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"""
Working with Backends.
"""
import sys
from carrot.utils import rpartition
DEFAULT_BACKEND = "carrot.backends.pyamqplib.Backend"
BACKEND_ALIASES = {
"amqp": "carrot.backends.pyamqplib.Backend",
"amqplib": "carrot.backends.pyamqplib.Backend",
"stomp": "carrot.backends.pystomp.Backend",
"stompy": "carrot.backends.pystomp.Backend",
"memory": "carrot.backends.queue.Backend",
"mem": "carrot.backends.queue.Backend",
"pika": "carrot.backends.pikachu.AsyncoreBackend",
"pikachu": "carrot.backends.pikachu.AsyncoreBackend",
"syncpika": "carrot.backends.pikachu.SyncBackend",
}
_backend_cache = {}
def resolve_backend(backend=None):
backend = BACKEND_ALIASES.get(backend, backend)
backend_module_name, _, backend_cls_name = rpartition(backend, ".")
return backend_module_name, backend_cls_name
def _get_backend_cls(backend=None):
backend_module_name, backend_cls_name = resolve_backend(backend)
__import__(backend_module_name)
backend_module = sys.modules[backend_module_name]
return getattr(backend_module, backend_cls_name)
def get_backend_cls(backend=None):
"""Get backend class by name.
The backend string is the full path to a backend class, e.g.::
"carrot.backends.pyamqplib.Backend"
If the name does not include "``.``" (is not fully qualified),
the alias table will be consulted.
"""
backend = backend or DEFAULT_BACKEND
if backend not in _backend_cache:
_backend_cache[backend] = _get_backend_cls(backend)
return _backend_cache[backend]
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