Fix the TTL issue of subscriptions for Redis

Currently, the TTL of subscriptons doesn't work. That said, after
the ttl seconds, the subscription can't be deleted. This pathch
fixes it and a functional test will be added in Zaqar client.

Partial-Bug: #1529168

Change-Id: I0c6a965347701bcfbf6d5634c7c8303d1e74ecc2

zaqar/storage/redis/utils.py

@@ -122,14 +122,6 @@ def descope_subscription_ids_set(subset_key):
     return (tokens[1] or None, tokens[0] or None)
 
 
-def scope_subscribers_set(queue=None, project=None,
-                          subscriber_suffix=''):
-
-    return "%s.%s.%s" % (normalize_none_str(project),
-                         normalize_none_str(queue),
-                         subscriber_suffix)
-
-
 # NOTE(prashanthr_): Aliasing the scope_message_ids_set function
 # to be used in the pools and claims controller as similar
 # functionality is required to scope redis id's.
@@ -241,12 +233,6 @@ def msg_expired_filter(message, now):
     return message.expires <= now
 
 
-def subscription_expired_filter(subscription, now):
-    """Return True if the subscription has expired."""
-
-    return subscription.expires <= now
-
-
 class QueueListCursor(object):
 
     def __init__(self, client, queues, denormalizer):
@@ -281,6 +267,12 @@ class SubscriptionListCursor(object):
     def next(self):
         curr = next(self.subscription_iter)
         subscription = self.client.hmget(curr, ['s', 'u', 't', 'o'])
+        # NOTE(flwang): The expired subscription will be removed
+        # automatically, but the key can't be deleted automatically as well.
+        # Though we clean up those expired ids when create new subscription,
+        # we still need to filter them out before a new subscription creation.
+        if not subscription[0]:
+            return self.next()
         return self.denormalizer(subscription, encodeutils.safe_decode(curr))
 
     def __next__(self):