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import logging, os
from typing import Optional, Union
from .backend._Backend import _Backend
from .backend.BackendEnum import BackendEnum
from .backend.inmemory.InMemoryBackend import InMemoryBackend
from .backend.redis.RedisBackend import RedisBackend
LOGGER = logging.getLogger(__name__)
BACKENDS = {
BackendEnum.INMEMORY.value: InMemoryBackend,
BackendEnum.REDIS.value: RedisBackend,
#BackendEnum.MONGODB.value: MongoDBBackend,
#BackendEnum.RETHINKDB.value: RethinkDBBackend,
#BackendEnum.ETCD.value: EtcdBackend,
}
DEFAULT_DB_BACKEND = BackendEnum.INMEMORY
def get_database_backend(backend : Optional[Union[str, BackendEnum]] = None, **settings) -> _Backend:
# return an instance of Database initialized with selected backend.
# The backend is selected using following criteria (first that is not None is selected):
# 1. user selected by parameter (backend=...)
# 2. environment variable DB_BACKEND
# 3. default backend: INMEMORY
if backend is None: backend = os.environ.get('DB_BACKEND', DEFAULT_DB_BACKEND)
if backend is None: raise Exception('Database Backend not specified')
if isinstance(backend, BackendEnum): backend = backend.value
backend_class = BACKENDS.get(backend)
if backend_class is None: raise Exception('Unsupported DatabaseBackend({})'.format(backend))
LOGGER.info('Selected Database Backend: {}'.format(backend))
return backend_class(**settings)