Code refactoring per review by Alex Shulgin.

In particular, rename most of the functions that have leader
in the name if they can be called in the context where the
leader is None.

patroni/dcs.py

@@ -112,7 +112,7 @@ class Cluster(namedtuple('Cluster', 'initialize,leader,last_leader_operation,mem
         return not (self.leader and self.leader.name)
 
     def has_member(self, member_name):
-        return len([m for m in self.members if m.name == member_name]) > 0
+        return any(m for m in self.members if m.name == member_name)
 
 
 class AbstractDCS:

patroni/ha.py

@@ -62,7 +62,7 @@ class Ha:
                 pass
         self.dcs.touch_member(json.dumps(data, separators=(',', ':')))
 
-    def copy_backup_from_leader(self, leader):
+    def clone(self, leader):
         if self.state_handler.bootstrap(cluster_initialized=True, current_leader=leader):
             logger.info('bootstrapped from leader' if leader else 'bootstrapped without leader')
         else:
@@ -73,7 +73,7 @@ class Ha:
     def bootstrap(self):
         if not self.cluster.is_unlocked():  # cluster already has leader
             self._async_executor.schedule('bootstrap from leader')
-            self._async_executor.run_async(self.copy_backup_from_leader, args=(self.cluster.leader, ))
+            self._async_executor.run_async(self.clone, args=(self.cluster.leader, ))
             return 'trying to bootstrap from leader'
         elif not self.cluster.initialize and not self.patroni.nofailover:  # no initialize key
             if self.dcs.initialize(create_new=True):  # race for initialization
@@ -93,7 +93,7 @@ class Ha:
                 return 'failed to acquire initialize lock'
         else:
             if self.state_handler.can_create_replica_without_leader():
-                self._async_executor.run_async(self.copy_backup_from_leader, args=(None, ))
+                self._async_executor.run_async(self.clone, args=(None, ))
                 return "trying to bootstrap without leader"
             return 'waiting for leader to bootstrap'
 
@@ -120,7 +120,7 @@ class Ha:
             node_to_follow = node_to_follow[0] if node_to_follow else self.cluster.leader
         else:
             node_to_follow = self.cluster.leader
-        node_to_follow = None if (node_to_follow and node_to_follow.name) == self.state_handler.name else node_to_follow
+        node_to_follow = None if node_to_follow and node_to_follow.name == self.state_handler.name else node_to_follow
         if not self.state_handler.check_recovery_conf(node_to_follow) or recovery:
             self._async_executor.schedule('changing primary_conninfo and restarting')
             self._async_executor.run_async(self.state_handler.follow, (node_to_follow, recovery))
@@ -350,7 +350,7 @@ class Ha:
     def reinitialize(self, cluster):
         self.state_handler.stop('immediate')
         self.state_handler.remove_data_directory()
-        self.copy_backup_from_leader(cluster.leader)
+        self.clone(cluster.leader)
 
     def process_scheduled_action(self):
         if self.reinitialize_scheduled():

patroni/postgresql.py

@@ -219,7 +219,7 @@ class Postgresql:
         env['PGPASSFILE'] = self.pgpass
         return env
 
-    def sync_from_leader(self, leader):
+    def sync_replica(self, leader):
         if leader:
             r = parseurl(leader.conn_url)
         env = self.write_pgpass(r) if leader else os.environ.copy()
@@ -657,8 +657,8 @@ $$""".format(name, options), name, password, password)
                 # master), or if replicatefrom destination member happens to be the current master
                 if self.role == 'master':
                     slots = [m.name for m in cluster.members if m.name != self.name and
-                             (not cluster.has_member(m.replicatefrom)
-                              if m.replicatefrom and m.replicatefrom != self.name else True)]
+                             (m.replicatefrom is None or m.replicatefrom == self.name or
+                              not cluster.has_member(m.replicatefrom))]
                 else:
                     # only manage slots for replicas that want to replicate from this one
                     slots = [m.name for m in cluster.members if m.replicatefrom == self.name]
@@ -711,7 +711,7 @@ $$""".format(name, options), name, password, password)
             else:
                 raise PostgresException("Could not bootstrap master PostgreSQL")
         else:
-            if self.sync_from_leader(current_leader):
+            if self.sync_replica(current_leader):
                 self.restore_configuration_files()
                 self.write_recovery_conf(current_leader, True)
                 ret = self.start()

tests/test_postgresql.py

@@ -229,8 +229,8 @@ class TestPostgresql(unittest.TestCase):
         self.p.write_pgpass({'host': 'localhost', 'port': '5432', 'user': 'foo', 'password': 'bar'})
 
     @patch('patroni.postgresql.Postgresql.write_pgpass', MagicMock(return_value=dict()))
-    def test_sync_from_leader(self):
-        self.assertTrue(self.p.sync_from_leader(self.leader))
+    def test_sync_replica(self):
+        self.assertTrue(self.p.sync_replica(self.leader))
 
     @patch('subprocess.call', side_effect=Exception("Test"))
     @patch('patroni.postgresql.Postgresql.write_pgpass', MagicMock(return_value=dict()))
@@ -370,7 +370,7 @@ class TestPostgresql(unittest.TestCase):
         with patch('subprocess.call', Mock(return_value=1)):
             self.assertRaises(PostgresException, self.p.bootstrap)
         self.p.bootstrap()
-        with patch('patroni.postgresql.Postgresql.sync_from_leader', MagicMock(return_value=True)):
+        with patch('patroni.postgresql.Postgresql.sync_replica', MagicMock(return_value=True)):
             self.p.bootstrap(self.leader)
 
     def test_remove_data_directory(self):