Users guide Apache.txt

Phusion Passenger users guide, Apache version
=============================================

image:images/phusion_banner.png[link="http://www.phusion.nl/"]

Phusion Passenger is an application server which can directly integrate into Apache. It is designed to be easy to use, fast, stable and reliable and is used by link:http://trends.builtwith.com/Web-Server/Phusion-Passenger[hundreds of thousands of websites] all over the world.

Phusion Passenger is a so-called polyglot application server because it supports applications written in multiple programming languages. At this time, Ruby and Python are supported.

This users guide will teach you:

- How to install Phusion Passenger.
- How to configure Phusion Passenger.
- How to deploy Ruby and Python applications.
- How to solve common problems.

This guide assumes that the reader is somewhat familiar with Apache and with
using the command line.


== Support information

include::users_guide_snippets/support_information.txt[]

== Installation

include::users_guide_snippets/installation.txt[]


== Deploying a Ruby on Rails 1.x or 2.x (but NOT Rails >= 3.x) application ==

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').

NOTE: The default `RAILS_ENV` environment in which deployed Rails applications
are run, is ``production''. You can change this by changing the
<<rails_env,'RailsEnv'>> configuration option.

=== Deploying to a virtual host's root ===

Add a virtual host entry to your Apache configuration file. Make sure that the
following conditions are met:

- The virtual host's document root must point to your Ruby on Rails application's
  'public' folder.
- The Apache per-directory permissions must allow access to this folder.
- MultiViews must be disabled for this folder.

For example:
-------------------------------------------
<VirtualHost *:80>
    ServerName www.mycook.com
    DocumentRoot /webapps/mycook/public
    <Directory /webapps/mycook/public>
        Allow from all
        Options -MultiViews
    </Directory>
</VirtualHost>
-------------------------------------------

You may also need to tweak your file/folder permissions. Make sure that the
following folders are readable and executable by Apache:

 * this 'public' folder.
 * the application's 'config' folder.
 * all parent folders. That is, /webapps/mycook and /webapps must also be readable and executable by Apache.

Then restart Apache. The application has now been deployed.

[[deploying_rails_to_sub_uri]]
=== Deploying to a sub URI ===

Suppose that you already have a virtual host:

-------------------------------------------
<VirtualHost *:80>
    ServerName www.phusion.nl
    DocumentRoot /websites/phusion
    <Directory /websites/phusion>
        Allow from all
    </Directory>
</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 in the virtual host's document root, and have it
point to your Ruby on Rails application's 'public' folder. For example:
-------------------------------------------
ln -s /webapps/mycook/public /websites/phusion/rails
-------------------------------------------

Next, add a <<RailsBaseURI,RailsBaseURI>> option to the virtual host configuration,
and also make sure that:

- The Apache per-directory permissions allow access to this folder.
- MultiViews is disabled for this folder.

For example:
-------------------------------------------
<VirtualHost *:80>
    ServerName www.phusion.nl
    DocumentRoot /websites/phusion
    <Directory /websites/phusion>
        Allow from all
    </Directory>
    
    RailsBaseURI /rails                   # <-- These lines have
    <Directory /websites/phusion/rails>   # <-- been added.
        Options -MultiViews               # <--
    </Directory>                          # <--
</VirtualHost>
-------------------------------------------
Then restart Apache. The application has now been deployed.

NOTE: If you're deploying to a sub-URI then please make sure that your view
templates correctly handles references to sub-URI static assets! Otherwise
you may find broken links to images, CSS files, JavaScripts, etc. Please read
<<sub_uri_deployment_uri_fix,How to fix broken images/CSS/JavaScript URIs in sub-URI deployments>>
for more information.

[TIP]
======================================
You can deploy multiple Rails applications under a virtual host, by specifying
<<RailsBaseURI,RailsBaseURI>> multiple times. For example:
---------------------------------
<VirtualHost *:80>
    ....
    RailsBaseURI /app1
    RailsBaseURI /app2
    RailsBaseURI /app3
</VirtualHost>
---------------------------------
======================================

=== Redeploying (restarting the Ruby on Rails application) ===

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:

1. By restarting Apache.
2. By creating or modifying the file 'tmp/restart.txt' in the Rails
   application's <<application_root,root folder>>. Phusion Passenger will
   automatically restart the application during the next request.

For example, to restart our example MyCook application, we type this in the
command line:
-------------------------------------------
touch /webapps/mycook/tmp/restart.txt
-------------------------------------------

Please note that, unlike earlier versions of Phusion Passenger, 'restart.txt'
is not automatically deleted. Phusion Passenger checks whether the timestamp
of this file has changed in order to determine whether the application should
be restarted.

=== Migrations ===

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.

=== Capistrano integration ===

See <<capistrano,Capistrano recipe>>.


== Deploying a Rack-based Ruby application (including Rails >= 3) ==

Phusion Passenger supports arbitrary Ruby web applications that follow the
link:http://rack.rubyforge.org/[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 three 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').

NOTE: The default `RACK_ENV` environment in which deployed Rack applications
are run, is ``production''. You can change this by changing the
<<rack_env,'RackEnv'>> configuration option.

=== Tutorial/example: writing and deploying a Hello World Rack application ===

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|
    [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
    <Directory /webapps/rack_example/public>
        Allow from all
        Options -MultiViews
    </Directory>
</VirtualHost>
-------------------------------------------

And we're done! After an Apache restart, the above Rack application will be available
under the URL 'http://www.rackexample.com/'.

=== Deploying to a virtual host's root ===

Add a virtual host entry to your Apache configuration file. Make sure that the
following conditions are met:

- The virtual host's document root must point to your Rack application's
  'public' folder.
- The Apache per-directory permissions must allow access to this folder.
- MultiViews must be disabled for this folder.

For example:
-------------------------------------------
<VirtualHost *:80>
    ServerName www.rackapp.com
    DocumentRoot /webapps/rackapp/public
    <Directory /webapps/rackapp/public>
        Allow from all
        Options -MultiViews
    </Directory>
</VirtualHost>
-------------------------------------------

You may also need to tweak your file/folder permissions. Make sure that the
following folders are readable and executable by Apache:

 * this 'public' folder.
 * the application's 'config' folder.
 * all parent folders. That is, /webapps/rackapp and /webapps must also be readable and executable by Apache.

Then restart Apache. The application has now been deployed.

[[deploying_rack_to_sub_uri]]
=== Deploying to a sub URI ===

Suppose that you already have a virtual host:

-------------------------------------------
<VirtualHost *:80>
    ServerName www.phusion.nl
    DocumentRoot /websites/phusion
    <Directory /websites/phusion>
        Allow from all
    </Directory>
</VirtualHost>
-------------------------------------------

And you want your Rack application to be accessible from the URL
'http://www.phusion.nl/rack'.

To do this, make a symlink in the virtual host's document root, and have it
point to your Rack application's 'public' folder. For example:
-------------------------------------------
ln -s /webapps/rackapp/public /websites/phusion/rack
-------------------------------------------

Next, add a <<RackBaseURI,RackBaseURI>> option to the virtual host configuration,
and also make sure that:

- The Apache per-directory permissions allow access to this folder.
- MultiViews is disabled for this folder.

For example:
-------------------------------------------
<VirtualHost *:80>
    ServerName www.phusion.nl
    DocumentRoot /websites/phusion
    <Directory /websites/phusion>
        Allow from all
    </Directory>

    RackBaseURI /rack                     # <-- These lines have
    <Directory /websites/phusion/rack>    # <-- been added.
        Options -MultiViews               # <--
    </Directory>                          # <--
</VirtualHost>
-------------------------------------------
Then restart Apache. The application has now been deployed.

[TIP]
======================================
You can deploy multiple Rack applications under a virtual host, by specifying
<<RackBaseURI,RackBaseURI>> multiple times. For example:
---------------------------------
<VirtualHost *:80>
    ....
    RackBaseURI /app1
    RackBaseURI /app2
    RackBaseURI /app3
</VirtualHost>
---------------------------------
======================================

=== Redeploying (restarting the Rack application) ===

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:

1. By restarting Apache.
2. By creating or modifying the file 'tmp/restart.txt' in the Rack
   application's <<application_root,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
-------------------------------------------

=== Rackup specifications for various web frameworks ===
include::users_guide_snippets/rackup_specifications.txt[]


== Deploying a WSGI (Python) application

Phusion Passenger supports all WSGI-compliant Python web applications. Suppose that you have a WSGI application in '/webapps/wsgiapp'. Then that folder must contain at least three entries:

- 'passenger_wsgi.py', which Phusion Passenger will use as the main entry point for your application. This file must export a WSGI object called `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/wsgiapp' must, at minimum, look like this:
----------------------
/webapps/wsgiapp
  |
  +-- config.ru
  |
  +-- public/
  |
  +-- tmp/
----------------------

=== Tutorial/example: writing and deploying a Hello World WSGI application ===

First we create a Phusion Passenger-compliant WSGI directory structure:

-------------------------------------------
$ mkdir /webapps/wsgi_example
$ mkdir /webapps/wsgi_example/public
$ mkdir /webapps/wsgi_example/tmp
-------------------------------------------

Next, we write a minimal "hello world" WSGI application:

-------------------------------------------
$ cd /webapps/wsgi_example
$ some_awesome_editor passenger_wsgi.py
...type in some source code...
$ cat passenger_wsgi.py
def application(environ, start_response):
  start_response('200 OK', [('Content-Type', 'text/plain')])
  return [b"hello world!\n"]
-------------------------------------------

Finally, we deploy it by adding the following configuration options to
the Apache configuration file:

-------------------------------------------
<VirtualHost *:80>
    ServerName www.wsgiexample.com
    DocumentRoot /webapps/wsgi_example/public
    <Directory /webapps/wsgi_example/public>
        Allow from all
        Options -MultiViews
    </Directory>
</VirtualHost>
-------------------------------------------

And we're done! After an Apache restart, the above WSGI application will be available
under the URL 'http://www.wsgiexample.com/'.

