Add nofailover property to Patroni and Cluster.

Add checks for nofailover tag in is_failover_possible
in order to save on API calls for the nodes with this tag set.

patroni/__init__.py

@@ -26,6 +26,10 @@ class Patroni:
         self.ha = Ha(self)
         self.next_run = time.time()
 
+    @property
+    def nofailover(self):
+        return self.tags.get('nofailover')
+
     @staticmethod
     def get_dcs(name, config):
         if 'etcd' in config:

patroni/dcs.py

@@ -63,6 +63,10 @@ class Member(namedtuple('Member', 'index,name,session,data')):
     def api_url(self):
         return self.data.get('api_url', None)
 
+    @property
+    def nofailover(self):
+        return self.data.get('tags', {}).get('nofailover')
+
 
 class Leader(namedtuple('Leader', 'index,session,member')):
 

patroni/ha.py

@@ -169,15 +169,14 @@ class Ha:
         if self.state_handler.is_leader():
             return True
 
-        if self.patroni.tags.get('nofailover') is True:
+        if self.patroni.nofailover is True:
             return False
 
         if check_replication_lag and not self.state_handler.check_replication_lag(self.cluster.last_leader_operation):
             return False  # Too far behind last reported xlog location on master
 
         # Prepare list of nodes to run check against
-        members = [m for m in members if m.name != self.state_handler.name
-                   and not m.data.get('tags', {}).get('nofailover', None) and m.api_url]
+        members = [m for m in members if m.name != self.state_handler.name and not m.nofailover and m.api_url]
 
         if members:
             my_xlog_location = self.state_handler.xlog_position()
@@ -192,7 +191,7 @@ class Ha:
 
     def is_failover_possible(self, members):
         ret = False
-        members = [m for m in members if m.name != self.state_handler.name and m.api_url]
+        members = [m for m in members if m.name != self.state_handler.name and not m.nofailover and m.api_url]
         if members:
             for member, reachable, in_recovery, xlog_location, tags in self.fetch_nodes_statuses(members):
                 if reachable and not tags.get('nofailover'):

tests/test_ha.py

@@ -83,6 +83,7 @@ class MockPatroni:
         self.dcs = d
         self.api = Mock()
         self.tags = {}
+        self.nofailover = None
         self.api.connection_string = 'http://127.0.0.1:8008'