mod-wsgi 4.5.10

Installer for Apache/mod_wsgi.

Overview

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.

System Requirements

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.

Installation into Apache

For installation directly into your Apache installation using the CMMI method, see the full documentation at:

• http://www.modwsgi.org/

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.

Installation into Python

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.

Non standard Apache installations

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.

Running mod_wsgi-express as root

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.

Using mod_wsgi-express with Django

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.

Connecting into Apache installation

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.