dziegler / alexandra

An abstraction layer for using Cassandra with Django

alexandra

alexandra is a thin abstraction over pycassa to interact with Cassandra from Django.

Installation

Requires Django and pycassa 0.20 or greater:

pip install -e git+http://github.com/dziegler/alexandra.git#egg=alexandra

add CASSANDRA_CLUSTER and CASSANDRA_KEYSPACE to settings.py

CASSANDRA_CLUSTER = ['localhost:9160']
CASSANDRA_KEYSPACE = 'my_keyspace'

Sample Usage

Syntax for model definition is similar to Django's, but because rows can have as many columns as you want, there's no need to define them.

import pycassa
from alexandra import cass

class EventManager(cass.Manager):

    def get_for_uuid(self, uuid):
        return self.get(uuid)

class Event(cass.ColumnFamily):
    """
    Event = {
        "89c23f26377e439a8e52fadec8f6bf19" = {
            "uuid": "804e39e29a6148039633e5a69f0c0870",
            "action": "landing:home"
            "ip_address": "127.0.0.1",
            "gender": "1",
        }
        ...
    }
    """
    objects = EventManager()

    class Meta:
        # defaults to pycassa.ConsistencyLevel.ONE
        read_consistency_level = pycassa.ConsistencyLevel.ONE
        # defaults to pycassa.ConsistencyLevel.ONE
        write_consistency_level = pycassa.ConsistencyLevel.QUORUM
        # defaults to settings.CASSANDRA_KEYSPACE
        keyspace = 'another_keyspace'
        # defaults to False. Set to True if this is a super column family
        super_cf = False


    def save(self, *args, **kwargs):
        super(Event, self).save(*args, **kwargs)
        TrackingUUID.objects.add_event(self['uuid'], self.pk)

Queries use the pycassa query api, along with whatever other methods you want to define in your manager.

import uuid

event = Event()
event['uuid'] = "804e39e29a6148039633e5a69f0c0870"
event['action'] = 'landing: home'
event['gender'] = "1"
event.pk = uuid.uuid4().hex
event.save()

# or you could do this
event = Event(uuid="804e39e29a6148039633e5a69f0c0870", action='landing: home', gender='1')
Event.objects.insert(uuid.uuid4().hex, event)