Passenger will probably work fine on them. Please report a bug or join our discussion list if it doesn't.
There are two ways to install Phusion Passenger:
By installing the Phusion Passenger gem, as instructed on the “Install” page on the Phusion Passenger website.
By downloading a native Linux package (e.g. Debian package) from the Phusion Passenger website.
By downloading the source tarball from the Phusion Passenger website (passenger-x.x.x.tar.gz).
In our opinion, installing the gem or the native package is easiest.
Phusion Passenger provides an easy-to-use installer for installing the Phusion Passenger Apache module (mod_passenger).
![]() |
You might have to run the installation commands in the following sections as root. If the installer fails because of permission errors, it will tell you. |
![]() |
You can skip this section if you've installed Phusion Passenger via a native Linux package, because no compilation is necessary. |
If your system has multiple Apache installations (this is likely the case on MacOS X), then you will need to tell the Phusion Passenger installer which one to use. If you only have one Apache installation (the case on most Linux systems), then you can skip this section because Phusion Passenger will automatically detect it.
Every Apache installation has its own apxs program. You will need to tell Phusion Passenger the location of this program, by specifying the APXS2 environment variable. Suppose that you want to use the Apache installation in /opt/apache2. Then, assuming that the corresponding apxs program is located /opt/apache2/bin/apxs, type:
export APXS2=/opt/apache2/bin/apxs
![]() |
On some systems, the apxs program might be called apxs2, and it might be located in the sbin folder instead of the bin folder. |
![]() |
You can skip this section if you've installed Phusion Passenger via a native Linux package, because no compilation is necessary. |
If your system has multiple Ruby installations (this is likely the case on MacOS X), then you will need to tell the Phusion Passenger installer which one to use. If you only have one Ruby installation (the case on most Linux systems), then you can skip this section because Phusion Passenger will automatically detect it.
To specify the Ruby installation, prepend your Ruby installation's bin directory to the PATH environment variable. For example, if you have the following Ruby installations:
/usr/bin/ruby
/opt/myruby/bin/ruby
and you want to use the latter, then type:
export PATH=/opt/myruby/bin:$PATH
Please install the gem and then run the Phusion Passenger installer, by typing the following commands:
gem install passenger-x.x.x.gem passenger-install-apache2-module
Please follow the instructions given by the installer.
Please install the native Linux package, e.g.:
gdebi passenger_x.x.x-i386.deb
Next, you'll need to configure Apache. Run the "installer", as it will tell you the correct configuration options for Apache:
passenger-install-apache2-module
![]() |
The installer doesn't actually install anything because it will automatically detect that Phusion Passenger has already been installed. The only thing the installer will do in this case, is showing the correct Apache configurations. |
Extract the tarball to whatever location you prefer. The Phusion Passenger files are to reside in that location permanently. For example, if you would like Phusion Passenger to reside in /opt/passenger-x.x.x:
cd /opt tar xzvf ~/YourDownloadsFolder/passenger-x.x.x.tar.gz
Next, run the included installer:
/opt/passenger-x.x.x/bin/passenger-install-apache2-module
Please follow the instructions given by the installer.
![]() |
Please do not remove the passenger-x.x.x folder after installation. Furthermore, the passenger-x.x.x folder must be accessible by Apache. |
Ben Ruebenstein has written an excellent tutorial on installing Phusion Passenger on OS X.
Ben Hughes has written an article on installing Phusion Passenger on Ubuntu.
Suppose you have a Ruby on Rails application in /webapps/mycook, and you own the domain www.mycook.com. You can either deploy your application to the virtual host's root (i.e. the application will be accessible from the root URL, http://www.mycook.com/), or in a sub URI (i.e. the application will be accessible from a sub URL, such as http://www.mycook.com/railsapplication).
![]() |
The default RAILS_ENV environment in which deployed Rails applications are run, is “production”. You can change this by changing the RailsEnv configuration option. |
Add a virtual host entry to your Apache configuration file. The virtual host's document root must point to your Ruby on Rails application's public folder. For example:
<VirtualHost *:80> ServerName www.mycook.com DocumentRoot /webapps/mycook/public </VirtualHost>
Then restart Apache. The application has now been deployed.
Suppose that you already have a virtual host:
<VirtualHost *:80> ServerName www.phusion.nl DocumentRoot /websites/phusion </VirtualHost>
And you want your Ruby on Rails application to be accessible from the URL http://www.phusion.nl/rails.