=== Deploying to a virtual host's root ===

Add a virtual host entry to your Apache configuration file. Make sure that the
following conditions are met:

- The virtual host's document root must point to your WSGI application's
  'public' folder.
- The WSGI per-directory permissions must allow access to this folder.
- MultiViews must be disabled for this folder.

For example:
-------------------------------------------
<VirtualHost *:80>
    ServerName www.wsgiapp.com
    DocumentRoot /webapps/wsgiapp/public
    <Directory /webapps/wsgiapp/public>
        Allow from all
        Options -MultiViews
    </Directory>
</VirtualHost>
-------------------------------------------

You may also need to tweak your file/folder permissions. Make sure that the
following folders are readable and executable by Apache:

 * this 'public' folder.
 * the application's 'config' folder.
 * all parent folders. That is, /webapps/wsgiapp and /webapps must also be readable and executable by Apache.

Then restart Apache. The application has now been deployed.

=== Redeploying (restarting the WSGI application) ===

Deploying a new version of a WSGI application is as simple as
re-uploading the application files, and restarting the application.

There are two ways to restart the application:

1. By restarting Apache.
2. By creating or modifying the file 'tmp/restart.txt' in the WSGI
   application's <<application_root,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/wsgiapp/tmp/restart.txt
-------------------------------------------


== Configuring Phusion Passenger ==

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:

=== PassengerRoot <directory> ===
The location to the Phusion Passenger root directory. This configuration option
is essential to Phusion Passenger, and allows Phusion Passenger to locate its own
data files. The correct value is given by the installer.

If you've moved Phusion Passenger to a different directory then you need to update
this option as well. Please read
<<moving_phusion_passenger,Moving Phusion Passenger to a different directory>> for more information.

This required option may only occur once, in the global server configuration.

[[PassengerDefaultRuby]]
=== PassengerDefaultRuby <filename> ===
:version: 4.0.0
include::users_guide_snippets/since_version.txt[]

This option specifies the default Ruby interpreter to use for web apps as well as for all sorts of internal Phusion Passenger helper scripts, e.g. the one used by <<PassengerPreStart,PassengerPreStart>>. Please see <<PassengerRuby,PassengerRuby>> for more information, as well as how it relates to <<PassengerRuby,PassengerRuby>>.

This option may occur in the global server configuration. The default value is 'ruby', meaning that the Ruby interpreter will be looked up according to the `PATH` environment variable.

[[PassengerRuby]]
=== PassengerRuby <filename> ===
The `PassengerDefaultRuby` and `PassengerRuby` directives specify the Ruby interpreter to use. Similarly, the `PassengerPython` directive is for specifying the Python interpreter.

The relationship between `PassengerDefaultRuby` and `PassengerRuby` is as follows:

 * `PassengerDefaultRuby` may only occur in the global server configuration.
 * `PassengerRuby` may occur everywhere: in the global server configuration, in `<VirtualHost>`, in `<Directory>`, in `<Location>`, and in '.htaccess' if `AllowOverride Options` is on.
 * You don't *have* to specify `PassengerRuby`. In this case `PassengerDefaultRuby` is used as the Ruby interpreter. But if you do specify `PassengerRuby` then it will override `PassengerDefaultRuby` in that context. This allows you to use `PassengerRuby` to specify a different Ruby interpreter on a per-application basis.

Phusion Passenger not only uses Ruby to run web apps, but also for running certain helper tools that are written in Ruby, e.g. the internal helper script used by <<PassengerPreStart,PassengerPreStart>>. These tools are always run using `PassengerDefaultRuby`, never by `PassengerRuby`. `PassengerRuby` is only used for running web apps. You can learn more about the internal helper scripts in <<relationship_with_ruby,Phusion Passenger and its relationship with Ruby>>.

It is okay if `PassengerDefaultRuby` refers to a different Ruby interpreter than the one you originally installed Phusion Passenger with. This too is explained in <<relationship_with_ruby,Phusion Passenger and its relationship with Ruby>>.

The reason why `PassengerDefaultRuby` exists at all is because limitations in the Apache API prevents us from implementing the same behavior using only the `PassengerRuby` directive.

There is no `PassengerDefaultPython` because there are no Phusion Passenger tools written in Python. As such, having `PassengerPython` is enough.

The following example illustrates how it works and how you can use these options to specify different Ruby/Python interpreters for different web apps.

------------------------------
# Use Ruby 1.8.7 by default.
PassengerDefaultRuby /usr/bin/ruby1.8
# Use Python 2.6 by default.
PassengerPython /usr/bin/python2.6

<VirtualHost *:80>
    # This Rails web app will use Ruby 1.8.7
    ServerName www.foo.com
    DocumentRoot /webapps/foo/public
</VirtualHost>

<VirtualHost *:80>
    # This Rails web app will use Ruby 1.9.3, as installed by RVM
    PassengerRuby /usr/local/rvm/wrappers/ruby-1.9.3/ruby
    ServerName www.bar.com
    DocumentRoot /webapps/bar/public

    # If you have a web app deployed in a sub-URI, customize
    # PassengerRuby/PassengerPython inside a <Location> block.
    # The web app under www.bar.com/blog will use JRuby 1.7.1
    RackBaseURI /blog
    <Location /blog>
        PassengerRuby /usr/local/rvm/wrappers/jruby-1.7.1/ruby
    </Location>
</VirtualHost>

<VirtualHost *:80>
    # This Flask web app will use Python 3.0
    PassengerPython /usr/bin/python3.0
    ServerName www.baz.com
    DocumentRoot /webapps/baz/public
</VirtualHost>
------------------------------

include::users_guide_snippets/rvm_helper_tool.txt[]

=== PassengerPython <filename> ===
:version: 4.0.0
include::users_guide_snippets/since_version.txt[]

This option allows one to specify the Python interpreter to use. See <<PassengerRuby,PassengerRuby>> for more information. The default value is 'python', meaning that the Python interpreter will be looked up according to the `PATH` environment variable.

[[PassengerAppRoot]]
=== PassengerAppRoot <path/to/root> ===
By default, Phusion Passenger assumes that the application's root directory
is the parent directory of the 'public' directory. This option allows one to
specify the application's root independently from the DocumentRoot, which
is useful if the 'public' directory lives in a non-standard place.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once.

Example:

-----------------------------
<VirtualHost test.host>
    DocumentRoot /var/rails/zena/sites/example.com/public
    PassengerAppRoot /var/rails/zena   # <-- normally Phusion Passenger would
                                       #     have assumed that the application
                                       #     root is "/var/rails/zena/sites/example.com"
</VirtualHost>
-----------------------------

[[PassengerSpawnMethod]]
=== PassengerSpawnMethod <string> ===
[TIP]
."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:

************************************************
If your application works on Mongrel or Thin, but not on Phusion Passenger, then set
`PassengerSpawnMethod` to 'direct'. Otherwise, leave it at 'smart' (the default).
************************************************

However, we do recommend you to try to understand it. The 'smart' spawn
method bring many benefits.
=========================================================

include::users_guide_snippets/passenger_spawn_method.txt[]

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.

In each place, it may be specified at most once. The default value is 'smart'.

[[PassengerLoadShellEnvvars]]
=== passengerLoadShellEnvvars <on|off> ===
:version: 4.0.20
include::users_guide_snippets/since_version.txt[]

Enables or disables the loading of shell environment variables before spawning the application.

If this option is turned on, and the user's shell is `bash`, then applications are loaded by running them with `bash -l -c`. Otherwise, they are loaded by running them directly from the `PassengerHelperAgent` process.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. The default value is 'on'.

