Fix matchmaker_redis ack_alive fails with KeyError

Fix matchmaker_redis: ack_alive fails with KeyError on re-registration
attempt.

def ack_alive(self, key, host):
    topic = "%s.%s" % (key, host)
    if not self.redis.expire(topic, CONF.matchmaker_heartbeat_ttl):
        # If we could not update the expiration, the key
        # might have been pruned. Re-register, creating a new
        # key in Redis.
        self.register(self.host_topic[host], host)

self.host_topic is a dict with keys of tuple (key, host), not 'host',
register's first parameter is the topic like 'notification-info',
so modify it to key.
And it will not cause indefinite recursion, because when register end,
the key exist in redis, redis.expire will return True.

Add test case for ack_alive.

Closes-Bug: #1419718

Change-Id: I8d972afe89aec02a5c8f0d9dd4e216bc12c298a1

oslo_messaging/_drivers/matchmaker_redis.py

@@ -105,7 +105,7 @@ class MatchMakerRedis(mm_common.HeartbeatMatchMakerBase):
             # If we could not update the expiration, the key
             # might have been pruned. Re-register, creating a new
             # key in Redis.
-            self.register(self.host_topic[host], host)
+            self.register(key, host)
 
     def is_alive(self, topic, host):
         if self.redis.ttl(host) == -1:

oslo_messaging/tests/drivers/test_matchmaker_redis.py

@@ -81,3 +81,9 @@ class RedisMatchMakerTest(test_utils.BaseTestCase):
         self.assertEqual(
             sorted(self.matcher.redis.smembers('conductor')),
             ['conductor.node1', 'conductor.node2', 'conductor.node3'])
+
+    def test_ack_alive(self):
+        self.matcher.ack_alive('ack_alive', 'controller1')
+        self.assertEqual(
+            sorted(self.matcher.redis.smembers('ack_alive')),
+            ['ack_alive.controller1'])