BUGFIX: pause on K8s (#1659)

On K8s the `Cluster.leader` is a valid object even if the cluster has no leader because we need to know the `resourceVersion` for future CAS operation. Such a non-empty object broke HA loop and made other nodes to think that the leader is there.

The right way to identify the missing leader which reliably works across all DCS is checking that the leader's name is empty.

patroni/ctl.py

@@ -225,7 +225,7 @@ def watching(w, watch, max_count=None, clear=True):
 
 def get_all_members(cluster, role='master'):
     if role == 'master':
-        if cluster.leader is not None:
+        if cluster.leader is not None and cluster.leader.name:
             yield cluster.leader
         return
 
@@ -640,7 +640,7 @@ def _do_failover_or_switchover(obj, action, cluster_name, master, candidate, for
     dcs = get_dcs(obj, cluster_name)
     cluster = dcs.get_cluster()
 
-    if action == 'switchover' and cluster.leader is None:
+    if action == 'switchover' and (cluster.leader is None or not cluster.leader.name):
         raise PatroniCtlException('This cluster has no master')
 
     if master is None:

patroni/ha.py

@@ -366,7 +366,7 @@ class Ha(object):
         elif self.patroni.replicatefrom and self.patroni.replicatefrom != self.state_handler.name:
             node_to_follow = cluster.get_member(self.patroni.replicatefrom)
         else:
-            node_to_follow = cluster.leader
+            node_to_follow = cluster.leader if cluster.leader and cluster.leader.name else None
 
         node_to_follow = node_to_follow if node_to_follow and node_to_follow.name != self.state_handler.name else None
 

tests/test_ha.py

@@ -48,7 +48,7 @@ def get_cluster_not_initialized_without_leader(cluster_config=None):
 def get_cluster_initialized_without_leader(leader=False, failover=None, sync=None, cluster_config=None):
     m1 = Member(0, 'leader', 28, {'conn_url': 'postgres://replicator:[email protected]:5435/postgres',
                                   'api_url': 'http://127.0.0.1:8008/patroni', 'xlog_location': 4})
-    leader = Leader(0, 0, m1) if leader else None
+    leader = Leader(0, 0, m1 if leader else Member(0, '', 28, {}))
     m2 = Member(0, 'other', 28, {'conn_url': 'postgres://replicator:[email protected]:5436/postgres',
                                  'api_url': 'http://127.0.0.1:8011/patroni',
                                  'state': 'running',