[[PassengerEnabled]]
=== PassengerEnabled <on|off> ===
You can set this option to 'off' to completely disable Phusion Passenger for
a certain location. This is useful if, for example, you want to integrate a PHP
application into the same virtual host as a Rails application.

Suppose that you have a Rails application in '/apps/foo'. Suppose that you've
dropped Wordpress -- a blogging application written in PHP -- in
'/apps/foo/public/wordpress'. You can then configure Phusion Passenger as
follows:

------------------------------------
<VirtualHost *:80>
    ServerName www.foo.com
    DocumentRoot /apps/foo/public
    <Directory /apps/foo/public/wordpress>
        PassengerEnabled off
        AllowOverride all      # <-- Makes Wordpress's .htaccess file work.
    </Directory>
</VirtualHost>
------------------------------------

This way, Phusion Passenger will not interfere with Wordpress.

'PassengerEnabled' may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess'.

In each place, it may be specified at most once. The default value is 'on'.

[[PassengerTempDir]]
=== PassengerTempDir <directory> ===
Specifies the directory that Phusion Passenger should use for storing temporary
files. This includes things such as Unix socket files, buffered file uploads
(see also <<PassengerUploadBufferDir,PassengerUploadBufferDir>>), etc.

This option may be specified once, in the global server configuration. The
default temp directory that Phusion Passenger uses is '/tmp'.

This option is especially useful if Apache is not allowed to write to /tmp
(which is the case on some systems with strict SELinux policies) or if the
partition that /tmp lives on doesn't have enough disk space.

.Command line tools
Some Phusion Passenger command line administration tools, such as
`passenger-status`, must know what Phusion Passenger's temp directory is
in order to function properly. You can pass the directory through the
`PASSENGER_TMPDIR` environment variable, or the `TMPDIR` environment variable
(the former will be used if both are specified).

For example, if you set 'PassengerTempDir' to '/my_temp_dir', then invoke
`passenger-status` after you've set the `PASSENGER_TMPDIR` or `TMPDIR`
environment variable, like this:

----------------------------------------------------------
export PASSENGER_TMPDIR=/my_temp-dir
sudo -E passenger-status
# The -E option tells 'sudo' to preserve environment variables.
----------------------------------------------------------

[[PassengerUploadBufferDir]]
=== PassengerUploadBufferDir <directory> ===
Phusion Passenger buffers large file uploads to disk in order prevent slow file
uploads from blocking web applications. By default, a subdirectory in the
system's temporary files directory (or a subdirectory in the directory specified
in <<PassengerTempDir,PassengerTempDir>>, if set) is automatically created for
storing these buffered file uploads.

This configuration directive allows you to specify a different directory for storing
buffered file uploads. If you've specified such a directory (as opposed to using
Phusion Passenger's default) then you *must* ensure that this directory exists.

This configuration directive is also useful if you're using apache2-mpm-itk.
The buffered file upload directory that Phusion Passenger creates by default has
very strict permissions: it can only be accessed by the Apache worker processes.
However, Phusion Passenger assumes that all Apache worker processes are running
as the same user. apache2-mpm-itk breaks this assumption by running multiple
Apache worker processes as different users. So if you're using apace2-mpm-itk,
you should set this option to a directory that is writable by all Apache worker
processes, such as '/tmp'.

You may specify 'PassengerUploadBufferDir' in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverrides Options` is enabled.

In each place, it may be specified at most once.

=== PassengerRestartDir <directory> ===
As described in the deployment chapters of this document, Phusion Passenger
checks the file 'tmp/restart.txt' in the applications'
<<application_root,root directory>> for restarting applications. Sometimes it
may be desirable for Phusion Passenger to look in a different directory instead,
for example for security reasons (see below). This option allows you to
customize the directory in which 'restart.txt' is searched for.

You may specify 'PassengerRestartDir' in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverrides Options` is enabled.

In each place, it may be specified at most once.

You can either set it to an absolute directory, or to a directory relative to
the <<application_root,application root>>. Examples:

-----------------------------------
<VirtualHost *:80>
    ServerName www.foo.com
    # Phusion Passenger will check for /apps/foo/public/tmp/restart.txt
    DocumentRoot /apps/foo/public
</VirtualHost>

<VirtualHost *:80>
    ServerName www.bar.com
    DocumentRoot /apps/bar/public
    # An absolute filename is given; Phusion Passenger will
    # check for /restart_files/bar/restart.txt
    PassengerRestartDir /restart_files/bar
</VirtualHost>

<VirtualHost *:80>
    ServerName www.baz.com
    DocumentRoot /apps/baz/public
    # A relative filename is given; Phusion Passenger will
    # check for /apps/baz/restart_files/restart.txt
    #
    # Note that this directory is relative to the APPLICATION ROOT, *not*
    # the value of DocumentRoot!
    PassengerRestartDir restart_files
</VirtualHost>
-----------------------------------

.What are the security reasons for wanting to customize PassengerRestartDir?
Touching restart.txt will cause Phusion Passenger to restart the application.
So anybody who can touch restart.txt can effectively cause a Denial-of-Service
attack by touching restart.txt over and over. If your web server or one of your
web applications has the permission to touch restart.txt, and one of them has a
security flaw which allows an attacker to touch restart.txt, then that will
allow the attacker to cause a Denial-of-Service.

You can prevent this from happening by pointing PassengerRestartDir to a
directory that's readable by Apache, but only writable by administrators.

[[PassengerRollingRestarts]]
=== PassengerRollingRestarts <on|off> ===
:version: 3.0.0
include::users_guide_snippets/enterprise_only.txt[]

Enables or disables support for rolling restarts. Normally when you
restart an application (by touching restart.txt), Phusion Passenger would
shut down all application processes and spawn a new one. The spawning
of a new application process could take a while, and any requests that
come in during this time will be blocked until this first application
process has spawned.

But when rolling restarts are enabled, Phusion Passenger Enterprise will:

1. Spawn a new process in the background.
2. When it's done spawning, Phusion Passenger Enterprise will replace one of the old processes with this newly spawned one.
3. Step 1 and 2 are repeated until all processes have been replaced.

This way, visitors will not experience any delays when you are restarting your application. This allows you to, for example, upgrade your application often without degrading user experience.

Rolling restarts have a few caveat however that you should be aware of:

- Upgrading an application sometimes involves upgrading the database schema.
  With rolling restarts, there may be a point in time during which processes
  belonging to the previous version and processes belonging to the new version
  both exist at the same time. Any database schema upgrades you perform must
  therefore be backwards-compatible with the old application version.
- Because there's no telling which process will serve a request, users may
  not see changes brought about by the new version until all processes have
  been restarted. It is for this reason that you should not use rolling
  restarts in development, only in production.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. The default value is 'off'.

=== PassengerResistDeploymentErrors <on|off> ===
:version: 3.0.0
include::users_guide_snippets/enterprise_only.txt[]

Enables or disables resistance against deployment errors.

Suppose you've upgraded your application and you've issues a command to restart it (by touching restart.txt), but the application code contains an error that prevents Phusion Passenger from successfully spawning a process (e.g. a syntax error). Phusion Passenger would normally display an error message in response to this.

By enabling deployment error resistance, Phusion Passenger Enterprise would instead do this:

- It passes the request to one of the existing application processes (that belong to the previous version of the application). The visitor will not see a Phusion Passenger process spawning error message.
- It logs the error to the global web server error log file.
- It sets an internal flag so that no processes for this application will be spawned (even when the current traffic would normally result in more processes being spawned) and no processes will be idle cleaned. Processes *could* still be shutdown because of other events, e.g. because their <<PassengerMemoryLimit,memory limit>> have been reached.

This way, visitors will suffer minimally from deployment errors. Phusion Passenger will attempt to restart the application again next time restart.txt is touched.

Enabling deployment error resistance only works if <<PassengerRollingRestarts,rolling restart>> is also enabled.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. The default value is 'off'.

=== Security options ===

[[PassengerUserSwitching]]
==== PassengerUserSwitching <on|off> ====
Whether to enable <<user_switching,user switching support>>.

This option may only occur once, in the global server configuration.
The default value is 'on'.

[[PassengerUser]]
==== PassengerUser <username> ====
If <<user_switching,user switching support>> is enabled, then Phusion Passenger will
by default run the web application as the owner of the file 'config/environment.rb'
(for Rails apps) or 'config.ru' (for Rack apps). This option allows you to override
that behavior and explicitly set a user to run the web application as, regardless
of the ownership of 'environment.rb'/'config.ru'.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.

In each place, it may be specified at most once.

[[PassengerGroup]]
==== PassengerGroup <group name> ====
If <<user_switching,user switching support>> is enabled, then Phusion Passenger will
by default run the web application as the primary group of the owner of the file
'config/environment.rb' (for Rails apps) or 'config.ru' (for Rack apps). This option
allows you to override that behavior and explicitly set a group to run the web application
as, regardless of the ownership of 'environment.rb'/'config.ru'.

