The mod_wsgi package provides an Apache module that implements a WSGI compliant interface for hosting Python based web applications on top of the Apache web server.
Installation of mod_wsgi from source code can be performed in one of two ways.
The first way of installing mod_wsgi is the traditional way that has been
used by many software packages. This is where it is installed as a module
directly into your Apache installation using the commands configure,
make and make install, a method sometimes referred to by the
acyronym CMMI.
The second and newest way of installing mod_wsgi is to install it as a
Python package into your Python installation using the Python pip
install command.
This newer way of installing mod_wsgi will compile not only the Apache module for mod_wsgi, but will also install a Python module and admin script for starting up a standalone instance of Apache directly from the command line with an auto generated configuration.
This later mechanism for installing mod_wsgi using Python pip is a much
simpler way of getting starting with hosting your Python web application.
In particular, the new installation method makes it very easy to use
Apache/mod_wsgi in a development environment without the need to perform
any Apache configuration yourself.
The Apache module for mod_wsgi created when using the pip install
method can still be used with the main Apache installation, via manual
configuration if necessary.
On some platforms, this latter method is actually the only option supported
when using the operating system supplied Apache installation. For example,
in MacOS X Sierra, Apple has completely broken the ability to install third
party Apache modules using the apxs tool normally used for this task.
History suggests that Apple will never fix the problem as they have broken
things in the past in other ways and workarounds were required as they
never fixed those problems either. This time there is no easy workaround as
they no longer supply certain tools which are required to perform the
installation.
With either installation method for mod_wsgi, you must have Apache installed. This must be a complete Apache installation. It is not enough to have only the runtime packages for Apache installed. You must have the corresponding development package for Apache installed, which contains the Apache header files, as these are required to be able compile and install third party Apache modules.
Similarly with Python, you must have a complete Python installation which includes the corresponding development package, which contains the header files for the Python library.
If you are running Debian or Ubuntu Linux with Apache 2.2 system packages, and were using the Apache prefork MPM you would need both:
- apache2-mpm-prefork
- apache2-prefork-dev
If instead you were using the Apache worker MPM, you would need both:
- apache2-mpm-worker
- apache2-threaded-dev
If you are running Debian or Ubuntu Linux with Apache 2.4 system packages, regardless of which Apache MPM is being used, you would need both:
- apache2
- apache2-dev
If you are running RHEL, CentOS or Fedora, you would need both:
- httpd
- httpd-devel
If you are using the Software Collections Library (SCL) packages with RHEL, CentOS or Fedora, you would need:
- httpd24
If you are running MacOS X, you will need to have the Xcode command line
tools installed. These can be installed by running xcode-select --install.
For installation directly into your Apache installation using the CMMI method, see the full documentation at:
Alternatively, use the following instructions to install mod_wsgi into your Python installation and then either copy the mod_wsgi module into your Apache installation, or configure Apache to use the mod_wsgi module from the Python installation.
When using this approach, you will still need to manually configure Apache to have mod_wsgi loaded into Apache, and for it to know about your WSGI application.
To install the mod_wsgi directly into your Python installation, from within the source directory of the mod_wsgi package you can run:
python setup.py install
This will compile mod_wsgi and install the resulting package into your Python installation.
If wishing to install an official release direct from the Python Package Index (PyPi), you can instead run:
pip install mod_wsgi
If you wish to use a version of Apache which is installed into a non
standard location, you can set and export the APXS environment variable
to the location of the Apache apxs script for your Apache installation
before performing the installation.
Note that nothing will be copied into your Apache installation at this point. As a result, you do not need to run this as the root user unless installing it into a site wide Python installation rather than a Python virtual environment. It is recommended you always use Python virtual environments and never install any Python package direct into the system Python installation.
To verify that the installation was successful, run the mod_wsgi-express
script with the start-server command:
mod_wsgi-express start-server
This will start up Apache/mod_wsgi on port 8000. You can then verify that the installation worked by pointing your browser at:
http://localhost:8000/
When started in this way, the Apache web server will stay in the foreground. To stop the Apache server, use CTRL-C.
For a simple WSGI application contained in a WSGI script file called
wsgi.py, in the current directory, you can now run:
mod_wsgi-express start-server wsgi.py
This instance of the Apache web server will be completely independent of, and will not interfere with any existing instance of Apache you may have running on port 80.
If you already have another web server running on port 8000, you can
override the port to be used using the --port option:
mod_wsgi-express start-server wsgi.py --port 8080
For a complete list of options you can run:
mod_wsgi-express start-server --help
For further information related to using mod_wsgi-express see the main
mod_wsgi documentation.
Many Linux distributions have a tendency to screw around with the standard
Apache Software Foundation layout for installation of Apache. This can
include renaming the Apache httpd executable to something else, and in
addition to potentially renaming it, replacing the original binary with a
shell script which performs additional actions which can only be performed
as the root user.
In the case of the httpd executable simply being renamed, the
executable will obviously not be found and mod_wsgi-express will fail
to start at all.
In this case you should work out what the httpd executable was renamed
to and use the --httpd-executable option to specify its real location.
For example, if httpd was renamed to apache2, you might need to use:
mod_wsgi-express start-server wsgi.py --httpd-executable=/usr/sbin/apache2
In the case of the httpd executable being replaced with a shell script
which performs additional actions before then executing the original
httpd executable, and the shell script is failing in some way, you will
need to use the location of the original httpd executable the shell
script is in turn executing.
