Django Bootstrapping with Ease

Bootstrapping
Django with ease
OSCON 2012
www.concentricsky.com
@concentricsky // biglan / wiggins / bothun

Thursday, July 19, 12

Introductions

Mike Biglan Wiggins Josh Bothun
CTO Architect Senior Developer

@coﬃndragger


Areas of Concentric Sky

Web/Django Mobile Enterprise


(Some) Technologies We Use

• Chef • Backbone.js
• Jenkins • Jinja2
• AWS • Celery
• Sphinx • DebugToolbar
• Memcached • jQuery / jQueryUI
• South • Compass / Sass
• git • Mongo & MySQL


Released CSky Creations

• djenesis – Easy Django Bootstrapping
• breakdown - Lightweight jinja2 template
prototyping server

• django-cachemodel – Automatic caching
for django models


CSky Creations in the Works

• skycloud – Tool for AWS auto-scaling
• django-skycms – CMS as a library
• django-sky-visitor – Invitations, email
conﬁrmation, etc

• django-client-admin – Flexible admin for
client


CSky Teams

10 Django Team

STAFF

50+
5 Design Team

9 PM Team

3 System Admins


Team Interfacing

• Each project is a mix from each team
• Members might switch amongst projects
• Interfaces between teams
• Clean separation of handoﬀs and
responsibilities

• Best-practices shared within teams


“Bootstrapping”

• Pulling one up by one’s bootstraps
• Computers do this much better than humans
• Django – starting a project, new or existing


Bootstrapping with Ease

Making booting (and rebooting) a
django project as easy as possible

• Ease is a continually moving target
• Shouldn’t sacriﬁce other goals for ease (e.g.
security, modularity, be PHP)


Moving Targets

Moving targets create new
problems. And new solutions.

• CGI – Solving static HTML
• JavaScript – Solving non-interactivity
• CSS – Solving 100+ HTML pages
• Puppet/Chef – Solving 100+ servers


Problem/Solution Lifecycle

1. Problem grows

2. Many create their own solution; some
polish; some release

3. Community ﬂocks to one (or a few) solutions

4. Solution(s) gets anointed and others die oﬀ


Goals of Easy Bootstrapping

1. More people using Django
2. More people using Django better


More People Using Django

• As few commands as possible to try
Django out

• And to try someone else’s project out.
• Must be highly likely to just work
• All especially critical for beginners
• Django’s runserver & sqlite...great!
• It just works...

Making Mistakes should be Hard

• Checklists are great
• The best checklists
are invisible

• To automate lists of
commands, must
have consistency


Consistency Makes things Easier

• Ease of replication across servers
• Ease of sharing
• Both templates and existing projects
• Easier to build upon


Consistently Standardized

• Standardization: a tool to get to
consistency

• This can be in an organization. Or the full
community

• Oh yeah, and...


Standard had Better be Right


Fragmentation

• Poor standards lead to fragmentation
• Hard to build things on top of
fragmented environments

• Imagine building for single browser. Not
Mosaic.


Android Fragmentation

http://www.businessinsider.com/android-fragmentation-chart-from-opensignalmaps-2012-5


Flexibility vs Standardization

• Standardization can be rigid; can kill ﬂexibility
• Especially as the target moves
• E.g. contrib.auth
• Flexibility allows preference, innovation
• Best of both worlds is standardization with
structured options of ﬂexibility

• Django does this well

Django

• Django is a set of higher-order building blocks
• If blocks are too large, sacrifices what can be
made (i.e. not flexibile)

• If blocks are too small, becomes inefficient
and unmanageable

• If block types are wrong, not loosely
coupled (i.e. non-orthogonal)


3 Stages of Project
Structure Grief
• Denial
• Bargaining
• Acceptance


Denial

I’ll just take the
easy way out...

• Stuﬀ required libraries in a ‘lib’ directory
• Stick django there too
• Name everything MyProjectSomething


Denial

I’ll just take the easy way out...

Why this doesn’t work
• project starts to get bloated
• version management becomes a headache
• upgrade paths become tangled


Bargaining

We’ll just adopt some
standard practices...
1. Have the team argue about which way to do things

2. Assign someone to write a document about it

3. ???

4. Ignore it when you start a new project


Bargaining

We’ll just adopt some standard practices...

Why this doesn’t work
• Projects become inconsistent
• It is not in source control
• No way to manage changes across projects
• There is no history of changes or discussion


Acceptance

Embrace the community
• requirements.txt, version management
• also solves the ‘git submodule’ problem
• virtualenv is great, always use it


Acceptance

No, really, use virtualenv
• dependency management
• concurrent project management
• sand-boxing
• solves the “chicken-n-egg” problem
• replication

What’s in a template?

• For a django project, there are two styles:

1. toplevel directory is python code

2. toplevel directory is a website project


Toplevel is python code

./manage.py
./my_project/__init__.py
• Pros
./my_project/settings.py
./my_project/urls.py
• More pythonic; Everything
./my_project/wsgi.py
is python code

Django’s default template • It just works
• Cons
• Everything is python code
• Where do non public ﬁles
go?


