Make create_replica_method a YAML array.

Make sure the absense of this key or empty value in it is handled
correctly. Update tests and sample configuration files.

patroni/postgresql.py

@@ -240,9 +240,9 @@ class Postgresql:
         # defined by the user.  this is a list, so we need to
         # loop through all methods the user supplies
         connstring = leader.conn_url
-        # get list of replica methods from config
-        replica_list = self.config.get('create_replica_method', 'basebackup')
-        replica_methods = [rm.strip() for rm in replica_list.split(',')]
+        # get list of replica methods from config.
+        # If there is no configuration key, or no value is specified, use basebackup
+        replica_methods = self.config.get('create_replica_method') or ['basebackup']
         # go through them in priority order
         ret = 1
         for replica_method in replica_methods:

postgres0.yml

@@ -68,7 +68,9 @@ postgresql:
   admin:
     username: admin
     password: admin
-  create_replica_method: basebackup
+  create_replica_method:
+    - basebackup
+#   - wal_e
 # commented-out example for wal-e provisioning
   #create_replica_method: wal_e, basebackup
   #wal_e:

postgres1.yml

@@ -69,7 +69,10 @@ postgresql:
     username: admin
     password: admin
 # commented-out example for wal-e provisioning
-  #create_replica_method: wal_e, basebackup
+  create_replica_method:
+    - basebackup
+#   - wal_e
+# commented-out example for wal-e provisioning
   #wal_e:
     #command: /patroni/scripts/wale_restore.py
     #env_dir: /home/postgres/etc/wal-e.d/env

tests/test_postgresql.py

@@ -284,7 +284,7 @@ class TestPostgresql(unittest.TestCase):
         with patch('subprocess.call', Mock(side_effect=[Exception(), 0])):
             self.assertEquals(self.p.create_replica(self.leader, ''), 0)
 
-        self.p.config['create_replica_method'] = 'wale, basebackup'
+        self.p.config['create_replica_method'] = ['wale', 'basebackup']
         self.p.config['wale'] = {'command': 'foo'}
         with patch('subprocess.call', Mock(return_value=0)):
             self.assertEquals(self.p.create_replica(self.leader, ''), 0)