Add promote() method

testgres/node.py

@@ -683,14 +683,50 @@ def reload(self, params=[]):
         _params = [
             get_bin_path("pg_ctl"),
             "-D", self.data_dir,
-            "-w",  # wait
             "reload"
         ] + params  # yapf: disable
 
         execute_utility(_params, self.utils_log_file)
 
         return self
 
+    def promote(self, dbname=None, username=None):
+        """
+        Promote standby instance to master using pg_ctl. For PostgreSQL versions
+        below 10 some additional actions required to ensure that instance
+        became writable and hence `dbname` and `username` parameters may be
+        needed.
+
+        Returns:
+            This instance of :class:`.PostgresNode`.
+        """
+
+        _params = [
+            get_bin_path("pg_ctl"),
+            "-D", self.data_dir,
+            "-w",  # wait
+            "promote"
+        ]  # yapf: disable
+
+        execute_utility(_params, self.utils_log_file)
+
+        # for versions below 10 `promote` is asynchronous so we need to wait
+        # until it actually becomes writable
+        if self._pg_version < '10':
+            check_query = "SHOW transaction_read_only"
+
+            self.poll_query_until(
+                query=check_query,
+                expected="off",
+                dbname=dbname,
+                username=username,
+                max_attempts=0)    # infinite
+
+        # node becomes master itself
+        self._master = None
+
+        return self
+
     def pg_ctl(self, params):
         """
         Invoke pg_ctl with params.

tests/test_simple.py

@@ -529,6 +529,20 @@ def test_incorrect_catchup(self):
             with self.assertRaises(TestgresException):
                 node.catchup()
 
+    def test_promotion(self):
+        with get_new_node() as master:
+            master.init().start()
+            master.safe_psql('create table abc(id serial)')
+
+            with master.replicate().start() as replica:
+                master.stop()
+                replica.promote()
+
+                # make standby becomes writable master
+                replica.safe_psql('insert into abc values (1)')
+                res = replica.safe_psql('select * from abc')
+                self.assertEqual(res, b'1\n')
+
     def test_dump(self):
         query_create = 'create table test as select generate_series(1, 2) as val'
         query_select = 'select * from test order by val asc'