Full Stack Django on Google App Engine(abbreviated)

at Austin PUG February 10, 2010

Percy Wegmann presenting

The Problem

You want to run a recent version of Django on Google App Engine.

Solution 1 – Django app-engine-patch

http://code.google.com/p/app-engine-patch/

Supports authentication frameworkSupports session management and caching backendSupports admin interfaceSupports Django formsSupports a bunch of other things as wellCan be slow because it is almost a complete drop-in replacement for Django (and all of those modules need to get loaded by App Engine)

Solution 2 – Built-in Django 1.1 with App Engine Helper

http://code.google.com/appengine/docs/python/tools/libraries.htmlhttp://code.google.com/p/google-app-engine-django/

Supports authentication frameworkSupports session management and caching backendDoes not support admin interface (App Engine has its own admin)Does not support Django forms (App Engine has its own forms)Faster than app-engine-patch because Django 1.1 is supported by App Engine as a preloaded built-in

How it Works - main.py

import os(os.environ)['DJANGO_SETTINGS_MODULE'] = 'settings'

# Standard Python imports.import sys

from appengine_django import InstallAppengineHelperForDjangoInstallAppengineHelperForDjango("1.1")

from appengine_django import have_django_zipfrom appengine_django import django_zip_path

# Google App Engine imports.from google.appengine.ext.webapp import util

# Import the part of Django that we use here.import django.core.handlers.wsgi

def main(): # Ensure the Django zipfile is in the path if required. if have_django_zip and django_zip_path not in sys.path: sys.path.insert(1, django_zip_path)

# Create a Django application for WSGI. application = django.core.handlers.wsgi.WSGIHandler()

# Run the WSGI CGI handler with that application. util.run_wsgi_app(application)

if __name__ == '__main__': main()

How it Works – static media handling

I put my static media in the folder static in my project root

Then I define static_dir entries in app.yaml

- url: /static/4 static_dir: static/

- url: /static static_dir: static/

- url: /.* script: main.py

And in settings.py I define a MEDIA_ROOT setting that points at this path

MEDIA_URL = “/static/4”

for external permalinks

versioned to allow media changes

dynamic Django urls

How it Works – app.yaml

application: bidtective2version: 1runtime: pythonapi_version: 1

default_expiration: '7d'

handlers:- url: /remote_api script: $PYTHON_LIB/google/appengine/ext/remote_api/handler.py secure: optional login: admin

# The below handler is required by bigtable search- url: /bts/.* script: bts/main.py secure: optional login: admin

- url: /admin/.* script: main.py secure: optional login: admin - url: /task/.* script: main.py secure: optional login: admin - url: /static/4 static_dir: static/

- url: /static static_dir: static/

- url: /.* script: main.py