'<group name>' may also be set to the special value '!STARTUP_FILE!', in which case
the web application's group will be set to 'environment.rb'/'config.ru''s group.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.

In each place, it may be specified at most once.

[[PassengerDefaultUser]]
==== PassengerDefaultUser <username> ====
Phusion Passenger enables <<user_switching,user switching support>> by default.
This configuration option allows one to specify the user that 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'.

[[PassengerDefaultGroup]]
==== PassengerDefaultGroup <group name> ====
Phusion Passenger enables <<user_switching,user switching support>> by default.
This configuration option allows one to specify the group that 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 the primary group of the user specifified by
<<PassengerDefaultUser,PassengerDefaultUser>>.

[[PassengerFriendlyErrorPages]]
==== PassengerFriendlyErrorPages <on|off> ====
Phusion Passenger can display friendly error pages whenever an application fails
to start. This friendly error page presents the startup error message, some
suggestions for solving the problem, and a backtrace. This feature is very useful
during application development and useful for less experienced system administrators,
but the page might reveal potentially sensitive information, depending on the
application. Experienced system administrators who are using Phusion Passenger
on serious production servers should consider turning this feature off.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. The default value is 'on'.


=== Resource control and optimization options ===

[[PassengerMaxPoolSize]]
==== PassengerMaxPoolSize <integer> ====
The maximum number of <<application_process,application processes>> that may
simultaneously exist. A larger number results in higher memory usage,
but improves the ability to handle concurrent HTTP requests.

The optimal value depends on your system's hardware and your workload. You can learn more at the Phusion article link:http://blog.phusion.nl/2013/03/12/tuning-phusion-passengers-concurrency-settings/[Tuning Phusion Passenger's concurrency settings].

If you find that your server is running out of memory then you should lower this value.

This option may only occur once, in the global server configuration.
The default value is '6'.

[[PassengerMinInstances]]
==== PassengerMinInstances <integer> ====
This specifies the minimum number of application processes that should exist for a
given application. You should set this option to a
non-zero value if you want to avoid potentially long startup times after a website
has been <<idle_process,idle>> for an extended period.

Please note that this option does *not* pre-start application processes during Apache
startup. It just makes sure that when the application is first accessed:

1. at least the given number of processes will be spawned.
2. the given number of processes will be kept around even when processes are being
   idle cleaned (see <<PassengerPoolIdleTime,PassengerPoolIdleTime>>).

If you want to pre-start application processes during Apache startup, then you should use the <<PassengerPreStart,PassengerPreStart>> directive, possibly in combination with
'PassengerMinInstances'. This behavior might seem counter-intuitive at first sight,
but <<PassengerPreStart,PassengerPreStart>> explains the rationale behind it.

For example, suppose that you have the following configuration:

---------------------------------
PassengerMaxPoolSize 15
PassengerPoolIdleTime 10

<VirtualHost *:80>
    ServerName foobar.com
    DocumentRoot /webapps/foobar/public
    PassengerMinInstances 3
</VirtualHost>
---------------------------------

When you start Apache, there are 0 application processes for 'foobar.com'. Things will
stay that way until someone visits 'foobar.com'. Suppose that there is only 1 visitor.
1 application process will be started immediately to serve the visitor, while 2 will
be spawned in the background. After 10 seconds, when the idle timeout has
been reached, these 3 application processes will not be cleaned up.

Now suppose that there's a sudden spike of traffic, and 100 users visit 'foobar.com'
simultanously. Phusion Passenger will start 12 more application processes. After the idle
timeout of 10 seconds have passed, Phusion Passenger will clean up 12 application
processes, keeping 3 processes around.

The PassengerMinInstances option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Limits` is on.

In each place, it may be specified at most once. The default value is '1'.

[[PassengerMaxInstances]]
==== PassengerMaxInstances <integer> ====
:version: 3.0.0
include::users_guide_snippets/enterprise_only.txt[]

The maximum number of application processes that may simultaneously exist
for an 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,PassengerMaxPoolSize>>. A value of 0
means that there is no limit placed on the number of processes a single application
may spawn, i.e. only the global limit of <<PassengerMaxPoolSize,PassengerMaxPoolSize>>
will be enforced.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.

In each place, it may be specified at most once. The default value is '0'.

.Practical usage example
[TIP]
===========================================================================
Suppose that you're hosting two web applications on your server, a personal
blog and an e-commerce website. You've set <<PassengerMaxPoolSize,PassengerMaxPoolSize>>
to 10. The e-commerce website is more important to you. You can then set
'PassengerMaxInstances' to 3 for your blog, so that it will never spawn more
than 3 processes, even if it suddenly gets a lot of traffic. Your e-commerce website
on the other hand will be free to spawn up to 10 processes if it gets a lot of traffic.
===========================================================================

==== PassengerMaxInstancesPerApp <integer> ====
The maximum number of application processes that may simultaneously exist
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,PassengerMaxPoolSize>>. A value of 0
means that there is no limit placed on the number of processes a single application
may use, i.e. only the global limit of <<PassengerMaxPoolSize,PassengerMaxPoolSize>>
will be enforced.

This option may only occur once, in the global server configuration.
The default value is '0'.

.Practical usage example
[TIP]
===========================================================================
Suppose that you're hosting two blogs (blog A and B) on your server, and that
you've set <<PassengerMaxPoolSize,PassengerMaxPoolSize>> to 10. Under normal
circumstances, if blog A suddenly gets a lot of traffic, then A will use all 10
pool slots. If blog B suddenly gets some traffic, then it will only be able to
use 1 pool slot (forcefully releasing 1 slot from A) until A's traffic has
settled down and it has released more pool slots.

If you consider both blogs equally important, then you can set
'PassengerMaxInstancesPerApp' to 5. This way, both blogs will never use more
than 5 pool slots.
===========================================================================

.Relation with PassengerMaxInstances
[NOTE]
===========================================================================
Unlike <<PassengerMaxInstances,PassengerMaxInstances>>, this configuration
option is global and applies to all applications. 'PassengerMaxInstances' on the
other hand is per-virtual host.

Suppose that you're hosting two web applications on your server, a personal
blog and an e-commerce website. You've set <<PassengerMaxPoolSize,PassengerMaxPoolSize>>
to 10. The e-commerce website is more important to you. You can then set
'PassengerMaxInstances' to 3 for your blog, so that it will never use more than
3 pool slots, even if it suddenly gets a lot of traffic. Your e-commerce website
on the other hand will be free to use up all 10 slots if it gets a lot of traffic.

In summary, 'PassengerMaxInstancesPerApp' divides the pool equally among the
different web applications, while 'PassengerMaxInstances' allows one to divide
the pool unequally, according to each web application's relative importance.
===========================================================================

[[PassengerPoolIdleTime]]
==== PassengerPoolIdleTime <integer> ====
The maximum number of seconds that an application process may be idle. That is,
if an application process 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.

When this value is set to '0', application processes will not be shutdown unless 
it's really necessary, i.e. when Phusion Passenger is out of application processes
for a given application and one of the <<inactive_process,inactive application processes>> needs to
make place for another application process. Setting the value to 0 is
recommended if you're on a non-shared host that's only running a few
applications, each which must be available at all times.

This option may only occur once, in the global server configuration.
The default value is '300'.

[[PassengerMaxPreloaderIdleTime]]
==== PassengerMaxPreloaderIdleTime <integer> ====
The ApplicationSpawner server (explained in <<spawning_methods_explained,Spawning
methods explained>>) has an idle timeout, just like the backend processes spawned by
Phusion Passenger do. That is, it will automatically shutdown if it hasn't done
anything for a given period.

This option allows you to set the ApplicationSpawner server's idle timeout, in
seconds. A value of '0' means that it should never idle timeout.

Setting a higher value will mean that the ApplicationSpawner server is kept around
longer, which may slightly increase memory usage. But as long as the
ApplicationSpawner server is running, the time to spawn a Ruby on Rails backend
process only takes about 10% of the time that is normally needed, assuming that
you're using the 'smart' or 'smart-lv2' <<PassengerSpawnMethod,spawning method>>. So if your
system has enough memory, is it recommended that you set this option to a high
value or to '0'.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.

In each place, it may be specified at most once. The default value is '300' (5 minutes).

==== PassengerStartTimeout <seconds> ====
:version: 4.0.15
include::users_guide_snippets/since_version.txt[]

Specifies a timeout for the startup of application processes. If an application process fails to start within the timeout period then it will be forcefully killed with SIGKILL, and the error will be logged.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Limits` is on.

In each place, it may be specified at most once. The default value is '90'.

