add support for redis sentinel on django-redis

redis_sentinel.py

# -*- coding: utf-8 -*-

import logging

from django.conf import settings
from django.core.exceptions import ImproperlyConfigured

from redis.sentinel import Sentinel

from django_redis.client import DefaultClient

DJANGO_REDIS_LOGGER = getattr(settings, "DJANGO_REDIS_LOGGER", False)
DJANGO_REDIS_CLOSE_CONNECTION = getattr(settings,
                                        "DJANGO_REDIS_CLOSE_CONNECTION", False)


class SentinelClient(DefaultClient):
    """
    Sentinel client object extending django-redis DefaultClient
    """

    def __init__(self, server, params, backend):
        """
        Slightly different logic than connection to multiple Redis servers.
        Reserve only one write and read descriptors, as they will be closed on exit anyway.
        """
        super(SentinelClient, self).__init__(server, params, backend)
        self._client = None
        self._connection_string = server
        self.log = logging.getLogger((DJANGO_REDIS_LOGGER or __name__))

    def parse_connection_string(self, constring):
        """
        Parse connection string in format:
            master_name/sentinel_server:port,sentinel_server:port/db_id
        Returns master name, list of tuples with pair (host, port) and db_id
        """
        try:
            connection_params = constring.split('://')
            if len(connection_params) > 1:
                connection_params = connection_params[1].split('/')
            master_name = connection_params[0]
            servers = [
                host_port.split(':')
                for host_port in connection_params[1].split(',')
            ]
            sentinel_hosts = [(host, int(port)) for host, port in servers]
            db = connection_params[2]
        except (ValueError, TypeError, IndexError):
            raise ImproperlyConfigured("Incorrect format '%s'" % (constring))

        return master_name, sentinel_hosts, db

    def get_client(self, write=True, tried=(), show_index=False):
        """
        Method used to obtain a raw redis client.

        This function is used by almost all cache backend
        operations to obtain a native redis client/connection
        instance.
        """
        if self._client is None:
            self._client = self.connect()

        if show_index:
            return self._client, 0
        else:
            return self._client

    def connect(self, index=0):
        """
        Creates a redis connection with connection pool.
        """
        master_name, sentinel_hosts, db = self.parse_connection_string(
            self._connection_string)

        sentinel_timeout = self._options.get('SENTINEL_TIMEOUT', 1)
        password = self._options.get('PASSWORD', None)
        sentinel = Sentinel(
            sentinel_hosts, socket_timeout=sentinel_timeout, password=password)

        return sentinel.master_for(
            master_name,
            socket_timeout=sentinel_timeout,
            db=db,
        )

    def close(self, **kwargs):
        """
        Closing old connections, as master may change in time of inactivity.
        """
        if DJANGO_REDIS_CLOSE_CONNECTION and self._client is not None:
            del self._client