The primary intention of mod_wsgi-express is to make it easier for
users to run up Apache on non privileged ports, especially during the
development of a Python web application. If you want to be able to run
Apache using mod_wsgi-express on a privileged port such as the standard
port 80 used by HTTP servers, then you will need to run
mod_wsgi-express as root. In doing this, you will need to perform
additional steps.
The first thing you must do is supply the --user and --group
options to say what user and group your Python web application should run
as. Most Linux distributions will pre define a special user for Apache to
run as, so you can use that. Alternatively you can use any other special
user account you have created for running the Python web application:
mod_wsgi-express start-server wsgi.py --port=80 \
--user www-data --group www-data
This approach to running mod_wsgi-express will be fine so long as you
are using a process supervisor which expects the process being run to remain
in the foreground and not daemonize.
If however you are directly integrating into the system init scripts where
separate start and stop commands are expected, with the executing process
expected to be daemonized, then a different process is required to setup
mod_wsgi-express.
In this case, instead of simply using the start-server command to
mod_wsgi-express you should use setup-server:
mod_wsgi-express setup-server wsgi.py --port=80 \
--user www-data --group www-data \
--server-root=/etc/mod_wsgi-express-80
In running this command, it will not actually startup Apache. All it will do is create the set of configuration files and the startup script to be run.
So that these are not created in the default location of a directory under
/tmp, you should use the --server-root option to specify where they
should be placed.
Having created the configuration and startup script, to start the Apache instance you can now run:
/etc/mod_wsgi-express-80/apachectl start
To subsequently stop the Apache instance you can run:
/etc/mod_wsgi-express-80/apachectl stop
You can also restart the Apache instance as necessary using:
/etc/mod_wsgi-express-80/apachectl restart
Using this approach, the original options you supplied to setup-server
will be cached with the same configuration used each time. If you need to
update the set of options, run setup-server again with the new set of
options.
Note that even taking all these steps, it is possible that running up
Apache as root using mod_wsgi-express may fail on systems where
SELinux extensions are enabled. This is because the SELinux profile may not
match what is being expected for the way that Apache is being started, or
alternatively, the locations that Apache has been specified as being
allowed to access, don't match where the directory specified using the
--server-root directory was placed. You may therefore need to configure
SELinux or move the directory used with --server-root to an allowed
location.
To use mod_wsgi-express with Django, after having installed the
mod_wsgi package into your Python installation, edit your Django settings
module and add mod_wsgi.server to the list of installed apps.
INSTALLED_APPS = (
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'mod_wsgi.server',
)
To prepare for running mod_wsgi-express, ensure that you first collect
up any Django static file assets into the directory specified for them in
the Django settings file:
python manage.py collectstatic
You can now run the Apache server with mod_wsgi hosting your Django application by running:
python manage.py runmodwsgi
If working in a development environment and you would like to have any code
changes automatically reloaded, then you can use the --reload-on-changes
option.
python manage.py runmodwsgi --reload-on-changes
If wanting to have Apache started as root in order to listen on port 80,
instead of using mod_wsgi-express setup-server as described above,
use the --setup-only option to the runmodwsgi management command.
python manage.py runmodwsgi --setup-only --port=80 \
--user www-data --group www-data \
--server-root=/etc/mod_wsgi-express-80
This will setup all the required files and you can use apachectl to
start and stop the Apache instance as explained previously.
If you want to use mod_wsgi in combination with your system Apache installation, the CMMI method for installing mod_wsgi would normally be used. If you are on MacOS X Sierra that is no longer possible. Even prior to MacOS X Sierra, the System Integrity Protection (SIP) system of MacOS X, prevented installing the mod_wsgi module into the Apache modules directory.
The CMMI installation method also involves a bit more work as you need to
separately download the mod_wsgi source code, run the configure tool
and then run make and make install.
The alternative to using the CMMI installation method is to use the Apache
mod_wsgi module created by running pip install. This can be directly
referenced from the Apache configuration, or copied into the Apache modules
directory.
To use the Apache mod_wsgi module from where pip install placed it,
run the command mod_wsgi-express module-config. This will output
something like:
LoadModule wsgi_module /usr/local/lib/python2.7/site-packages/mod_wsgi/server/mod_wsgi-py27.so WSGIPythonHome /usr/local/lib
These are the directives needed to configure Apache to load the mod_wsgi module and tell mod_wsgi where the Python installation directory or virtual environment was located.
This would be placed in the Apache httpd.conf file, or if the Linux
distribution separates out module configuration into a mods-available
directory, in the wsgi.load file within the mods-available
directory. In the latter case where a mods-available directory is used,
the module would then be enabled by running a2enmod wsgi as root.
If necessary Apache can then be restarted to verify the module is loading
correctly. You can then configure Apache as necessary for your specific
WSGI application.
Note that because in this scenario the mod_wsgi module for Apache could be
located in a Python virtual environment, if you destroy the Python virtual
environment the module will also be deleted. In that case you would need to
ensure you recreated the Python virtual environment and reinstalled the
mod_wsgi package using pip, or take out the mod_wsgi configuration from
Apache before restarting Apache or it will fail to startup.
Instead of referencing the mod_wsgi module from the Python installation,
you can instead copy the mod_wsgi module into the Apache installation. To
do that, run the mod_wsgi-express install-module command, running it as
root if necessary. This will output something like:
LoadModule wsgi_module modules/mod_wsgi-py27.so WSGIPythonHome /usr/local/lib
This is similar to above except that the mod_wsgi module was copied to the
Apache modules directory first and the LoadModule directive references
it from that location. You should take these lines and configure Apache in
the same way as described above. Do note that copying the module like this
will not work on recent versions of MacOS X due to the SIP feature of MacOS X.