Add PostgresNode.promote() method which promotes standby node to master

Author: zilder

testgres/node.py

@@ -670,6 +670,28 @@ def reload(self, params=[]):
 
         return self
 
+    def promote(self):
+        """
+        Promote standby instance to master using pg_ctl.
+
+        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)
+
+        # Node becomes master itself
+        self._master = None
+
+        return self
+
     def pg_ctl(self, params):
         """
         Invoke pg_ctl with params.

tests/test_simple.py

@@ -407,6 +407,20 @@ 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'