Support specifying the Redis Database to use on the host

Database zero is the default that the Python redis client uses,
so default to that to avoid breakage. Since DLQ uses KEYS it's
potentially useful to be able to run it in its own database as
that may limit the performance concerns around the KEYS command.

Author: PeterJCLaw

django_lightweight_queue/app_settings.py

@@ -43,6 +43,7 @@ def setting(suffix: str, default: T) -> T:
 REDIS_HOST = setting('REDIS_HOST', '127.0.0.1')  # type: str
 REDIS_PORT = setting('REDIS_PORT', 6379)  # type: int
 REDIS_PASSWORD = setting('REDIS_PASSWORD', None)  # type: Optional[str]
+REDIS_DATABASE = setting('REDIS_DATABASE', 0)  # type: int
 REDIS_PREFIX = setting('REDIS_PREFIX', '')  # type: str
 
 ENABLE_PROMETHEUS = setting('ENABLE_PROMETHEUS', False)  # type: bool

django_lightweight_queue/backends/redis.py

@@ -20,6 +20,7 @@ def __init__(self) -> None:
             host=app_settings.REDIS_HOST,
             port=app_settings.REDIS_PORT,
             password=app_settings.REDIS_PASSWORD,
+            db=app_settings.REDIS_DATABASE,
         )
 
     def enqueue(self, job: Job, queue: QueueName) -> None:

django_lightweight_queue/backends/reliable_redis.py

@@ -46,6 +46,7 @@ def __init__(self) -> None:
             host=app_settings.REDIS_HOST,
             port=app_settings.REDIS_PORT,
             password=app_settings.REDIS_PASSWORD,
+            db=app_settings.REDIS_DATABASE,
         )
 
     def startup(self, queue: QueueName) -> None: