Python Django

juju deploy python-django

14.04 LTS

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Python-django Charm

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What is Django?

Django is a high-level web application framework that loosely follows the model-view-controller (MVC) design pattern. Python's equivalent to Ruby on Rails, Django lets you build complex data-driven websites quickly and easily - Django focuses on automating as much as possible and adhering to the "Don't Repeat Yourself" (DRY) principle. Django additionally emphasizes reusability and "pluggability" of components; many generic third-party "applications" are available to enhance projects or to simply reduce development time even further.

Notable features include:

  • An object-relational mapper (ORM)
  • Automatic admin interface
  • Elegant URL dispatcher
  • Form serialization and validation system
  • Templating system
  • Lightweight, standalone web server for development and testing
  • Internationalization support
  • Testing framework and client

The charm

This charm will install Django. It can also install your Django project and its dependencies from either a template or from a version control system.

It can also link your project to a database and sync the schemas. This charm also comes with a Fabric fabfile to interact with the deployment in a cloud-aware manner.

Quick start

Simply:

juju bootstrap
juju deploy python-django

juju deploy postgresql
juju add-relation python-django postgresql:db

juju deploy gunicorn
juju add-relation python-django gunicorn
juju expose python-django

In a couple of minutes, your new (vanilla) Django site should be ready at the public address of gunicorn. You can find it in the output of the juju status command.

This is roughtly equivalent to the Creating a project step in Django's tutorial.

Example: Deploying using a site template
  1. Setup your Django specific parameters in mydjangosite.yaml like this one:

     mydjangosite:
         project_template_url: https://github.com/xenith/django-base-template/zipball/master
         project_template_extension: py,md,rst
    
  2. Deployment with Gunicorn:

     juju bootstrap
     juju deploy --config mydjangosite.yaml mydjangosite
    
     juju deploy postgresql
     juju add-relation mydjangosite postgresql:db
    
     juju deploy gunicorn
     juju add-relation mydjangosite gunicorn
     juju expose mydjangosite
    
Example: Deploying using a code repository
  1. Setup your Django specific parameters in mydjangosite.yaml like this one:

     mydjangosite:
         vcs: bzr
         repos_url: lp:~patrick-hetu/my_site
    
  2. Deployment with Gunicorn:

     juju bootstrap
     juju deploy --config mydjangosite.yaml python-django mydjangosite
    
     juju deploy postgresql
     juju add-relation mydjangosite postgresql:db
    
     juju deploy gunicorn
     juju add-relation mydjangosite gunicorn
     juju expose mydjangosite
    
  3. Your new Django site should be accessible at the public address of Gunicorn. To find it, look for it in the output of the juju status command.

Project layout and code injection

Continuing from the previous example, your web site should be on the Django node at:

/srv/mydjangosite/

As you can see there the charm has injected some code at the end of your settings.py file (or created it if it was not there) to be able to import what's in the juju_settings/ directory.

It's recommended that you make your vcs ignore database and secret files or any files that have information that you don't want to publish.

Complex configuration example: dpaste

mydpastesite:
  django_version: ''
  django_south: True
  django_south_version: ''
  vcs: 'git'
  repos_url: 'https://github.com/bartTC/dpaste.git'
  repos_branch: '2.6'
  application_path: 'dpaste'
  django_settings: 'dpaste.settings'
  settings_injection_path: 'settings/__init__.py'
  urls_injection_path: 'urls/__init__.py'
  requirements_pip_files: 'requirements.txt'
  additional_distro_packages: "python-imaging,python-tz,python-dev,build-essential,libpq-dev,libmysqlclient-dev,libxml2-dev,libxslt1-dev"

Upgrade the charm

This charm allow you to upgrade your deployment using Juju's upgrade-charm command. This command will:

  • upgrade Django
  • upgrade additional pip packages
  • upgrade additional Debian packages
  • upgrade using requirements files in your project

Management with Fabric

Fabric is a Python (2.5 or higher) library and command-line tool for streamlining the use of SSH for application deployment or system administration tasks.

It provides a basic suite of operations for executing local or remote shell commands (normally or via sudo) and uploading/downloading files, as well as auxiliary functionality such as prompting the running user for input, or aborting execution.

This charm includes a Fabric script that use Juju's information to perform various tasks.