To do this, make a symlink from your Ruby on Rails application's public folder to a directory in the document root. For example:
ln -s /webapps/mycook/public /websites/phusion/rails
Next, add a RailsBaseURI option to the virtual host configuration:
<VirtualHost *:80> ServerName www.phusion.nl DocumentRoot /websites/phusion RailsBaseURI /rails # This line has been added. </VirtualHost>
Then restart Apache. The application has now been deployed.
![]() |
You can deploy multiple Rails applications under a virtual host, by specifying RailsBaseURI multiple times. For example: <VirtualHost *:80> .... RailsBaseURI /app1 RailsBaseURI /app2 RailsBaseURI /app3 </VirtualHost> |
Deploying a new version of a Ruby on Rails application is as simple as re-uploading the application files, and restarting the application.
There are two ways to restart the application:
By restarting Apache.
By creating or modifying the file tmp/restart.txt in the Rails application's root folder. Phusion Passenger will automatically restart the application.
For example, to restart our example MyCook application, we type this in the command line:
touch /webapps/mycook/tmp/restart.txt
Phusion Passenger is not related to Ruby on Rails migrations in any way. To run migrations on your deployment server, please login to your deployment server (e.g. with ssh) and type rake db:migrate RAILS_ENV=production in a shell console, just like one would normally run migrations.
See Capistrano recipe.
Phusion Passenger supports arbitrary Ruby web applications that follow the Rack interface.
Phusion Passenger assumes that Rack application directories have a certain layout. Suppose that you have a Rack application in /webapps/rackapp. Then that folder must contain at least two entries:
config.ru, a Rackup file for starting the Rack application. This file must contain the complete logic for initializing the application.
public/, a folder containing public static web assets, like images and stylesheets.
tmp/, used for restart.txt (our application restart mechanism). This will be explained in a following subsection.
So /webapps/rackapp must, at minimum, look like this:
/webapps/rackapp | +-- config.ru | +-- public/ | +-- tmp/
Suppose you own the domain www.rackapp.com. You can either deploy your application to the virtual host's root (i.e. the application will be accessible from the root URL, http://www.rackapp.com/), or in a sub URI (i.e. the application will be accessible from a sub URL, such as http://www.rackapp.com/rackapp).
![]() |
The default RACK_ENV environment in which deployed Rack applications are run, is “production”. You can change this by changing the RackEnv configuration option. |
First we create a Phusion Passenger-compliant Rack directory structure:
$ mkdir /webapps/rack_example $ mkdir /webapps/rack_example/public $ mkdir /webapps/rack_example/tmp
Next, we write a minimal "hello world" Rack application:
$ cd /webapps/rack_example $ some_awesome_editor config.ru ...type in some source code... $ cat config.ru app = proc do |env| return [200, { "Content-Type" => "text/html" }, "hello <b>world</b>"] end run app
Finally, we deploy it by adding the following configuration options to the Apache configuration file:
<VirtualHost *:80> ServerName www.rackexample.com DocumentRoot /webapps/rack_example/public </VirtualHost>
And we're done! After an Apache restart, the above Rack application will be available under the URL http://www.rackexample.com/.
Add a virtual host entry to your Apache configuration file. The virtual host's document root must point to your Rack application's public folder. For example:
<VirtualHost *:80> ServerName www.rackapp.com DocumentRoot /webapps/rackapp/public </VirtualHost>
Then restart Apache. The application has now been deployed.
Suppose that you already have a virtual host:
<VirtualHost *:80> ServerName www.phusion.nl DocumentRoot /websites/phusion </VirtualHost>
And you want your Rack application to be accessible from the URL http://www.phusion.nl/rack.
To do this, make a symlink from your Rack application's public folder to a directory in the document root. For example:
ln -s /webapps/rackapp/public /websites/phusion/rack
Next, add a RackBaseURI option to the virtual host configuration:
<VirtualHost *:80> ServerName www.phusion.nl DocumentRoot /websites/phusion RackBaseURI /rack # This line has been added. </VirtualHost>
Then restart Apache. The application has now been deployed.
![]() |
You can deploy multiple Rack applications under a virtual host, by specifying RackBaseURI multiple times. For example: <VirtualHost *:80> .... RackBaseURI /app1 RackBaseURI /app2 RackBaseURI /app3 </VirtualHost> |
Deploying a new version of a Rack application is as simple as re-uploading the application files, and restarting the application.
There are two ways to restart the application:
By restarting Apache.