[[PassengerConcurrencyModel]]
==== PassengerConcurrencyModel <process|thread> ====
:version: 4.0.0
include::users_guide_snippets/enterprise_only.txt[]

Specifies the I/O concurrency model that should be used for application processes. Phusion Passenger supports two concurrency models:

 * 'process' - single-threaded, multi-processed I/O concurrency. Each application process only has a single thread and can only handle 1 request at a time. This is the concurrency model that Ruby applications traditionally used. It has excellent compatiblity (can work with applications that are not designed to be thread-safe) but is unsuitable for workloads in which the application has to wait for a lot of external I/O (e.g. HTTP API calls), and uses more memory because each process has a large memory overhead.
 * 'thread' - multi-threaded, multi-processed I/O concurrency. Each application process has multiple threads (customizable via <<PassengerThreadCount,PassengerThreadCount>>). This model provides much better I/O concurrency and uses less memory because threads share memory with each other within the same process. However, using this model may cause compatibility problems if the application is not designed to be thread-safe.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess'.

In each place, it may be specified at most once. The default value is 'process'.

[[PassengerThreadCount]]
==== PassengerThreadCount <number> ====
:version: 4.0.0
include::users_guide_snippets/enterprise_only.txt[]

Specifies the number of threads that Phusion Passenger should spawn per application process. This option only has effect if <<PassengerConcurrencyModel,PassengerConcurrencyModel>> is 'thread'.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess'.

In each place, it may be specified at most once. The default value is '1'.

[[PassengerMaxRequests]]
==== PassengerMaxRequests <integer> ====
The maximum number of requests an application process will process. After
serving that many requests, the application process will be shut down and
Phusion Passenger will restart it. A value of 0 means that there is no maximum:
an application process will thus be shut down when its idle timeout has been
reached.

This option is useful if your application is leaking memory. By shutting
it down after a certain number of requests, all of its memory is guaranteed
to be freed by the operating system.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Limits` is on.

In each place, it may be specified at most once. The default value is '0'.

[CAUTION]
=====================================================
The <<PassengerMaxRequests,PassengerMaxRequests>> directive should be considered
as a workaround for misbehaving applications. It is advised that you fix the
problem in your application rather than relying on these directives as a
measure to avoid memory leaks.
=====================================================

[[PassengerMaxRequestTime]]
==== PassengerMaxRequestTime <seconds> ====
:version: 3.0.0
include::users_guide_snippets/enterprise_only.txt[]

The maximum amount of time, in seconds, that an application process may take
to process a request. If the request takes longer than this amount of time,
then the application process will be forcefully shut down, and possibly
restarted upon the next request. A value of 0 means that there is no time limit.

This option is useful for preventing your application from freezing for an
indefinite period of time.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Limits` is on.

In each place, it may be specified at most once. The default value is '0'.

.Example
Suppose that most of your requests are known to finish within 2 seconds.
However, there is one URI, '/expensive_computation', which is known to take up
to 10 seconds. You can then configure Phusion Passenger as follows:

----------------------------------------------
<VirtualHost *:80>
    ServerName www.example.com
    DocumentRoot /webapps/my_app/public
    
    PassengerMaxRequestTime 2
    <Location /expensive_computation>
        PassengerMaxRequestTime 10
    </Location>
</VirtualHost>
----------------------------------------------

If a request to '/expensive_computation' takes more than 10 seconds,
or if a request to any other URI takes more than 2 seconds,
then the corresponding application process will be forced to shutdown.

[CAUTION]
=====================================================
The <<PassengerMaxRequestTime,PassengerMaxRequestTime>> directive should be
considered as a workaround for misbehaving applications. It is advised that you
fix the problem in your application rather than relying on these directives as a
measure to avoid freezing applications.
=====================================================

[[PassengerMemoryLimit]]
==== PassengerMemoryLimit <integer> ====
:version: 3.0.0
include::users_guide_snippets/enterprise_only.txt[]

The maximum amount of memory that an application process may use, in megabytes.
Once an application process has surpassed its memory limit, it will process
all the requests currently present in its queue and then shut down.
A value of 0 means that there is no maximum: the application's memory usage
will not be checked.

This option is useful if your application is leaking memory. By shutting
it down, all of its memory is guaranteed to be freed by the operating system.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Limits` is on.

In each place, it may be specified at most once. The default value is '0'.

[NOTE]
.A word about permissions
=====================================================
The <<PassengerMemoryLimit,PassengerMemoryLimit>> directive uses
`ps` command to query memory usage information. On Linux, it further
queries `/proc` to obtain additional memory usage information that's
not obtainable through `ps`. You should ensure that the `ps` works
correctly and that the `/proc` filesystem is accessible by the
`PassengerHelperAgent` process.
=====================================================

[CAUTION]
=====================================================
The <<PassengerMaxRequests,PassengerMaxRequests>> and
<<PassengerMemoryLimit,PassengerMemoryLimit>> directives should be considered
as workarounds for misbehaving applications. It is advised that you fix the
problem in your application rather than relying on these directives as a
measure to avoid memory leaks.
=====================================================

==== PassengerStatThrottleRate <integer> ====
By default, Phusion Passenger performs several filesystem checks (or, in
programmers jargon, 'stat() calls') each time a request is processed:

- It checks whether 'config/environment.rb', 'config.ru' or 'passenger_wsgi.py'
  is present, in order to autodetect Rails, Rack and WSGI applications.
- It checks whether 'restart.txt' has changed or whether 'always_restart.txt'
  exists, in order to determine whether the application should be restarted.

On some systems where disk I/O is expensive, e.g. systems where the harddisk is
already being heavily loaded, or systems where applications are stored on NFS
shares, these filesystem checks can incur a lot of overhead.

You can decrease or almost entirely eliminate this overhead by setting
'PassengerStatThrottleRate'. Setting this option to a value of 'x' means that
the above list of filesystem checks will be performed at most once every 'x'
seconds. Setting it to a value of '0' means that no throttling will take place,
or in other words, that the above list of filesystem checks will be performed on
every request.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Limits` is on.

In each place, it may be specified at most once. The default value is '0'.

[[PassengerPreStart]]
==== PassengerPreStart <url> ====
By default, Phusion Passenger does not start any application processes until said
web application is first accessed. The result is that the first visitor of said
web application might experience a small delay as Phusion Passenger is starting
the web application on demand. If that is undesirable, then this directive can be
used to pre-started application processes during Apache startup.

A few things to be careful of:

- This directive accepts the *URL* of the web application you want to pre-start,
  not a on/off value! This might seem a bit weird, but read on for rationale. As
  for the specifics of the URL:
  * The domain part of the URL must be equal to the value of the 'ServerName'
    directive of the VirtualHost block that defines the web application.
  * Unless the web application is deployed on port 80, the URL should contain
    the web application's port number too.
  * The path part of the URL must point to some URI that the web application
    handles.
- You will probably want to combine this option with
  <<PassengerMinInstances,PassengerMinInstances>> because application processes
  started with 'PassengerPreStart' are subject to the usual idle timeout rules.
  See the example below for an explanation.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.

In each place, it may be specified any number of times.

===== Example 1: basic usage =====

Suppose that you have the following web applications.

---------------------------
<VirtualHost *:80>
   ServerName foo.com
   DocumentRoot /webapps/foo/public
</VirtualHost>

<VirtualHost *:3500>
   ServerName bar.com
   DocumentRoot /webapps/bar/public
</VirtualHost>
---------------------------

You want both of them to be pre-started during Apache startup. The URL for
foo.com is 'http://foo.com/' (or, equivalently, 'http://foo.com:80/') and
the URL for bar.com is 'http://bar.com:3500/'. So we add two PassengerPreStart
directives, like this:

---------------------------
<VirtualHost *:80>
   ServerName foo.com
   DocumentRoot /webapps/foo/public
</VirtualHost>

<VirtualHost *:3500>
   ServerName bar.com
   DocumentRoot /webapps/bar/public
</VirtualHost>

PassengerPreStart http://foo.com/           # <--- added
PassengerPreStart http://bar.com:3500/      # <--- added
---------------------------

===== Example 2: pre-starting apps that are deployed in sub-URIs =====

Suppose that you have a web application deployed in a sub-URI '/store', like this:

---------------------------
<VirtualHost *:80>
   ServerName myblog.com
   DocumentRoot /webapps/wordpress
   RailsBaseURI /store
</VirtualHost>
---------------------------

Then specify the domain name of its containing virtual host followed by the sub-URI,
like this:

---------------------------
<VirtualHost *:80>
   ServerName myblog.com
   DocumentRoot /webapps/wordpress
   RailsBaseURI /store
</VirtualHost>

PassengerPreStart http://myblog.com/store    # <----- added
---------------------------

The sub-URI *must* be included; if you don't then the directive will have no effect.
The following example is wrong and won't pre-start the store web application:

---------------------------
PassengerPreStart http://myblog.com/    # <----- WRONG! Missing "/store" part.
---------------------------

