django-sequere 0.1.6

A generic application to follow a resource with multiple backends

A generic application to follow a resource with multiple backends (db, redis, etc.)

Compatibility

This library is compatible with:

• python2.6, django1.4

• python2.6, django1.5

• python2.6, django1.6

• python2.7, django1.4

• python2.7, django1.5

• python2.7, django1.6

• python3.3, django1.5

• python3.3, django1.6

If I’m a liar, you can ping me.

Installation

1. Either check out the package from GitHub or it pull from a release via PyPI

   pip install django-sequere

2. Add sequere to your INSTALLED_APPS

   INSTALLED_APPS = (
       'sequere',
   )

Usage

In Sequere any resources can follow any resources and vice versa.

Let’s say you have two models:

# models.py

from django.db import models

class User(models.Model):
    username = models.Charfield(max_length=150)


class Project(models.Model):
    name = models.Charfield(max_length=150)

Now you to register them in sequere to identify them when a resource is following another one.

# sequere_registry.py

from .models import Project, User

import sequere

sequere.register(User)
sequere.register(Project)

Sequere uses the same concepts as Django Admin, so if you have already used it, you will not be lost.

Last step is to tell Sequere to autodiscover your registered models:

# urls.py

from django.conf.urls.defaults import patterns

import sequere; sequere.autodiscover()


urlpatterns = patterns(
    '',
    # Your urls here
)

You can now use Sequere like any other application, let’s play with it:

In [1]: from sequere.models import (follow, unfollow, get_followings_count, is_following,
                                    get_followers_count, get_followers, get_followings)

In [2]: from myapp.models import User, Project

In [3]: user = User.objects.create(username='thoas')

In [4]: project = Project.objects.create(name'La classe americaine')

In [5]: follow(user, project)  # thoas will now follow "La classe americaine"

In [6]: is_following(user, project)
True

In [7]: get_followers_count(project)
1

In [8]: get_followings_count(user)
1

In [9]: get_followers(user)
[]

In [10]: get_followers(project)
[(<User: thoas>, datetime.datetime(2013, 10, 25, 4, 41, 31, 612067))]

In [11]: get_followings(user)
[(<Project: La classe americaine, datetime.datetime(2013, 10, 25, 4, 41, 31, 612067))]

If you are as lazy as me to provide the original instance in each sequere calls, use SequereMixin:

# models.py

from django.db import models

from sequere.mixin import SequereMixin

class User(SequereMixin, models.Model):
    username = models.Charfield(max_length=150)

class Project(SequereMixin, models.Model):
    name = models.Charfield(max_length=150)

Now you can use calls directly from the instance:

In [1]: from myapp.models import User, Project

In [2]: user = User.objects.create(username='thoas')

In [3]: project = Project.objects.create(name'La classe americaine')

In [4]: user.follow(project)  # thoas will now follow "La classe americaine"

In [5]: user.is_following(project)
True

In [6]: project.get_followers_count()
1

In [7]: user.get_followings_count()
1

In [8]: user.get_followers()
[]

In [9]: project.get_followers()
[(<User: thoas>, datetime.datetime(2013, 10, 25, 4, 41, 31, 612067))]

In [10]: user.get_followings()
[(<Project: La classe americaine, datetime.datetime(2013, 10, 25, 4, 41, 31, 612067))]

So much fun!

Backends

sequere.backends.database.DatabaseBackend

A database backend to store your follows in you favorite database using the Django’s ORM.

To use this backend you will have to add sequere.backends.database to your INSTALLED_APPS

INSTALLED_APPS = (
    'sequere',
    'sequere.backends.database',
)

The follower will be identified by the couple (from_identifier, from_object_id) and the following by (to_identifier, to_object_id).

Each identifiers are taken from the registry. For example, if you want to create a custom identifier key from a model you can customized it like so:

# sequere_registry.py

from myapp.models import Project

from sequere.base import ModelBase

import sequere


class ProjectSequere(ModelBase):
    identifier = 'projet' # the french way ;)

sequere.registry(Project, ProjectSequere)

sequere.backends.redis.RedisBackend

We are using exclusively Sorted Sets in this Redis implementation.

Create a uid for a new resource

INCR sequere:global:uid    =>  1
SET sequere:uid:{identifier}:{id} 1
HMSET sequere:uid::{id} identifier {identifier} object_id {id}

Store followers count

INCR sequere:uid:{to_uid}:followers:count => 1
INCR sequere:uid:{to_uid}:followers:{from_identifier}:count => 1

Store followings count

INCR sequere:uid:{from_uid}:followings:count => 1
INCR sequere:uid:{from_uid}:followings:{to_identifier}:count => 1

Add a new follower

ZADD sequere:uid:{to_uid}:followers {from_uid} {timestamp}
ZADD sequere:uid:{to_uid}:followers:{from_identifier} {from_uid} {timestamp}

Add a new following

ZADD sequere:uid:{from_uid}:followings {to_uid} {timestamp}
ZADD sequere:uid:{from_uid}:followings{to_identifier} {to_uid} {timestamp}

Retrieve the followers uids

ZRANGEBYSCORE sequere:uid:{uid}:followers -inf +inf

Retrieve the followings uids

ZRANGEBYSCORE sequere:uid:{uid}:followings =inf +inf

With this implementation you can retrieve your followers ordered

ZREVRANGEBYSCORE sequere:uid:{uid}:followers +inf -inf

sequere.backends.redis.RedisFallbackBackend

If you want to store follows in Redis and in your database with asynchronous tasks, this backend is for you.

To run asynchronous tasks, we are using Celery tasks.

To use this backend you will have to install both sequere.backends.database and sequere.backends.redis to your INSTALLED_APPS

INSTALLED_APPS = (
    'sequere',
    'sequere.backends.database',
    'sequere.backends.redis',
)

Configuration

SEQUERE_BACKEND_CLASS

The backend used to store follows

Defaults to sequere.backends.database.Databasebackend.

SEQUERE_REDIS_CONNECTION

A dictionary of parameters to pass to the to Redis client, e.g.:

SEQUERE_REDIS_CONNECTION = {
    'host': 'localhost',
    'port': 6379,
    'db': 0,
}

Alternatively you can use a URL to do the same:

SEQUERE_REDIS_CONNECTION = 'redis://username:password@localhost:6379/0'

SEQUERE_REDIS_CONNECTION_CLASS

An (optional) dotted import path to a connection to use, e.g.:

SEQUERE_REDIS_CONNECTION_CLASS = 'myproject.myapp.mockup.Connection'

SEQUERE_REDIS_PREFIX

The (optional) prefix to be used for the key when storing in the Redis database. Defaults to ‘sequere:’. E.g.:

SEQUERE_REDIS_PREFIX = 'sequere:myproject:'

Defaults to sequere:.

Resources

• haplocheirus: a Redis backed storage engine for timelines written in Scala

• Case study from Redis documentation: write a twitter clone

• Amico: relationships backed by Redis

• django-constance: a multi-backends settings management application