By creating or modifying the file tmp/restart.txt in the Rack application's root folder. Phusion Passenger will automatically restart the application.
For example, to restart our example application, we type this in the command line:
touch /webapps/rackapp/tmp/restart.txt
This subsection shows example config.ru files for various web frameworks.
require 'rubygems' require 'rack' require 'camping' ##### Begin Camping application Camping.goes :Blog ...your application code here... ##### End Camping application run Rack::Adapter::Camping.new(Blog)
For Camping versions 2.0 and up, using run Blog as the final line will do.
require 'rubygems' require 'halcyon' $LOAD_PATH.unshift(Halcyon.root / 'lib') Halcyon::Runner.load_config Halcyon.root/'config'/'config.yml' run Halcyon::Runner.new
ENV["MACK_ENV"] = ENV["RACK_ENV"] load("Rakefile") require 'rubygems' require 'mack' run Mack::Utils::Server.build_app
require 'rubygems' require 'merb-core' Merb::Config.setup(:merb_root => ".", :environment => ENV['RACK_ENV']) Merb.environment = Merb::Config[:environment] Merb.root = Merb::Config[:merb_root] Merb::BootLoader.run run Merb::Rack::Application.new
require "start" Ramaze.trait[:essentials].delete Ramaze::Adapter Ramaze.start :force => true run Ramaze::Adapter::Base
require 'rubygems' require 'sinatra' root_dir = File.dirname(__FILE__) Sinatra::Application.default_options.merge!( :views => File.join(root_dir, 'views'), :app_file => File.join(root_dir, 'app.rb'), :run => false, :env => ENV['RACK_ENV'].to_sym ) run Sinatra.application
After installation, Phusion Passenger does not need any further configurations. Nevertheless, the system administrator may be interested in changing Phusion Passenger's behavior. Phusion Passenger's Apache module supports the following configuration options:
The location to the Phusion Passenger root directory. This configuration option is essential to Phusion Passenger. The correct value is given by the installer, and should usually not be changed manually.
This required option may only occur once, in the global server configuration.
This option allows one to specify how much information Phusion Passenger should write to the Apache error log file. A higher log level value means that more information will be logged.
Possible values are:
0: Show only errors and warnings.
1: Show the most important debugging information. This might be useful for system administrators who are trying to figure out the cause of a problem.
2: Show more debugging information. This is typically only useful for developers.
3: Show even more debugging information.
This option may only occur once, in the global server configuration. The default is 0.
This option allows one to specify the Ruby interpreter to use.
This option may only occur once, in the global server configuration. The default is ruby.
Turns the use of global queuing on or off.
This option may only occur once, in the global server configuration. The default is off.
This feature is sponsored by 37signals.
Recall that Phusion Passenger spawns multiple backend processes (e.g. multiple Ruby on Rails processes), each which processes HTTP requests serially. One of Phusion Passenger's jobs is to forward HTTP requests to a suitable backend process. A backend process may take an arbitrary amount of time to process a specific HTTP request. If the websites are (temporarily) under high load, and the backend processes cannot process the requests fast enough, then some requests may have to be queued.
If global queuing is turned off, then Phusion Passenger will use fair load balancing. This means that each backend process will have its own private queue. Phusion Passenger will forward an HTTP request to the backend process that has the least amount of requests in its queue.
If global queuing is turned on, then Phusion Passenger will use a global queue that's shared between all backend processes. If an HTTP request comes in, and all the backend processes are still busy, then Phusion Passenger will wait until at least one backend process is done, and will then forward the request to that process.
You should turn on global queuing if one of your web applications may have long-running requests.
For example suppose that:
global queuing is turned off.
we're currently in a state where all backend processes have 3 requests in their queue, except for a single backend process, which has 1 request in its queue.
The situation looks like this:
Backend process A: [* ] (1 request in queue) Backend process B: [*** ] (3 requests in queue) Backend process C: [*** ] (3 requests in queue) Backend process D: [*** ] (3 requests in queue)
Each process is currently serving short-running requests.
Phusion Passenger will forward the next request to backend process A. A will now have 2 items in its queue. We'll mark this new request with an X:
Backend process A: [*X ] (2 request in queue) Backend process B: [*** ] (3 requests in queue) Backend process C: [*** ] (3 requests in queue) Backend process D: [*** ] (3 requests in queue)
Assuming that B, C and D still aren't done with their current request, the next HTTP request - let's call this Y - will be forwarded to backend process A as well, because it has the least number of items in its queue:
Backend process A: [*XY ] (3 requests in queue) Backend process B: [*** ] (3 requests in queue) Backend process C: [*** ] (3 requests in queue) Backend process D: [*** ] (3 requests in queue)
But if request X happens to be a long-running request that needs 60 seconds to complete, then we'll have a problem. Y won't be processed for at least 60 seconds. It would have been a better idea if Y was forward to processes B, C or D instead, because they only have short-living requests in their queues.
