Forgot to pass CARROT_BACKEND in establish_connection, also BROKER_BACKEND now alias to CARROT_BACKEND.

celery/conf.py

@@ -40,9 +40,9 @@ _DEFAULTS = {
     "CELERY_DEFAULT_EXCHANGE": "celery",
     "CELERY_DEFAULT_EXCHANGE_TYPE": "direct",
     "CELERY_DEFAULT_DELIVERY_MODE": 2, # persistent
-    "CELERY_BROKER_CONNECTION_TIMEOUT": 4,
-    "CELERY_BROKER_CONNECTION_RETRY": True,
-    "CELERY_BROKER_CONNECTION_MAX_RETRIES": 100,
+    "BROKER_CONNECTION_TIMEOUT": 4,
+    "BROKER_CONNECTION_RETRY": True,
+    "BROKER_CONNECTION_MAX_RETRIES": 100,
     "CELERY_ACKS_LATE": False,
     "CELERYD_POOL_PUTLOCKS": True,
     "CELERYD_POOL": "celery.concurrency.processes.TaskPool",
@@ -173,6 +173,7 @@ BROKER_CONNECTION_RETRY = _get("BROKER_CONNECTION_RETRY",
                                 compat=["CELERY_BROKER_CONNECTION_RETRY"])
 BROKER_CONNECTION_MAX_RETRIES = _get("BROKER_CONNECTION_MAX_RETRIES",
                             compat=["CELERY_BROKER_CONNECTION_MAX_RETRIES"])
+BROKER_BACKEND = _get("BROKER_BACKEND") or _get("CARROT_BACKEND")
 
 # <--- Message routing                             <-   --   --- - ----- -- #
 DEFAULT_QUEUE = _get("CELERY_DEFAULT_QUEUE")

celery/messaging.py

@@ -221,7 +221,7 @@ class BroadcastConsumer(Consumer):
 
 def establish_connection(hostname=None, userid=None, password=None,
         virtual_host=None, port=None, ssl=None, insist=None,
-        connect_timeout=None):
+        connect_timeout=None, backend_cls=None):
     """Establish a connection to the message broker."""
     if insist is None:
         insist = conf.BROKER_INSIST
@@ -235,6 +235,7 @@ def establish_connection(hostname=None, userid=None, password=None,
                             password or conf.BROKER_PASSWORD,
                             virtual_host or conf.BROKER_VHOST,
                             port or conf.BROKER_PORT,
+                            backend_cls=backend_cls or conf.BROKER_BACKEND,
                             insist=insist, ssl=ssl,
                             connect_timeout=connect_timeout)