===== Example 3: combining with PassengerMinInstances =====

Application processes started with PassengerPreStart are
also subject to the idle timeout rules as specified by
<<PassengerPoolIdleTime,PassengerPoolIdleTime>>! That means that by default,
the pre-started application processes for foo.com are bar.com are shut down
after a few minutes of inactivity. If you don't want that to happen, then
you should combine PassengerPreStart with
<<PassengerMinInstances,PassengerMinInstances>>, like this:

---------------------------
<VirtualHost *:80>
   ServerName foo.com
   DocumentRoot /webapps/foo/public
   # Added!
   PassengerMinInstances 1
</VirtualHost>

<VirtualHost *:3500>
   ServerName bar.com
   DocumentRoot /webapps/bar/public
   # Added!
   PassengerMinInstances 1
</VirtualHost>

PassengerPreStart http://foo.com/
PassengerPreStart http://bar.com:3500/
---------------------------

===== So why a URL? Why not just an on/off flag? =====

A directive that accepts a simple on/off flag is definitely more intuitive,
but due technical difficulties w.r.t. the way Apache works, it's very hard
to implement it like that:

- It is very hard to obtain a full list of web applications defined in the
  Apache configuration file(s). In other words, it's hard for Phusion Passenger
  to know which web applications are deployed on Apache until a web application
  is first accessed, and without such a list Phusion Passenger wouldn't know
  which web applications to pre-start. It's probably not completely impossible
  to obtain such a list, but this brings us to the following point;
- Users expect things like 'mod_env' to work even in combination with Phusion
  Passenger. For example some people put ``SetEnv PATH=....'' in their virtual
  host block and they expect the web application to pick that environment variable
  up when it's started. Information like this is stored in module-specific
  locations that Phusion Passenger cannot access directly. Even if the previous
  bullet point is solved and we can obtain a list of web applications,
  we cannot start the application with the correct mod_env information.
  mod_env is just one such example; there are probably many other Apache modules,
  all of which people expect to work, but we cannot answer to those expectations
  if PassengerPreStart is implemented as a simple on/off flag.

So as a compromise, we made it accept a URL. This is easier to implement for
us and altough it looks weird, it behaves consistently w.r.t. cooperation
with other Apache modules.

===== What does Phusion Passenger do with the URL? =====

During Apache startup, Phusion Passenger will send a dummy HEAD request to the
given URL and discard the result. In other words, Phusion Passenger simulates a
web access at the given URL. However this simulated request is always sent to
localhost, *not* to the IP that the domain resolves to. Suppose that bar.com
in example 1 resolves to 209.85.227.99; Phusion Passenger will
send the following HTTP request to 127.0.0.1 port 3500 (and not to 209.85.227.99
port 3500):

----------------------
HEAD / HTTP/1.1
Host: bar.com
Connection: close
----------------------

Similarly, for example 2, Phusion Passenger will send the following HTTP request
to 127.0.0.1 port 80:

----------------------
HEAD /store HTTP/1.1
Host: myblog.com
Connection: close
----------------------

===== Do I need to edit /etc/hosts and point the domain in the URL to 127.0.0.1? =====

No. See previous subsection.

===== My web application consists of multiple web servers. What URL do I need to specify, and in which web server's Apache config file? =====

Put the web application's virtual host's ServerName value and the virtual host's
port in the URL, and put
PassengerPreStart on all machines that you want to pre-start the web application
on. The simulated web request is always sent to 127.0.0.1, with the domain name
in the URL as value for the 'Host' HTTP header, so you don't need to worry about
the request ending up at a different web server in the cluster.

===== Does PassengerPreStart support https:// URLs? =====

Yes. And it does not perform any certificate validation.

[[PassengerHighPerformance]]
==== PassengerHighPerformance <on|off> ====
By default, Phusion Passenger is compatible with mod_rewrite and most other
Apache modules. However, a lot of effort is required in order to be compatible.
If you turn 'PassengerHighPerformance' to 'on', then Phusion Passenger will be
a little faster, in return for reduced compatibility with other Apache modules.

In places where 'PassengerHighPerformance' is turned on, mod_rewrite rules will
likely not work. mod_autoindex (the module which displays a directory index)
will also not work. Other Apache modules may or may not work, depending on what
they exactly do. We recommend you to find out how other modules behave in high
performance mode via testing.

This option is *not* an all-or-nothing global option: you can enable high
performance mode for certain virtual hosts or certain URLs only.
The 'PassengerHighPerformance' option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess'.

In each place, it may be specified at most once. The default value is 'off',
so high performance mode is disabled by default, and you have to explicitly
enable it.

.When to enable high performance mode?

If you do not use mod_rewrite or other Apache modules then it might make
sense to enable high performance mode.

It's likely that some of your applications depend on mod_rewrite or other
Apache modules, while some do not. In that case you can enable high performance
for only those applications that don't use other Apache modules. For example:

------------------------------------
<VirtualHost *:80>
    ServerName www.foo.com
    DocumentRoot /apps/foo/public
    .... mod_rewrite rules or options for other Apache modules here ...
</VirtualHost>

<VirtualHost *:80>
    ServerName www.bar.com
    DocumentRoot /apps/bar/public
    PassengerHighPerformance on
</VirtualHost>
------------------------------------

In the above example, high performance mode is only enabled for www.bar.com.
It is disabled for everything else.

If your application generally depends on mod_rewrite or other Apache modules,
but a certain URL that's accessed often doesn't depend on those other modules,
then you can enable high performance mode for a certain URL only. For example:

------------------------------------
<VirtualHost *:80>
    ServerName www.foo.com
    DocumentRoot /apps/foo/public
    .... mod_rewrite rules or options for other Apache modules here ...
    
    <Location /chatroom/ajax_update_poll>
        PassengerHighPerformance on
    </Location>
</VirtualHost>
------------------------------------

This enables high performance mode for
http://www.foo.com/chatroom/ajax_update_poll only.


/////////////////////////////////////////
/////////////////////////////////////////


=== Connection handling options ===

[[PassengerBufferResponse]]
==== PassengerBufferResponse <on|off> ====
When turned on, application-generated responses are buffered by Apache. Buffering will
happen in memory.

Before we proceed with explaining this configuration option, we want to state the following to avoid confusion. If you use Phusion Passenger for Apache, there are in fact two response buffering systems active:

1. The Apache response buffering system. `PassengerBufferResponse` turns this on or off.
2. The Phusion Passenger response buffering system, a.k.a. 'real-time disk-backed response buffering'. This buffering system is always on, regardless of the value of `PassengerBufferResponse`.

Response buffering is useful because it protects against slow HTTP clients that do not read responses immediately or quickly enough. Buffering prevents such slow clients from blocking web applications that have limited concurrency. Because Phusion Passenger's response buffering is always turned on, you are always protected. Therefore, `PassengerBufferResponse` is off by default, and you never should have to turn it on.

If for whatever reason you want to turn Apache-level response buffering on, you can do so with this option.

Apache's response buffering works differently from Phusion Passenger's. Apache's buffering system buffers the entire response before attempting to send it to the client, while Phusion Passenger's attempts to send the data to the client immediately. Therefore, if you turn on `PassengerBufferResponse`, you may interfere with applications that want to stream responses to the client.
Apache's version also buffers to memory only, making it problematic for large responses. Phusion Passenger's version buffers to disk when the response exceeds a certain threshold.

How does response buffering - whether it's done by Apache or by Phusion Passenger - exactly protect against slow clients?
Consider an HTTP client that's on a dial-up modem link, and your
application process generates a 2 MB response. If the response is buffered
then your application process will be blocked until the entire 2 MB has been
sent out to the HTTP client. This disallows your application process to do any useful
work in the mean time. By buffering responses, Phusion Passenger or Apache will read
the application response as quickly as possible and will take care of forwarding the data
to slow clients.

So keep in mind that enabling `passenger_buffering_response` will make streaming responses
impossible. Consider for example this piece of Rails code:

--------------------------------
render :text => lambda { |response, output|
    10.times do |i|
        output.write("entry #{i}\n")
        output.flush
        sleep 1
    end
}
--------------------------------

...or this piece of Rack code:

--------------------------------
class Response
    def each
        10.times do |i|
            yield("entry #{i}\n")
            sleep 1
        end
    end
end

app = lambda do |env|
    [200, { "Content-Type" => "text/plain" }, Response.new]
end
--------------------------------

When `PassengerBufferResponse` is turned on, Apache will wait until
the application is done sending the entire response before forwarding it
to the client. The client will not receive anything for 10 seconds,
after which it receives the entire response at once.
When `PassengerBufferResponse` is turned off, it works as expected: the client
receives an "entry X" message every second for 10 seconds.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess'.

In each place, it may be specified at most once. The default value is 'off'.