This problem will be avoided entirely if you turn global queuing on. With global queuing, all backend processes will share the same queue. The first backend process that becomes available will take from the queue, and so this “queuing-behind-long-running-request” problem will never occur.
Turning global queuing off will yield a minor performance improvement (about 5%, depending on how fast/slow your web application is), which is why it's off by default.
Whether to enable user switching support.
This option may only occur once, in the global server configuration. The default value is on.
Passenger enables user switching support by default. This configuration option allows one to specify which user Rails/Rack applications must run as, if user switching fails or is disabled.
This option may only occur once, in the global server configuration. The default value is nobody.
The maximum number of Ruby on Rails or Rack application instances that may be simultaneously active. A larger number results in higher memory usage, but improved ability to handle concurrent HTTP clients.
The optimal value depends on your system's hardware and the server's average load. You should experiment with different values. But generally speaking, the value should be at least equal to the number of CPUs (or CPU cores) that you have. If your system has 2 GB of RAM, then we recommend a value of 30. If your system is a Virtual Private Server (VPS) and has about 256 MB RAM, and is also running other services such as MySQL, then we recommend a value of 2.
If you find that your server is unable to handle the load on your Rails/Rack websites (i.e. running out of memory) then you should lower this value. (Though if your sites are really that popular, then you should strongly consider upgrading your hardware or getting more servers.)
This option may only occur once, in the global server configuration. The default value is 6.
![]() |
We strongly recommend you to use Ruby Enterprise Edition. This allows you to reduce the memory usage of your Ruby on Rails applications by about 33%. And it's not hard to install. |
The maximum number of application instances that may be simultaneously active for a single application. This helps to make sure that a single application will not occupy all available slots in the application pool.
This value must be less than PassengerMaxPoolSize. A value of 0 means that there is no limit placed on the number of instances a single application may use, i.e. only the global limit of PassengerMaxPoolSize will be enforced.
This option may only occur once, in the global server configuration. The default value is 0.
The maximum number of seconds that an application instance may be idle. That is, if an application instance hasn't received any traffic after the given number of seconds, then it will be shutdown in order to conserve memory.
Decreasing this value means that applications will have to be spawned more often. Since spawning is a relatively slow operation, some visitors may notice a small delay when they visit your Rails/Rack website. However, it will also free up resources used by applications more quickly.
The optimal value depends on the average time that a visitor spends on a single Rails/Rack web page. We recommend a value of 2 * x, where x is the average number of seconds that a visitor spends on a single Rails/Rack web page. But your mileage may vary.
This option may only occur once, in the global server configuration. The default value is 300.
Whether Phusion Passenger should automatically detect whether a virtual host's document root is a Ruby on Rails application. The default is on.
This option may occur in the global server configuration or in a virtual host configuration block.
For example, consider the following configuration:
RailsAutoDetect off <VirtualHost *:80> ServerName www.mycook.com DocumentRoot /webapps/mycook/public </VirtualHost>
If one goes to http://www.mycook.com/, the visitor will see the contents of the /webapps/mycook/public folder, instead of the output of the Ruby on Rails application.
It is possible to explicitly specify that the host is a Ruby on Rails application by using the RailsBaseURI configuration option:
RailsAutoDetect off <VirtualHost *:80> ServerName www.mycook.com DocumentRoot /webapps/mycook/public RailsBaseURI / # This line has been added. </VirtualHost>
Used to specify that the given URI is a Rails application. See Deploying Rails to a sub URI for an example.
It is allowed to specify this option multiple times. Do this to deploy multiple Rails applications in different sub-URIs under the same virtual host.
This option may occur in the global server configuration or in a virtual host configuration block.
If enabled, Phusion Passenger will not override mod_rewrite rules. Please read Conflicting Apache modules for details.
This option may occur once, in the global server configuration or in a virtual host configuration block. The default value is off.
This option allows one to specify the default RAILS_ENV value.
This option may occur once, in the global server configuration or in a virtual host configuration block. The default value is production.
![]() |
"What spawn method should I use?"
