Distinguish a bad --redis-password from any other Redis error (#11893)

python/ray/_private/services.py

@@ -608,6 +608,17 @@ def wait_for_redis_to_start(redis_ip_address, redis_port, password=None):
                 "Waiting for redis server at {}:{} to respond...".format(
                     redis_ip_address, redis_port))
             redis_client.client_list()
+        # If the Redis service is delayed getting set up for any reason, we may
+        # get a redis.ConnectionError: Error 111 connecting to host:port.
+        # Connection refused.
+        # Unfortunately, redis.ConnectionError is also the base class of
+        # redis.AuthenticationError. We *don't* want to obscure a
+        # redis.AuthenticationError, because that indicates the user provided a
+        # bad password. Thus a double except clause to ensure a
+        # redis.AuthenticationError isn't trapped here.
+        except redis.AuthenticationError as authEx:
+            raise RuntimeError("Unable to connect to Redis at {}:{}.".format(
+                redis_ip_address, redis_port)) from authEx
         except redis.ConnectionError:
             # Wait a little bit.
             time.sleep(delay)

python/ray/tests/test_ray_init.py

@@ -3,6 +3,7 @@ import pytest
 import redis
 
 import ray
+import ray._private.services
 from ray.cluster_utils import Cluster
 
 
@@ -33,6 +34,22 @@ class TestRedisPassword:
             host=redis_ip, port=redis_port, password=None)
         with pytest.raises(redis.exceptions.AuthenticationError):
             redis_client.ping()
+        # We want to simulate how this is called by ray.scripts.start().
+        try:
+            ray._private.services.wait_for_redis_to_start(
+                redis_ip, redis_port, password="wrong password")
+        # We catch a generic Exception here in case someone later changes the
+        # type of the exception.
+        except Exception as ex:
+            if not isinstance(ex.__cause__, redis.AuthenticationError):
+                raise
+            # By contrast, we may be fairly confident the exact string
+            # 'invalid password' won't go away, because redis-py simply wraps
+            # the exact error from the Redis library.
+            # https://github.com/andymccurdy/redis-py/blob/master/
+            # redis/connection.py#L132
+            if "invalid password" not in str(ex.__cause__):
+                raise
 
         # Check that we can connect to Redis using the provided password
         redis_client = redis.StrictRedis(