[NOTE]
=====================================================
The <<PassengerBufferResponse,PassengerBufferResponse>> directive should be turned off
if responses can be huge. Because entire responses are buffered in memory when turned on.
=====================================================

[[PassengerMaxRequestQueueSize]]
==== passenger_max_request_queue_size <number> ====
:version: 4.0.15
include::users_guide_snippets/since_version.txt[]

When all application processes are already handling their maximum number of concurrent requests, Phusion Passenger will queue all incoming requests. This option specifies the maximum size for that queue. If the queue is already at this specified limit, then Phusion Passenger will immediately send a "503 Service Unavailable" error to any incoming requests.

A value of 0 means that the queue is unbounded.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess'.

In each place, it may be specified at most once. The default value is '100'.


=== Compatibility options ===

[[PassengerResolveSymlinksInDocumentRoot]]
==== PassengerResolveSymlinksInDocumentRoot <on|off> ====
Configures whether Phusion Passenger should resolve symlinks in the document root.
Please refer to <<application_detection,How Phusion Passenger detects whether a
virtual host is a web application>> for more information.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. It is off by default.

==== PassengerAllowEncodedSlashes <on|off> ====
By default, Apache doesn't support URLs with encoded slashes (%2f), e.g. URLs like
this: `/users/fujikura%2fyuu`. If you access such an URL then Apache will return a
404 Not Found error. This can be solved by turning on PassengerAllowEncodedSlashes
as well as Apache's
link:http://httpd.apache.org/docs/2.0/mod/core.html#allowencodedslashes[AllowEncodedSlashes].

Is it important that you turn on both AllowEncodedSlashes *and* PassengerAllowEncodedSlashes,
otherwise this feature will not work properly.

PassengerAllowEncodedSlashes may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. It is off by default.

Please note however that turning on support for encoded slashes will break support for
mod_rewrite passthrough rules. Because of bugs/limitations in Apache, Phusion Passenger
can support either encoded slashes or mod_rewrite passthrough rules, but not both at the
same time. Luckily this option can be specified anywhere, so you can enable it only for
virtual hosts or URLs that need it:

----------------------------------
<VirtualHost *:80>
    ServerName www.example.com
    DocumentRoot /webapps/example/public
    AllowEncodedSlashes on
    RewriteEngine on
    
    # Check for maintenance file and redirect all requests
    RewriteCond %{DOCUMENT_ROOT}/system/maintenance.html -f
    RewriteCond %{SCRIPT_FILENAME} !maintenance.html
    RewriteRule ^.*$ /system/maintenance.html [L]
    
    # Make /about an alias for /info/about.
    RewriteRule ^/about$ /info/about [PT,L]
    
    <Location ~ "^/users/">
        # In a location block so that it doesn't interfere with the
        # above /about mod_rewrite rule.
        PassengerAllowEncodedSlashes on
    </Location>
</VirtualHost>
----------------------------------

With this, http://www.example.com/users/fujikura%2fyuu will work properly, and
accessing http://www.example.com/about will properly display the result of
http://www.example.com/info/about. Notice that PassengerAllowEncodedSlashes only
interferes with passthrough rules, not with any other mod_rewrite rules. The rules for
displaying maintenance.html will work fine even for URLs starting with "/users".


=== Logging and debugging options ===

[[PassengerLogLevel]]
==== PassengerLogLevel <integer> ====
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'.

==== PassengerDebugLogFile <filename> ====
By default Phusion Passenger debugging and error messages are written to the global
web server error log. This option allows one to specify the file that debugging and
error messages should be written to instead.

This option may only occur once, in the global server configuration.

==== PassengerDebugger <on|off> ====
:version: 3.0.0
include::users_guide_snippets/enterprise_only.txt[]

Turns support for application debugging on or off. In case of Ruby applications,
turning this option on will cause them to load the `ruby-debug` gem (when on Ruby 1.8),
the `debugger` gem (when on Ruby 1.9) or the `byebug` gem (when on Ruby 2.0). If you're
using Bundler, you should add this to your Gemfile:

-------------------------------------------
gem 'ruby-debug', :platforms => :ruby_18
gem 'debugger', :platforms => :ruby_19
gem 'byebug', :platforms => :ruby_20
-------------------------------------------

Once debugging is turned on, you can use the command `passenger-irb --debug <PID>` to attach an rdebug console to the application process with the given PID. Attaching will succeed once the application process executes a `debugger` command.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. The default value is 'off'.


=== Classic Ruby on Rails (<= 2.x)-specific options ===

These options only have effect on classic Ruby on Rails 1.x and 2.x applications.
Ruby on Rails >= 3.x applications are considered Rack applications.

[[RailsBaseURI]]
==== RailsBaseURI <uri> ====
Used to specify that the given URI is a Rails application. See
<<deploying_rails_to_sub_uri,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 following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

[[rails_env]]
==== RailsEnv <string> ====
This option allows one to specify the default `RAILS_ENV` value.

This option may occur in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. The default value is 'production'.

=== Rack and Rails >= 3 specific options ===

[[RackBaseURI]]
==== RackBaseURI <uri> ====
Used to specify that the given URI is a Rack application. See
<<deploying_rack_to_sub_uri,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 following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

[[rack_env]]
==== RackEnv <string> ====
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 in the following places:

 * In the global server configuration.
 * In a virtual host configuration block.
 * In a `<Directory>` or `<Location>` block.
 * In '.htaccess', if `AllowOverride Options` is on.

In each place, it may be specified at most once. The default value is 'production'.

=== Deprecated or removed options ===

The following options have been deprecated, but are still supported for backwards
compatibility reasons.

==== RailsRuby ====
Deprecated in favor of <<PassengerRuby,PassengerRuby>>.

==== RailsUserSwitching ====
Deprecated in favor of <<PassengerUserSwitching,PassengerUserSwitching>>.

==== RailsDefaultUser ====
Deprecated in favor of <<PassengerDefaultUser,PassengerDefaultUser>>.

==== RailsAllowModRewrite ====
This option doesn't do anything anymore in recent versions of Phusion Passenger.

==== RailsSpawnMethod ====
Deprecated in favor of <<PassengerSpawnMethod,PassengerSpawnMethod>>.

==== RailsAutoDetect, RackAutoDetect and WsgiAutoDetect ====
These options have been removed in version 4.0.0 as part of an optimization. You should use <<PassengerEnabled,PassengerEnabled>> instead.

==== RailsAppSpawnerIdleTime ====
This option has been removed in version 4.0.0, and replaced with <<PassengerMaxPreloaderIdleTime,PassengerMaxPreloaderIdleTime>>.

==== RailsFrameworkSpawnerIdleTime ====
This option is no longer available in version 4.0.0. There is no alternative because framework spawning has been removed altogether. You should use smart spawning instead.



[[troubleshooting]]
== Troubleshooting ==

=== Operating system-specific problems ===

==== MacOS X: The installer cannot locate MAMP's Apache ====

.Symptoms
*******************************************************************************
The installer finds Apache 2 development headers at `/Applications/MAMP/Library/bin/apxs`.
However, Apache cannot be found. The installer also outputs the following error:
------------------------------------
cannot open /Applications/MAMP/Library/build/config_vars.mk:
No such file or directory at /Applications/MAMP/Library/bin/apxs line 218.
------------------------------------
*******************************************************************************

Your MAMP installation seems to be broken. In particular, 'config_vars.mk' is missing.
Please read link:http://forum.mamp.info/viewtopic.php?t=1866[this forum topic] to learn how
to fix this problem.

See also link:http://code.google.com/p/phusion-passenger/issues/detail?id=12[this bug report].


=== Problems during installation ===

[[installing_ruby_dev]]
==== Ruby development headers aren't installed ====

.Symptoms
*******************************************************************************
Installing Phusion Passenger fails because of one of the following errors:

- The Phusion Passenger installer tells you that the Ruby development headers
  aren't installed.
- The error message ``'no such file to load -- mkmf''' occurs.
- The error message ``'ruby.h: No such file or directory''' occurs.
*******************************************************************************

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:

Ubuntu/Debian::
	Please type:
+
-----------------------------------------
sudo apt-get install ruby1.8-dev
-----------------------------------------

Fedora/CentOS/RHEL::
	Please type:
+
-----------------------------------------
su -c 'yum install ruby-devel'
-----------------------------------------

FreeBSD::
	Please install Ruby from 'ports' or with `pkg_add`. If that fails,
	please install Ruby from source.

MacOS X::
	Please install Ruby from source.

Other operating systems::
	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.

NOTE: 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_ruby_installation,Specifying the correct Ruby installation>>.

==== Apache development headers aren't installed ====

.Symptoms
*******************************************************************************
Installing Phusion Passenger fails because of one of the following errors:

- The installer says that the Apache development headers aren't installed.
- The error message ``'httpd.h: No such file or directory''' occurs.
+
(Instead of 'httpd.h', the message might also be 'http_config.h' or something
else similar to 'http_*.h'.)
*******************************************************************************

Ubuntu::
	Please type:
+
-----------------------------------------
sudo apt-get install apache2-prefork-dev
-----------------------------------------

Debian::
	Please type:
+
-----------------------------------------
sudo apt-get install apache2-dev
-----------------------------------------

Fedora/CentOS/RHEL::
	Please type:
+
--------------------------------
su -c 'yum install httpd-devel'
--------------------------------

FreeBSD::
	Please install Apache from 'ports' or with `pkg_add`. If that fails,
	please install Apache from source.