This subsection attempts to describe spawn methods, but it's okay if you don't (want to) understand it, as it's mostly a technical detail. You can basically follow this rule of thumb: However, we do recommend you to try to understand it. The smart spawn method brings many benefits. |
Internally, Phusion Passenger spawns multiple Ruby on Rails processes in order to handle requests. But there are multiple ways with which processes can be spawned, each having its own set of pros and cons. Supported spawn methods are:
When this spawn method is used, Phusion Passenger will attempt to cache Ruby on Rails framework code and application code for a limited period of time.
Pros: This can significantly decrease spawn time (by as much as 90%). And, when Ruby Enterprise Edition is used, memory usage can be reduced by 33% on average.
Cons: Some Ruby on Rails applications and libraries are not compatible with smart spawning. If that's the case for your application, then you should use conservative as spawning method.
This spawning method is similar to the one used in Mongrel Cluster. It does not perform any code caching at all.
Pros: Conservative spawning is guaranteed to be compatible with all Rails applications and libraries.
Cons: Much slower than smart spawning. Every spawn action will be equally slow, though no slower than the startup time of a single server in Mongrel Cluster. Conservative spawning will also render Ruby Enterprise Edition's memory reduction technology useless.
This option may occur once, in the global server configuration or in a virtual host configuration block. The default value is smart.
Whether Phusion Passenger should automatically detect whether a virtual host's document root is a Rack application. The default is on.
This option may occur in the global server configuration or in a virtual host configuration block.
For example, consider the following configuration:
RackAutoDetect off <VirtualHost *:80> ServerName www.rackapp.com DocumentRoot /webapps/my_rack_app/public </VirtualHost>
If one goes to http://www.rackapp.com/, the visitor will see the contents of the /webapps/my_rack_app/public folder, instead of the output of the Rack application.
It is possible to explicitly specify that the host is a Rack application by using the RackBaseURI configuration option:
RackAutoDetect off <VirtualHost *:80> ServerName www.rackapp.com DocumentRoot /webapps/my_rack_app/public RackBaseURI / # This line was added </VirtualHost>
Used to specify that the given URI is a Rack application. See Deploying Rack to a sub URI for an example.
It is allowed to specify this option multiple times. Do this to deploy multiple Rack applications in different sub-URIs under the same virtual host.
This option may occur in the global server configuration or in a virtual host configuration block.
The given value will be accessible in Rack applications in the RACK_ENV environment variable. This allows one to define the environment in which Rack applications are run, very similar to RAILS_ENV.
This option may occur once, in the global server configuration or in a virtual host configuration block. The default value is production.
The following options have been deprecated, but are still supported for backwards compatibility reasons.
Deprecated in favor of PassengerRuby.
Deprecated in favor of PassengerUserSwitching.
Deprecated in favor of PassengerDefaultUser.
Your MAMP installation seems to be broken. In particular, config_vars.mk is missing. Please read this forum topic to learn how to fix this problem.
See also this bug report.
Phusion Passenger makes use of a native extension, so the Ruby development headers must be installed. On most Linux systems, Ruby and the Ruby development headers are contained in separate packages, so having Ruby installed does not automatically imply having the development headers installed.
Here's how you can install the development headers:
Please type:
sudo apt-get install ruby1.8-dev
Please type:
su -c 'yum install ruby-devel'
Please install Ruby from ports or with pkg_add. If that fails, please install Ruby from source.
Please install Ruby from source.
Please consult your operating system's native package database. There should be a package containing the Ruby development headers. If that fails, please install Ruby from source.
![]() |
If you've installed a new Ruby version (i.e. your system now contains multiple Ruby installations), then you will need to tell Phusion Passenger which Ruby installation you want to use. Please read Specifying the correct Ruby installation. |
Please type:
sudo apt-get install apache2-prefork-dev
Please type:
sudo apt-get install apache2-dev
Please type:
su -c 'yum install httpd-devel'
Please install Apache from ports or with pkg_add. If that fails, please install Apache from source.
Please install Apache from source.
Please consult your operating system's native package database. There should be a package containing the Apache development headers. If that fails, please install Apache from source.
Please type:
sudo apt-get install libapr1-dev
Please type:
sudo apt-get install libapr1-dev
Please type:
su -c 'yum install apr-devel'
Please consult your distribution's package database. There should be a package which provides APR development headers.
The APR development are bundled with Apache. If the APR headers aren't, then it probably means that they have been removed after Apache's been installed. Please reinstall Apache to get back the APR headers.