For a list of tasks type this command after bootstraping your Juju environment:

fab -l

For example, with a python-django service deployed you can run commands on all of its units:

fab -R python-django pull
[10.0.0.2] Executing task 'pull'
[10.0.0.2] run: bzr pull lp:~my_name/django_code/my_site
...
[10.0.0.2] run: invoke-rc.d gunicorn restart
...

Or you can also run commands on a single unit:

fab -R python-django/0 manage:createsuperuser
...
[10.0.0.2] out: Username (leave blank to use 'ubuntu'):

Limitation:

  • You can only execute tasks for one role at a time. But it can be a service or unit.

If you want to extend the fabfile check out fabtools.

Ansible

See: https://github.com/cmars/juju-ansible

Security

Note that if you're using a requirement.txt file the packages will be downloaded with pip and it doesn't do any cryptographic verification of its downloads.

Writing application charm

To create an application subordinate charm that can be related to this charm you need to at least define an interface named directory-path in your metadate.yaml file like this:

[...]
requires:
  python-django:
    interface: directory-path
    scope: container
    optional: true

When you add a relation between your charm and the python-django charm, you will be able to get those relation variables from the hook:

  • settings_dir_path
  • urls_dir_path
  • django_admin_cmd
  • install_root

Now your charm will be informed about where it needs to add new settings and urls files and how to run additionnal Django commands. The Django charm reloads Gunicorn after the relation to catch the changes.

Changelog

X: Not yet released
  • Python3 compatibility
  • Support for Django 1.7
  • Support for virtualenv
  • Tests
  • More vcs options
  • More pip options
6: Notable changes:
  • The charm now use charm-helpers for hooks
  • The chams now use ansible for installation
  • Mysql and Redis and rabbitmq (celery) support was added
  • The charm can install South and do migrations
  • The charm include a Fabric and Ansible scripts to interact with Juju

Note that I still need to think about the role of Fabric, Ansible, Salt, charm-helpers, etc

Configuration changes:

  • python_path now accept multiple path separated by commas
  • requirements_pip_files now also accept urls
  • requirements_pip_files and requirements_apt_files are empty by default
  • settings_secret_key_path was renamed settings_secret_key_name
  • settings_database_path was renamed settings_database_name

New options:

  • unit_config
  • settings_amqp_name
  • celery_always_eager
  • django_south
  • django_south_version
  • django_debug
  • django_allowed_host
  • django_extra_settings
  • settings_injection_path
  • url_injection_path
  • pip_extra_args

Backwards incompatible changes:

  • Some default options changed so be sure to checkout your configuration files.
  • The use of Ansible change a bit how things are done now be sure to test.
3: Notable changes:
  • Rewrite the charm using python instead of BASH scripts
  • Django projects now need no modification to work with the charm
  • Use the django-admin startproject command with configurable arguments if no repos is specified
  • Juju's generated settings and urls files are now added in a juju_settings and a juju_urls directories by default
  • New MongoDB relation (server side is yet to be done)
  • New upgrade hook that upgrade pip and debian packages
  • Expose ports is now handle by the charm

Configuration changes:

  • default user and group is now ubuntu
  • new install_root option
  • new django_version option
  • new additional_pip_packages option
  • new repos_branch,repos_username,repos_password options
  • new project_name, project_template_extension, project_template_url options
  • new urls_dir_name and settings_dir_name options
  • new project_template_url and project_template_extension options
  • database, uploads, static, secret and cache settings locations are now configurable
  • extra_deb_pkg was renamed additional_distro_packages
  • requirements was renamed requirements_pip_files and now support multiple files
  • if python_path is empty set as install_root

Backwards incompatible changes:

  • swift support was moved to a subordinate charm
  • postgresql relation hook was rename pgsql instead of db
2: Notable changes:
  • You can configure all wsgi (Gunicorn) settings via the config.yaml file
  • Juju compatible Fabric fabfile.py is included for PAAS commands
  • Swift storage backend is now optional

Backwards incompatible changes:

  • Use split settings and urls
  • Permissons are now based on WSGI's user and group instead of just being www-data
  • media and static files are now in new directories ./uploads and ./static/
  • Deprecated configuration variables: site_domain, site_username, site_password, site_admin_email
1: Notable changes:
  • Initial release

Inspiration