Temporary hack. Support for Redis Sentinel as result backend for Celery 4.0.2

celery_sentinel.py

"""
This module adds Redis Sentinel backend support to Celery.
Current version (4.0.2) of Celery supports Redis sentinel only as broker but
not as result backend.

To use it in Django::
    import register_celery_alias
    register_celery_alias('redis-sentinel')
    app = Celery('my_app')
    app.config_from_object('django.conf:settings', namespace='CELERY')

Example config::
    CELERY_RESULT_BACKEND = 'redis-sentinel://...'
    CELERY_REDIS_SENTINEL_SENTINELS =  [('sentinel-host01', '26379'),
                                        ('sentinel-host02', '26379'),
                                        ('sentinel-host03', '26379'),
                                       ]
    CELERY_REDIS_SENTINEL_SERVICE_NAME = 'mymaster'
    CELERY_REDIS_SENTINEL_DB = 2

Stripped down version of https://gist.github.com/reclosedev/8460004
"""
from celery.app.backends import BACKEND_ALIASES
from celery.backends.redis import RedisBackend
from kombu.utils import cached_property
from redis import StrictRedis
from redis.sentinel import Sentinel


class RedisSentinelBackend(RedisBackend):

    def __init__(self, sentinels=None, sentinel_timeout=None,
                 socket_timeout=None, service_name=None, min_other_sentinels=0,
                 sentinel_db=0, **kwargs):
        super(RedisSentinelBackend, self).__init__(**kwargs)
        conf = self.app.conf

        def _get(key):
            try:
                return conf['CELERY_REDIS_SENTINEL_%s' % key]
            except KeyError:
                pass

        self.sentinels = sentinels or _get('SENTINELS')
        self.sentinel_timeout = sentinel_timeout or _get('SENTINEL_TIMEOUT')
        self.socket_timeout = socket_timeout or _get('SOCKET_TIMEOUT')
        self.service_name = service_name or _get('SERVICE_NAME')
        self.min_other_sentinels = min_other_sentinels
        if self.min_other_sentinels == 0 and _get('MIN_OTHER_SENTINELS') != 0:
            self.min_other_sentinels = _get('MIN_OTHER_SENTINELS')
        self.sentinel_db = sentinel_db
        if self.sentinel_db == 0 and _get('DB') != 0:
            self.sentinel_db = _get('DB')

    @cached_property
    def client(self):
        sentinel = Sentinel(
            self.sentinels,
            min_other_sentinels=self.min_other_sentinels,
            password=self.password,
            sentinel_kwargs={
                'socket_timeout': self.sentinel_timeout,
            }
        )
        return sentinel.master_for(
            self.service_name,
            redis_class=StrictRedis,
            db=self.sentinel_db,
            socket_timeout=self.socket_timeout
        )


def register_celery_alias(alias='redis-sentinel'):
    BACKEND_ALIASES[alias] = 'utils.celery_sentinel.RedisSentinelBackend'