Please Specifying the correct Apache installation, and re-run the Phusion Passenger installer.
Please Specifying the correct Ruby installation, and re-run the Phusion Passenger installer.
![]() |
The golden tip: read your Apache error logs!
mod_passenger will write all errors to the Apache error log. So if you're experiencing post-installation problems, please look inside the Apache error logs. It will tell you what exactly went wrong. |
Please try setting RailsSpawnMethod to conservative.
This problem is most likely to occur on MacOS X. Most OS X users have multiple Apache installations on their system.
To solve this problem, please specify the correct Apache installation, and reinstall Phusion Passenger.
See next subsection.
Static assets are accelerated, i.e. they are served directly by Apache and do not go through the Rails stack. There are two reasons why Apache doesn't serve static assets correctly:
Your Apache configuration is too strict, and does not allow HTTP clients to access static assets. This can be achieved with an Allow from all directive in the correct place. For example:
<Directory "/webapps/mycook/public"> Options FollowSymLinks AllowOverride None Order allow,deny Allow from all </Directory>
See also this discussion.
The Apache process doesn't have permission to access your Rails application's folder. Please make sure that the Rails application's folder, as well as all of its parent folders, have the correct permissions and/or ownerships.
If you are sure that the PassengerRoot configuration option is set correctly, then this problem is most likely caused by the fact that you're running Apache with SELinux. On Fedora, CentOS and RedHat Enterprise Linux, Apache is locked down by SELinux policies.
To solve this problem, you must set some permissions on the Phusion Passenger files and folders, so that Apache can access them.
If you've installed Phusion Passenger via a gem, then run this command to determine Phusion Passenger's root folder:
passenger-config --root
Next, run the following command:
chcon -R -h -t httpd_sys_content_t /path-to-passenger-root
where /path-to-passenger-root should be replaced with whatever passenger-config —root printed.
If you've installed Phusion Passenger via the source tarball, then run the following command:
chcon -R -h -t httpd_sys_content_t /path/to/passenger/folder
Once the permissions are fixed, restart Apache.
Please check whether your Rails application's folder has the correct permissions. By default, Rails applications are started as the owner of the file config/environment.rb, except if the file is owned by root. If the file is owned by root, then the Rails application will be started as nobody (or as the user specify by RailsDefaultUser, if that's specified).
Please read User switching (security) for details.
There are a couple things that you should be aware of:
By default, Phusion Passenger runs Rails applications in production mode, so please be sure to check production.log instead of development.log. See RailsEnv for configuration.
By default, Phusion Passenger runs Rails applications as the owner of environment.rb. So the log file can only be written to if that user has write permission to the log file. Please chmod or chown your log file accordingly.
See User switching (security) for details.
If you're using a RedHat-derived Linux distribution (such as Fedora or CentOS) then it is possible that SELinux is interfering. RedHat's SELinux policy only allows Apache to read/write directories that have the httpd_sys_content_t security context. Please run the following command to give your Rails application folder that context:
chcon -R -h -t httpd_sys_content_t /path/to/your/rails/app
Phusion Passenger conflicts with mod_rewrite and mod_alias. Those modules may be installed and loaded together with mod_passenger, and they will work fine outside virtual hosts that contain a Rails application, but we recommend you not to use their features inside virtual hosts that contain a Rails application.
By default, Phusion Passenger will override mod_rewrite rules on Rails hosts. This is because the default .htaccess, as provided by Ruby on Rails, redirects all requests to `dispatch.cgi' using mod_rewrite. This is a CGI application which loads the entire Ruby on Rails framework for every request, and thus is very slow. If we do not override mod_rewrite, then Ruby on Rails apps will be slow on Phusion Passenger by default — but we want a good out-of-the-box experience.
Furthermore, the primary reason why people use mod_rewrite with Rails applications, is to accelerate page caching. Phusion Passenger supports page caching out-of-the-box, without mod_rewrite.
It is not fully understood how mod_alias conflicts with Phusion Passenger, but we recommend you not to use it on Rails virtual hosts. mod_alias rules can result in surprising problems.
If you really want to use mod_rewrite on Rails virtual hosts, then please set the RailsAllowModRewrite configuration option. But please note that you will have to delete Rails applications' default .htaccess file, or add rewrite rules to negate its effects.
mod_userdir is not compatible with Phusion Passenger at the moment.
VirtualDocumentRoot is not compatible with Phusion Passenger at the moment.
