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from contextlib import contextmanager
import typing as t
from redis import Redis
from .local import LocalStack, release_local
class NoRedisConnectionException(Exception):
pass
@contextmanager
def Connection(connection: t.Optional['Redis'] = None): # noqa
if connection is None:
connection = Redis()
push_connection(connection)
try:
yield
finally:
popped = pop_connection()
assert popped == connection, \
'Unexpected Redis connection was popped off the stack. ' \
'Check your Redis connection setup.'
def push_connection(redis: 'Redis'):
"""
Pushes the given connection on the stack.
Args:
redis (Redis): A Redis connection
"""
_connection_stack.push(redis)
def pop_connection():
"""
Pops the topmost connection from the stack.
"""
return _connection_stack.pop()
def use_connection(redis: t.Optional['Redis'] = None):
"""
Clears the stack and uses the given connection. Protects against mixed
use of use_connection() and stacked connection contexts.
Args:
redis (t.Optional[Redis], optional): A Redis Connection. Defaults to None.
"""
assert len(_connection_stack) <= 1, \
'You should not mix Connection contexts with use_connection()'
release_local(_connection_stack)
if redis is None:
redis = Redis()
push_connection(redis)
def get_current_connection():
"""
Returns the current Redis connection (i.e. the topmost on the
connection stack).
"""
return _connection_stack.top
def resolve_connection(connection: t.Optional['Redis'] = None) -> 'Redis':
"""
Convenience function to resolve the given or the current connection.
Raises an exception if it cannot resolve a connection now.
Args:
connection (t.Optional[Redis], optional): A Redis connection. Defaults to None.
Raises:
NoRedisConnectionException: If connection couldn't be resolved.
Returns:
Redis: A Redis Connection
"""
if connection is not None:
return connection
connection = get_current_connection()
if connection is None:
raise NoRedisConnectionException('Could not resolve a Redis connection')
return connection
_connection_stack = LocalStack()
__all__ = ['Connection', 'get_current_connection', 'push_connection',
'pop_connection', 'use_connection']
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