Default Django Project
./manage.py
• Where do apps go?
./my_project/wsgi.py • How about ./my_project/
./my_project/my_app/__init__.py my_app/?
./my_project/my_app/models.py

• Name then becomes
‘my_project.my_app’

• What about reusability?
• What if I want to rename
my_project?


./manage.py
• Where do apps go?
./my_project/wsgi.py • How about ./my_app/?
• Better for reusability, but...
./my_app/__init__.py
./my_app/models.py

• Now I have to add ./ to the
PYTHON_PATH


./manage.py
./myapp1/models.py
./myapp1/urls.py
• What was the name
./myapp2/models.py again?
• Was it ‘myapp1’ or ‘myapp2’
./myapp2/urls.py
./myapp3/models.py
./myapp3/urls.py that contains the main urls
and settings...


Toplevel is website project

• Pros
./manage.py
./wsgi.py
./requirements.txt

• Closer to real world
./apps/mainsite/__init__.py
./apps/mainsite/settings.py
./apps/mainsite/settings_local.py
./apps/mainsite/urls.py environments
./apps/my_app/models.py

• Consistency across
./apps/my_app/urls.py

projects

• Cons
• ??? None I guess!
http://github.com/concentricsky/djenesis-template.git


./manage.py
./wsgi.py
./requirements.txt
./apps/mainsite/settings_local.py.example
./apps/mainsite/urls.py

Python code is sandboxed
• only have to add ./apps to PYTHON_PATH
• everything else is ignored by WSGI server


./manage.py
./wsgi.py
./requirements.txt

Consistent Entry Point Name
• I always know where to look ﬁrst: ./apps/
mainsite/urls.py

• More important than it may seem at ﬁrst blush

./manage.py
./wsgi.py
./requirements.txt

settings_local
• Loaded after settings.py as overrides.

• Easily set up a local development environment.

• Production credentials are at no risk.

• Easily deploy devel, staging, production stacks.


./manage.py
./wsgi.py
./requirements.txt

I have requirements.txt
• Library dependencies and versioning is simple.
• New developers can start working quicker.
• Simple virtualenv integration

Okay, but now what?

1. Install and use virtualenv

2. Design and use a template


How hard can it be?


Taking a closer look

$ mkvirtualenv myproject && workon myproject
OR
$ virtualenv ~/myproject/env && source ~/myproject/env/
bin/activate

THEN
$ git clone http://github.com/my/template.git /tmp/
mytemplate

$ pip install django>=1.4

$ django-admin.py startproject --template=/tmp/
mytemplate ~/myproject/code

$ rm -rf /tmp/mytemplate


Our approach

Djenesis: our solution to the
bootstrapping problem


djenesis

• What is it?
• A tool that facilitates the process of
creating new and setting up existing Django
projects.

• Available on github & PyPi (apache license)
• github.com/concentricsky/djenesis


djenesis - Benefits

• Simplifies routine workflows for:

• Starting a new project

• Getting an existing project up and running with ease

• Encourages developers to use a standard project
structure and best python practices (virtualenv)

• Allows external project templates

• Supports git, svn, hg URLs

• Supports Django 1.4 project templates


djenesis - History

1. Single zip ﬁle of a stub project

2. Script that wrapped stub

3. Decouples templates from script

4. Can use external templates, git URL

5. Now: supports Django 1.4 templates


djenesis - External Templates

• Inﬂating a project from a git/svn/hg source
means you can (and should) version
control your project templates

• Collaborate with your internal teams on an
ideal project structure


djenesis Stack


djenesis - Setup

• Requires virtualenv
• Install virtualenv through pip or easy_install
• Install djenesis through pip or easy_install


djenesis – New Project

Before
$ virtualenv ~/myproject/env
$ source ~/myproject/env/bin/activate
$ pip install django
$ git clone github.com/my/template.git /tmp/tmpl
$ django-admin.py startproject --template=/tmp/tmpl ~/
myproject/code
$ rm -rf /tmp/tmpl

With djenesis
$ djenesis myproject git+https://github.com/my/template.git


djenesis – Existing Project

Before
$ virtualenv ~/myproject/env
$ git clone github.com/my/project.git ~/myproject/code
$ pip install -r ~/myproject/code/requirements.txt

With djenesis
$ djenesis myproject -i git+https://github.com/my/project.git


djenesis - Conﬁguration

• Use a default template
DJENESIS_DEFAULT_TEMPLATE=/path/to/template

• Always use virtualenvwrapper (if installed)
DJENESIS_VIRTUALENVWRAPPER=1

• Set these in your .bashrc


djenesis – Next?

1. startapp template in project template

2. setup.py Support

3. djenesis post-create hooks for common tasks
(copy local settings, syncdb, import ﬁxtures)

4. Activate virtualenv when djenesis is called


Django Bootstrapping with Ease

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