Phusion Passenger provides a set of tools, which are useful for system analysis, maintenance and troubleshooting.
Process inspection tools such as ps and top are useful, but they rarely show the correct memory usage. The real memory usage is usually lower than what ps and top report.
There are many technical reasons why this is so, but an explanation is beyond the scope of this Users Guide. We kindly refer the interested reader to operating systems literature about virtual memory and copy-on-write.
The tool passenger-memory-stats allows one to easily analyze Phusion Passenger's and Apache's real memory usage. For example:
[bash@localhost root]# passenger-memory-stats ------------- Apache processes --------------. PID PPID Threads VMSize Private Name ---------------------------------------------. 5947 1 9 90.6 MB 0.5 MB /usr/sbin/apache2 -k start 5948 5947 1 18.9 MB 0.7 MB /usr/sbin/fcgi-pm -k start 6029 5947 1 42.7 MB 0.5 MB /usr/sbin/apache2 -k start 6030 5947 1 42.7 MB 0.5 MB /usr/sbin/apache2 -k start 6031 5947 1 42.5 MB 0.3 MB /usr/sbin/apache2 -k start 6033 5947 1 42.5 MB 0.4 MB /usr/sbin/apache2 -k start 6034 5947 1 50.5 MB 0.4 MB /usr/sbin/apache2 -k start 23482 5947 1 82.6 MB 0.4 MB /usr/sbin/apache2 -k start ### Processes: 8 ### Total private dirty RSS: 3.50 MB --------- Passenger processes ---------. PID Threads VMSize Private Name ---------------------------------------. 6026 1 10.9 MB 4.7 MB Passenger spawn server 23481 1 26.7 MB 3.0 MB Passenger FrameworkSpawner: 2.0.2 23791 1 26.8 MB 2.9 MB Passenger ApplicationSpawner: /var/www/projects/app1-foobar 23793 1 26.9 MB 17.1 MB Rails: /var/www/projects/app1-foobar ### Processes: 4 ### Total private dirty RSS: 27.76 M
The Private or private dirty RSS field shows the real memory usage of processes. Here, we see that all the Apache worker processes only take less than 1 MB memory each. This is a lot less than the 50 MB-ish memory usage as shown in the VMSize column (which is what a lot of people think is the real memory usage, but is actually not).
![]() |
This tool only works on Linux. Unfortunately other operating systems don't provide facilities for determining processes' private dirty RSS. |
One can inspect Phusion Passenger's internal status with the tool passenger-status. This tool must typically be run as root. For example:
[bash@localhost root]# passenger-status ----------- General information ----------- max = 6 count = 1 active = 0 inactive = 1 ----------- Applications ----------- /var/www/projects/app1-foobar: PID: 9617 Sessions: 0
The general information section shows the following information:
max | The maximum number of application instances that Phusion Passenger will spawn. This equals the value given for PassengerMaxPoolSize. |
count | The number of application instances that are currently alive. This value is always less than or equal to max. |
active | The number of application instances that are currently processing requests. This value is always less than or equal to count. |
inactive | The number of application instances that are currently not processing requests, i.e. are idle. Idle application instances will be shutdown after a while, as can be specified with PassengerPoolIdleTime. The value of inactive equals count - active. |
The applications section shows each application instance, which directory it belongs to. The sessions field shows how many HTTP client are currently being processed by that application instance.
Since Phusion Passenger uses fair load balancing by default, the number of sessions for the application instances should be fairly close to each other. For example, this is fairly normal:
PID: 4281 Sessions: 2 PID: 4268 Sessions: 0 PID: 4265 Sessions: 1 PID: 4275 Sessions: 1
But if you see a "spike", i.e. an application instance has an unusually high number of sessions compared to the others, then there might be a problem:
PID: 4281 Sessions: 2 PID: 17468 Sessions: 8 <---- "spike" PID: 4265 Sessions: 1 PID: 4275 Sessions: 1
Possible reasons why spikes can occur:
Your application is busy processing a request that takes a very long time. If this is the case, then you might want to turn global queuing on.
Your application is frozen, i.e. has stopped responding. See Debugging frozen applications for tips.
If one of your application instances is frozen (stopped responding), then you can figure out where it is frozen by killing it with SIGABRT. This will cause the application to raise an exception, with a backtrace.
