python django #1

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Description

This charm will install Django. It can also install your Django
project and his 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 come with a Fabric fabfile to interact with the
deployement in a cloud aware manner.

Python-django Charm

Authors:

What is Django?

Django is a high-level web application framework that loosely follows
the model-view-controller 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 to 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 his 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 come with a Fabric fabfile to interact with the
deployement 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 minute, 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 site a 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

Note: If your using juju-core you must remove the first line
of the file and the indentation for the rest of the file.

  1. 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 code repository

  1. Setup your Django specific parameters in mydjangosite.yaml like this one::

    mydjangosite:
    vcs: bzr
    repos_url: lp:~patrick-hetu/my_site

Note:

If your using juju-core you must remove the first line
of the file and the indentation for the rest of the file.

  1. Deployment with Gunicorn::
    juju bootstrap
juju deploy --config mydjangosite.yaml 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

Note: If your using juju-core you must add --upload-tools to the
juju bootstrap command.

  1. Accessing your new Django site should be ready 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

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

/srv/python-django/

As you can see there the charm have inject 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 to make your vcs to ignore database and secret files or
any files that have information that you don't want to be publish.

Upgrade the charm

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

  • upgrade Django
  • upgrade additionnal pip packages
  • upgrade additionnal 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 systems
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 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 task for one role at the time.
    But it can be a service or unit.

If you want to extend the fabfile check out fabtools.

Security

Note that if your 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
at least to 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 will add a relation between your charm and the python-django charm
the hook you will be able to get those relation variables:

  • settings_dir_path
  • urls_dir_path
  • django_admin_cmd
  • install_root

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

Changelog

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

Configuration

additional_distro_packages
(string) Comma separated extra packages to install.
python-imaging,python-docutils,python-tz
additional_pip_packages
(string) Comma separated extra packages to install.
application_path
(string) The relative path to install_root where the manage.py script is located.
django_settings
(string) The Python path to your Django settings module.
settings
django_version
(string) Version or origin from which to install. May be one of the following: distro (default), ppa:somecustom/ppa, a deb url sources entry or a valid pip line like 'Django' or 'Django==1.5' or a reposiroty url (without the -e).
distro
install_root
(string) The root directory to checkout to.
/srv/
listen_ip
(string) IP adresses that Gunicorn will listen on. By default we listen on all of them.
0.0.0.0
port
(int) Port the application will be listenning.
8080
project_template_extension
(string) When Django copies the project template files, it also renders certain files through the template engine: the files whose extensions match the --extension option (py by default) and the files whose names are passed with the --name option.
project_template_url
(string) If not repository url is found, the charm will create a new project. This option is the --template argument value for the startproject command to use a custom project template. Django will also accept URLs (http, https, ftp) to compressed archives with the app template files, downloading and extracting them on the fly. For more informations see: https://docs.djangoproject.com/en/dev/ref/django-admin/#startproject-projectname-destination
python_path
(string) Set an additionnal PYTHONPATH to the project.
repos_branch
(string) The repo branch to pull out from. If empty, it will pull out the default branch or trunk (such as origin/master with git). Note that this setting only applies to git. This option is not supported for hg. For svn and bzr, specify the branch name as part of the URL.
repos_password
(string) The vcs password. Note: *Subversion only* settings. For other vcs use the repos_url for auth.
repos_url
(string) The vcs url to checkout.
repos_username
(string) The vcs user name. Note: *Subversion only* settings. For other vcs use the repos_url for auth.
requirements_apt_files
(string) Comma separated relative paths to requirement files. Note that the charm won't manually upgrade packages defined in this file. Set the variable to an empty string if you don't want the feature.
requirements.apt
requirements_pip_files
(string) Comma separated relative paths to requirement files. Note that the charm won't manually upgrade packages defined in this file. Set the variable to an empty string if you don't want the feature.
requirements.txt,requirements.pip
settings_database_path
(string) The place where the database configuration will be appended or written. Set the variable to an empty string if you don't want the feature.
juju_settings/20-engine-%(engine_name)s.py
settings_dir_name
(string) The place where the generated settings will be written. Set the variable to an empty string if you don't want the feature.
juju_settings
settings_secret_key_path
(string) The place where the secret key configuration will be appended or written. Set the variable to an empty string if you don't want the feature.
juju_settings/10-secret.py
site_secret_key
(string) The web site secret key. Leave empty will generate one. NOTE: You **NEED** to set this in a multi-units architecture or you will have some trouble.
urls_dir_name
(string) The place where the generated urls will be written. Set the variable to an empty string if you don't want the feature.
juju_urls
vcs
(string) The vcs software to use. Only hg, git, bzr, and svn are currently supported.
wsgi_access_logfile
(string) The Access log file to write to.
wsgi_access_logformat
(string) The Access log format. Don't forget to escape all quotes and round brackets.
wsgi_backlog
(int) The maximum number of pending connections.
2048
wsgi_extra
(string) Space separated extra settings. For example: --debug
wsgi_group
(string) Switch worker process to run as this group. A valid group id (as an int) or the name.
www-data
wsgi_keep_alive
(int) Keep alive time in seconds.
2
wsgi_log_file
(string) The log file to write to. If empty the logs would be handle by upstart.
-
wsgi_log_level
(string) The granularity of Error log outputs.
info
wsgi_max_requests
(int) The maximum number of requests a worker will process before restarting.
wsgi_timeout
(int) Timeout of a request in seconds.
30
wsgi_timestamp
(string) The variable to modify to trigger Gunicorn reload.
wsgi_umask
(string) A bit mask for the file mode on files written by Gunicorn. The number 0 means Python guesses the base. Note that this affects unix socket permissions.
0
wsgi_user
(string) Switch worker processes to run as this user. User id (as an int) or the name.
www-data
wsgi_worker_class
(string) Gunicorn workers type. Can be: sync, eventlet, gevent, tornado
sync
wsgi_worker_connections
(int) The maximum number of simultaneous clients.
1000
wsgi_workers
(int) The number of worker process for handling requests. 0 for count(cpu) + 1
wsgi_wsgi_file
(string) The name of the WSGI application.
wsgi