MacOS X::
	Please install Apache from source.

Other operating systems::
	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.


==== APR development headers aren't installed ====

.Symptoms
*******************************************************************************
Installing Phusion Passenger fails because one of the following errors:

- The installer tells you that APR development headers aren't installed.
- The error message ``'apr_pools.h: No such file or directory''' occurs.
- The error message ``'apr_strings.h: No such file or directory''' occurs.
*******************************************************************************

Ubuntu::
	Please type:
+
-----------------------------------------
sudo apt-get install libapr1-dev
-----------------------------------------

Debian::
	Please type:
+
-----------------------------------------
sudo apt-get install libapr1-dev
-----------------------------------------

Fedora/CentOS/RHEL::
	Please type:
+
--------------------------------
su -c 'yum install apr-devel'
--------------------------------

Other Linux distributions::
	Please consult your distribution's package database. There should be a
	package which provides APR development headers.

Other operating systems::
	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.


==== Phusion Passenger is using the wrong Apache during installation ====

Please <<specifying_correct_apache_install,Specifying the correct Apache
installation>>, and re-run the Phusion Passenger installer.


==== Phusion Passenger is using the wrong Ruby during installation ====

Please <<specifying_ruby_installation,Specifying the correct Ruby
installation>>, and re-run the Phusion Passenger installer.


=== Problems after installation ===

[TIP]
.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.
=====================================================

==== My Rails application works on Mongrel, but not on Phusion Passenger ====

Please try setting <<PassengerSpawnMethod,PassengerSpawnMethod>> to 'conservative'.

==== Phusion Passenger has been compiled against the wrong Apache installation ====

.Symptoms
*******************************************************************************
Apache crashes during startup (after being daemonized). The Apache error log
says ``'seg fault or similar nasty error detected in the parent process'''.
*******************************************************************************

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 <<specifying_correct_apache_install,specify the
correct Apache installation>>, and <<install_passenger,reinstall Phusion
Passenger>>.

==== I get a "403 Forbidden" error ====

See next subsection.

==== Static assets such as images and stylesheets aren't being displayed ====

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:

1. 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 link:http://groups.google.com/group/phusion-passenger/browse_thread/thread/9699a639a87f85f4/b9d71a03bf2670a5[this discussion].

2. 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.

==== The Apache error log says that the spawn manager script does not exist, or that it does not have permission to execute it ====

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.

==== The Rails application reports that it's unable to start because of a permission error ====

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,RailsDefaultUser>>, if that's
specified).

Please read <<user_switching,User switching (security)>> for details.

==== My Rails application's log file is not being written to ====

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,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,User switching (security)>> for details.

If you're using a RedHat-derived Linux distribution (such as Fedora or CentOS)
then it is link:http://code.google.com/p/phusion-passenger/issues/detail?id=4[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
-----------------------------------------------------------

==== I've deployed my app on SSL, but the app thinks its not on SSL ====

Rails and many other frameworks infers whether it's running on SSL through the CGI
environment variable `HTTPS`. Apache always sets this variable when on SSL,
except when SSL is incorrectly configured.

Most Apache installations already configure SSL by default on port 443
(conf/extra/httpd-ssl.conf). Some people think they can save some typing in
subsequent SSL vhost blocks, and omit important options like 'SSLEngine on',
like this:

--------------------------------------
# httpd-ssl.conf contains something like:
# <VirtualHost _default_:443>
#     SSLEngine on
#     ...
# </VirtualHost>
Include conf/extra/httpd-ssl.conf

<VirtualHost *:443>
    ServerName www.example.com
    DocumentRoot /webapps/example/public
</Virtualhost>
--------------------------------------

*This is wrong!* In each SSL vhost block you must re-specify all the SSL options.
Otherwise Apache won't properly detect the vhost as an SSL vhost block. Here's
the corrected example:

--------------------------------------
Include conf/extra/httpd-ssl.conf

<VirtualHost *:443>
    ServerName www.example.com
    DocumentRoot /webapps/example/public
    SSLEngine on
    ...more SSL options here...
</Virtualhost>
--------------------------------------


[[conflicting_apache_modules]]
=== Conflicting Apache modules ===

==== mod_userdir ====

'mod_userdir' is not compatible with Phusion Passenger at the moment.

==== MultiViews (mod_negotiation) ====

MultiViews is not compatible with Phusion Passenger. You should disable MultiViews
for all Phusion Passenger hosts.

==== VirtualDocumentRoot ====

VirtualDocumentRoot is not compatible with Phusion Passenger at the moment.


== Analysis and system maintenance ==

include::users_guide_snippets/analysis_and_system_maintenance.txt[]


== Tips ==

include::users_guide_snippets/tips.txt[]

=== X-Sendfile support ===

Phusion Passenger does not provide X-Sendfile support by itself. Please install
link:http://tn123.ath.cx/mod_xsendfile/[mod_xsendfile] for X-Sendfile support.

=== Upload progress ===

Phusion Passenger does not provide upload progress support by itself. Please
try drogus's link:http://github.com/drogus/apache-upload-progress-module/tree/master[
Apache upload progress module] instead.


== Under the hood ==
Phusion Passenger hides a lot of complexity for the end user (i.e. the web server
system administrator), but sometimes it is desirable to know what is going on.
This section describes a few things that Phusion Passenger does under the hood.

include::users_guide_snippets/under_the_hood/page_caching_support.txt[]
include::users_guide_snippets/under_the_hood/relationship_with_ruby.txt[]

=== Static assets serving ===
Phusion Passenger accelerates serving of static files. This means that, if an URI
maps to a file that exists, then Phusion Passenger will let Apache serve that file
directly, without hitting the web application.

Phusion Passenger does all this without the need for any mod_rewrite rules. People
who are switching from an old Mongrel-based setup might have mod_rewrite rules such
as these:

------------------------------------------------------------
# Check whether this request has a corresponding file; if that
# exists, let Apache serve it, otherwise forward the request to
# Mongrel.
RewriteCond %{DOCUMENT_ROOT}/%{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ balancer://mongrel%{REQUEST_URI} [P,QSA,L]
------------------------------------------------------------

These kind of mod_rewrite rules are no longer required, and you can safely remove
them.

[[application_detection]]
=== How Phusion Passenger detects whether a virtual host is a web application ===
After you've read the deployment instructions you might wonder how Phusion Passenger
knows that the DocumentRoot points to a web application that Phusion Passenger is
able to serve, and how it knows what kind of web application it is (e.g. Rails or Rack).

Phusion Passenger checks whether the virtual host is a Rails application by checking
whether the following file exists:

------------------------------------------------
dirname(DocumentRoot) + "/config/environment.rb"
------------------------------------------------

If you're not a programmer and don't understand the above pseudo-code snippet, it means
that Phusion Passenger will:

1. Extract the parent directory filename from the value of the DocumentRoot directory.
2. Append the text "/config/environment.rb" to the result, and check whether the resulting
   filename exists.

So suppose that your document root is '/webapps/foo/public'. Phusion Passenger will check
whether the file '/webapps/foo/config/environment.rb' exists.

Note that Phusion Passenger does *not* resolve any symlinks in the document root path by
default since version 2.2.0 -- in contrast to versions earlier than 2.2.0, which do resolve
symlinks.
So for example, suppose that your DocumentRoot points to '/home/www/example.com', which in
turn is a symlink to '/webapps/example.com/public'. In versions earlier than 2.2.0, Phusion
Passenger will check whether '/webapps/example.com/config/environment.rb' exists because it
resolves all symlinks. Phusion Passenger 2.2.0 and later however will check for
'/home/www/config/environment.rb'. This file of course doesn't exist, and as a result Phusion
Passenger will not activate itself for this virtual host, and you'll most likely see an Apache
mod_dirindex directory listing.

If you need the old symlink-resolving behavior for whatever reason, then you can turn on
<<PassengerResolveSymlinksInDocumentRoot,PassengerResolveSymlinksInDocumentRoot>>.

Another way to solve this situation is to explicitly tell Phusion Passenger what the
correct application root is through the <<PassengerAppRoot,PassengerAppRoot>> configuration
directive.

Autodetection of Rack applications happens through the same mechanism, exception that
Phusion Passenger will look for 'config.ru' instead of 'config/environment.rb'.


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include::users_guide_snippets/appendix_b_terminology.txt[]

include::users_guide_snippets/appendix_c_spawning_methods.txt[]

include::users_guide_snippets/environment_variables.txt[]