The exception (with full backtrace information) is normally logged into the Apache error log. But if your application or if its web framework has its own exception logging routines, then exceptions might be logged into the application's log files instead. This is the case with Ruby on Rails. So if you kill a Ruby on Rails application with SIGABRT, please check the application's production.log first (assuming that you're running it in a production environment). If you don't see a backtrace there, check the Apache error log.
![]() |
It is safe to kill application instances, even in live environments. Phusion Passenger will restart killed application instances, as if nothing bad happened. |
There is a problem that plagues most PHP web host, namely the fact that all PHP applications are run in the same user context as the web server. So for example, Joe's PHP application will be able to read Jane's PHP application's passwords. This is obviously undesirable on many servers.
Phusion Passenger solves this problem by implementing user switching. A Rails application is started as the owner of the file config/environment.rb, and a Rack application is started as the owner of the file config.ru. So if /home/webapps/foo/config/environment.rb is owned by joe, then Phusion Passenger will launch the corresponding Rails application as joe as well.
This behavior is the default, and you don't need to configure anything. But there are things that you should keep in mind:
The owner of environment.rb must have read access to the Rails application's folder, and read/write access to the Rails application's logs folder. Likewise, the owner of config.ru must have read access to the Rack application's folder.
This feature is only available if Apache is started by root. This is the case on most Apache installations.
Under no circumstances will applications be run as root. If environment.rb/config.ru is owned as root or by an unknown user, then the Rails/Rack application will run as the user specified by PassengerDefaultUser.
User switching can be disabled with the PassengerUserSwitching option.
Is it possible to reduce memory consumption of your Rails applications by 33% on average, by using Ruby Enterprise Edition. Please visit the website for details.
Note that this feature does not apply to Rack applications.
Phusion Passenger can be combined with Capistrano. The following Capistrano recipe demonstrates Phusion Passenger support. It assumes that you're using Git as version control system.
set :application, "myapp" set :domain, "example.com" set :repository, "ssh://#{domain}/path-to-your-git-repo/#{application}.git" set :use_sudo, false set :deploy_to, "/path-to-your-web-app-directory/#{application}" set :scm, "git" role :app, domain role :web, domain role :db, domain, :primary => true namespace :deploy do desc "Restart Application" task :restart, :roles => :app do run "touch #{current_path}/tmp/restart.txt" end end
![]() |
You may notice that for each deploy, a new spawner server is created (it'll show up in passenger-memory-stats). Indeed, Capistrano will deploy to a path ending with /current (ie : /var/www/yourapp/current), so that you don't have to care about revisions in your virtual host configuration. This /current directory is a symlink to the current revision deployed (/path_to_app/releases/date_of_the_release). Therefore, when deploying a new version, the symlink will change, and Phusion Passenger will think it's a new application, thereby creating a new spawner server: 1001 30291 [...] Passenger ApplicationSpawner: /var/www/my_app/releases/20080509104413 1001 31371 [...] Passenger ApplicationSpawner: /var/www/my_app/releases/20080509104632 Don't worry about this. The (old) spawner server will terminate itself after its default timeout (10 minutes), so you will not run out of memory. If you really want to release the spawner server's memory immediately, then you can add a command to your Capistrano script to terminate the Passenger spawn server after each deploy. That command is as follows: kill $( passenger-memory-stats | grep 'Passenger spawn server' | awk '{ print $1 }' ) Killing the spawn server is completely safe, because Phusion Passenger will restart the spawn server if it has been terminated. |
It is possible to relocate the Phusion Passenger files to a different directory. It involves two steps:
Moving the directory.
Updating the “PassengerRoot” configuration option in Apache.
For example, if Phusion Passenger is located in /opt/passenger/, and you'd like to move it to /usr/local/passenger/, then do this:
Run the following command:
mv /opt/passenger /usr/local/passenger
Edit your Apache configuration file, and set:
PassengerRoot /usr/local/passenger
Each Ruby on Rails applications that are going to be deployed may require a specific Ruby on Rails version. You can install a specific version with this command:
gem install rails -v X.X.X
where X.X.X is the version number of Ruby on Rails.
All of these versions will exist in parallel, and will not conflict with each other. Phusion Passenger will automatically make use of the correct version.
Phusion Passenger does not provide X-Sendfile support by itself. Please install mod_xsendfile for X-Sendfile support.
Phusion Passenger does not provide upload progress support by itself. Please try drogus's Apache upload progress module instead.
The text of this document is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported License.
Phusion Passenger is brought to you by Phusion.
Phusion Passenger is a trademark of Hongli Lai & Ninh Bui.