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Description:

djangoddp 0.19.1

Django DDP is a Django/PostgreSQL implementation of the Meteor DDP
server, allowing Meteor to subscribe to changes on Django models.
Released under the MIT license.

Requirements
You must be using PostgreSQL with psycopg2 in your Django project
for django-ddp to work. There is no requirement on any asynchronous
framework such as Redis or crossbar.io as they are simply not needed
given the asynchronous support provided by PostgreSQL with psycopg2.
Since the test suite includes an example Meteor project, running that
requires that Meteor is installed (and meteor is in your PATH).

Installation
Install the latest release from pypi (recommended):
pip install django-ddp
Clone and use development version direct from GitHub to test pre-release
code (no GitHub account required):
pip install -e git+https://github.com/commoncode/django-ddp@develop#egg=django-ddp

Overview and getting started

Django DDP registers handlers for Django signals on all model save/update operations.

Add 'dddp' to INSTALLED_APPS in your project settings file.

Each Django application (ie: your code) registers Collections and Publications via ddp sub-modules for all INSTALLED_APPS.

Register collections and publications in a file named dddp.py inside your application module.

Clients subscribe to publications, entries are written into the dddp.Subscription and dddp.SubscriptionCollection model tables and the get_queries method of publications are called to retrieve the Django ORM queries that contain the objects that will be sent to the client.

Run manage.py migrate to update your database so it has the necessary tables needed for tracking client subscriptions.

When models are saved, the Django DDP signal handlers send change messages to clients subscribed to relevant publications.

Use the model save() and delete() methods as appropriate in your application code so that appropriate signals are raised and change messages are sent.

Gevent is used to run WebSocket connections concurrently along with any Django views defined in your project (via your project urls.py).

Run your application using the dddp command which sets up the gevent mainloop and serves your Django project views. This command takes care of routing WebSocket connections according to the URLs that Meteor uses, do not add URLs for WebSocket views to your project urls.py.

Scalability
All database queries to support DDP events are done once by the server
instance that has made changes via the Django ORM. Django DDP multiplexes
messages for active subscriptions, broadcasting an aggregated change
message on channels specific to each Django model that has been published.
Peer servers subscribe to aggregate broadcast events which are
de-multiplexed and dispatched to individual client connections.
No additional database queries are required for de-multiplexing
or dispatch by peer servers.

Limitations

No support for the SockJS XHR fallback protocol to support browsers
that don’t have WebSockets (see http://caniuse.com/websockets for
supported browsers). It is noteworthy that the only current browser
listed that doesn’t support WebSockets is Opera Mini, which doesn’t
support pages that use EcmaScript (JavaScript) for interactivity
anyway. Offering SockJS XHR fallback wouldn’t help to substantially
increase browser support: if Opera Mini is excluded then all current
browser versions including IE, Edge, Firefox, Chrome, Safari, Opera,
iOS Safari, Android Browser Android and Chrome for Android are
supported. Having said all that, pull requests are welcome.
Changes must be made via the Django ORM as django-ddp uses Django
signals to receive model save/update signals. There are no
technical reasons why database triggers couldn’t be used - pull
requests are welcome.

Example usage
Add ‘dddp’ to your settings.INSTALLED_APPS:
# settings.py
...
INSTALLED_APPS = list(INSTALLED_APPS) + ['dddp']
If you’d like support for the Meteor Accounts package (ie: login/logout
with django.contrib.auth) consult the section on authentication below
and use the following line instead:
# settings.py
...
INSTALLED_APPS = list(INSTALLED_APPS) + ['dddp', 'dddp.accounts']
Add ddp.py to your Django application:
# bookstore/ddp.py

from dddp.api import API, Collection, Publication
from bookstore import models

class Book(Collection):
model = models.Book

class Author(Collection):
model = models.Author

class AllBooks(Publication):
queries = [
models.Author.objects.all(),
models.Book.objects.all(),
]

class BooksByAuthorEmail(Publication):
def get_queries(self, author_email):
return [
models.Author.objects.filter(
email=author_email,
),
models.Book.objects.filter(
author__email=author_email,
),
]

API.register(
[Book, Author, AllBooks, BooksByAuthorEmail]
)
Start the Django DDP service:
DJANGO_SETTINGS_MODULE=myproject.settings dddp

Using django-ddp as a secondary DDP connection (RAPID DEVELOPMENT)
Running in this manner allows rapid development through use of the hot
code push features provided by Meteor.
Connect your Meteor application to the Django DDP service:
// bookstore.js
if (Meteor.isClient) {
// Connect to Django DDP service
Django = DDP.connect('http://'+window.location.hostname+':8000/');
// Create local collections for Django models received via DDP
Authors = new Mongo.Collection("bookstore.author", {connection: Django});
Books = new Mongo.Collection("bookstore.book", {connection: Django});
// Subscribe to all books by Janet Evanovich
Django.subscribe('BooksByAuthorEmail', 'janet@evanovich.com');
}
Start Meteor (from within your meteor application directory):
meteor

Using django-ddp as the primary DDP connection (RECOMMENDED)
If you’d prefer to not have two DDP connections (one to Meteor and one
to django-ddp) you can set the DDP_DEFAULT_CONNECTION_URL environment
variable to use the specified URL as the primary DDP connection in
Meteor. When doing this, you won’t need to use DDP.connect(…) or
specify {connection: Django} on your collections. Running with
django-ddp as the primary connection is recommended, and indeed required
if you wish to use dddp.accounts to provide authentication using
django.contrib.auth to your meteor app.
DDP_DEFAULT_CONNECTION_URL=http://localhost:8000/ meteor

Serving your Meteor applications from django-ddp
First, you will need to build your meteor app into a directory (examples
below assume target directory named myapp):
meteor build ../myapp
Then, add a MeteorView to your urls.py:
from dddp.views import MeteorView

urlpatterns = patterns(
url('^(?P<path>/.*)$', MeteorView.as_view(
json_path=os.path.join(
settings.PROJ_ROOT, 'myapp', 'bundle', 'star.json',
),
),
)

Adding API endpoints (server method definitions)
API endpoints can be added by calling register method of the
dddp.api.API object from the ddp.py module of your Django app, on a
subclass of dddp.api.APIMixin - both dddp.api.Collection and
dddp.api.Publication are suitable, or you may define your own subclass
of dddp.api.APIMixin. A good example of this can be seen in
dddp/accounts/ddp.py in the source of django-ddp.

Authentication
Authentication is provided using the standard meteor accounts system,
along with the accounts-secure package which turns off Meteor’s
password hashing in favour of using TLS (HTTPS + WebSockets). This
ensures strong protection for all data over the wire. Correctly using
TLS/SSL also protects your site against man-in-the-middle and replay
attacks - Meteor is vulnerable to both of these without using
encryption.
Add dddp.accounts to your settings.INSTALLED_APPS as described in
the example usage section above, then add tysonclugg:accounts-secure
to your Meteor application (from within your meteor application
directory):
meteor add tysonclugg:accounts-secure
Then follow the normal procedure to add login/logout views to your
Meteor application.

Contributors

Tyson Clugg

Author, conceptual design.

Yan Le

Validate and bug fix dddp.accounts submodule.

MEERQAT

Project sponsor - many thanks for allowing this to be released under an open source license!

David Burles

Expert guidance on how DDP works in Meteor.

Brenton Cleeland

Great conversations around how collections and publications can limit visibility of published documents to specific users.

Muhammed Thanish

Making the DDP Test Suite available.

This project is forever grateful for the love, support and respect given
by the awesome team at Common Code.