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240 lines
7.8 KiB
ReStructuredText
240 lines
7.8 KiB
ReStructuredText
django-ddp
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==========
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Django_/PostgreSQL_ implementation of the Meteor DDP service, allowing Meteor_ to subscribe to changes on Django_ models. Released under the MIT license.
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Requirements
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------------
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The core concept is that events are dispatched asynchronously to browsers using WebSockets_ and server-side using a PostgreSQL_ extension to the SQL syntax called NOTIFY (and its bretheren, LISTEN and UNLISTEN). 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 Reddis or crossbar.io as they are simply not needed given the asynchronous support provided by PostgreSQL_ with psycopg2_. As an added bonus, events dispatched using NOTIFY in a transaction are only emitted if the transaction is successfully committed.
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Scalability
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-----------
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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.
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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.
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Limitations
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-----------
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* No support for the SockJS protocol to support browsers that
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don't have WebSockets_ (see http://caniuse.com/websockets for
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supported browsers).
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* Changes must be made via the Django ORM as django-ddp uses `Django
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signals`_ to receive model save/update signals.
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Installation
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------------
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Install the latest release from pypi (recommended):
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.. code:: sh
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pip install django-ddp
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Clone and use development version direct from GitHub (to test pre-release code):
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.. code:: sh
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pip install -e git+https://github.com/commoncode/django-ddp@develop#egg=django-ddp
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Example usage
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-------------
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Add 'dddp' to your settings.INSTALLED_APPS:
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.. code:: python
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# settings.py
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...
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INSTALLED_APPS = list(INSTALLED_APPS) + ['dddp']
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If you'd like support for the Meteor Accounts package (ie: login/logout
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with django.contrib.auth) consult the section on authentication below
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and use the following line instead:
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.. code:: python
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# settings.py
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...
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INSTALLED_APPS = list(INSTALLED_APPS) + ['dddp', 'dddp.accounts']
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Add ddp.py to your Django application:
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.. code:: python
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# bookstore/ddp.py
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from dddp.api import API, Collection, Publication
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from bookstore import models
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class Book(Collection):
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model = models.Book
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class Author(Collection):
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model = models.Author
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class AllBooks(Publication):
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queries = [
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models.Author.objects.all(),
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models.Book.objects.all(),
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]
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class BooksByAuthorEmail(Publication):
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def get_queries(self, author_email):
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return [
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models.Author.objects.filter(
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email=author_email,
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),
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models.Book.objects.filter(
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author__email=author_email,
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),
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]
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API.register(
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[Book, Author, AllBooks, BooksByAuthorEmail]
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)
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Start the Django DDP service:
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.. code:: sh
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DJANGO_SETTINGS_MODULE=myproject.settings dddp
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Using django-ddp as a secondary DDP connection (RAPID DEVELOPMENT)
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------------------------------------------------------------------
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Running in this manner allows rapid development through use of the hot
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code push features provided by Meteor.
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Connect your Meteor application to the Django DDP service:
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.. code:: javascript
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// bookstore.js
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if (Meteor.isClient) {
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// Connect to Django DDP service
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Django = DDP.connect('http://'+window.location.hostname+':8000/');
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// Create local collections for Django models received via DDP
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Authors = new Mongo.Collection("bookstore.author", {connection: Django});
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Books = new Mongo.Collection("bookstore.book", {connection: Django});
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// Subscribe to all books by Janet Evanovich
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Django.subscribe('BooksByAuthorEmail', 'janet@evanovich.com');
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}
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Start Meteor (from within your meteor application directory):
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.. code:: sh
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meteor
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Using django-ddp as the primary DDP connection (RECOMMENDED)
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------------------------------------------------------------
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If you'd prefer to not have two DDP connections (one to Meteor and one
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to django-ddp) you can set the `DDP_DEFAULT_CONNECTION_URL` environment
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variable to use the specified URL as the primary DDP connection in
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Meteor. When doing this, you won't need to use `DDP.connect(...)` or
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specify `{connection: Django}` on your collections. Running with
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django-ddp as the primary connection is recommended, and indeed required
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if you wish to use `dddp.accounts` to provide authentication using
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`django.contrib.auth` to your meteor app.
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.. code:: sh
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DDP_DEFAULT_CONNECTION_URL=http://localhost:8000/ meteor
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Serving your Meteor applications from django-ddp
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------------------------------------------------
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First, you will need to build your meteor app into a directory (examples
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below assume target directory named `myapp`):
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.. code:: sh
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meteor build ../myapp
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Then, add a MeteorView to your urls.py:
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.. code:: python
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from dddp.views import MeteorView
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urlpatterns = patterns(
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url('^(?P<path>/.*)$', MeteorView.as_view(
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json_path=os.path.join(
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settings.PROJ_ROOT, 'myapp', 'bundle', 'star.json',
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),
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),
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)
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Adding API endpoints (server method definitions)
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------------------------------------------------
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API endpoints can be added by calling `register` method of the
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dddp.api.API object from the ddp.py module of your Django app, on a
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subclass of dddp.api.APIMixin - both dddp.api.Collection and
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dddp.api.Publication are suitable, or you may define your own subclass
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of dddp.api.APIMixin. A good example of this can be seen in
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dddp/accounts/ddp.py in the source of django-ddp.
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Authentication
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--------------
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Authentication is provided using the standard meteor accounts system,
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along with the `accounts-secure` package which turns off Meteor's
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password hashing in favour of using TLS (HTTPS + WebSockets). This
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ensures strong protection for all data over the wire. Correctly using
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TLS/SSL also protects your site against man-in-the-middle and replay
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attacks - Meteor is vulnerable to both of these without using
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encryption.
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Add `dddp.accounts` to your `settings.INSTALLED_APPS` as described in
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the example usage section above, then add `tysonclugg:accounts-secure`
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to your Meteor application (from within your meteor application
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directory):
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.. code:: sh
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meteor add tysonclugg:accounts-secure
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Then follow the normal procedure to add login/logout views to your
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Meteor application.
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Contributors
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------------
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`Tyson Clugg <https://github.com/tysonclugg>`_
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* Author, conceptual design.
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`Yan Le <https://github.com/janusle>`_
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* Validate and bug fix dddp.accounts submodule.
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`MEERQAT <http://meerqat.com.au/>`_
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* Project sponsor - many thanks for allowing this to be released under an open source license!
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`David Burles <https://github.com/dburles>`_
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* Expert guidance on how DDP works in Meteor.
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`Brenton Cleeland <https://github.com/sesh>`_
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* Great conversations around how collections and publications can limit visibility of published documents to specific users.
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`Muhammed Thanish <https://github.com/mnmtanish>`_
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* Making the `DDP Test Suite <https://github.com/meteorhacks/ddptest>`_ available.
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.. _Django: https://www.djangoproject.com/
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.. _Django signals: https://docs.djangoproject.com/en/stable/topics/signals/
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.. _PostgreSQL: http://postgresql.org/
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.. _psycopg2: http://initd.org/psycopg/
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.. _WebSockets: http://www.w3.org/TR/websockets/
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.. _Meteor: http://meteor.com/
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