[minigraph.py]: Add peer switch hostname to device metadata (#6405)

To make the peer switch hostname easily accessible from config DB. Add peer_switch field to DEVICE_METADATA table

Signed-off-by: Lawrence Lee <lawlee@microsoft.com>

src/sonic-config-engine/minigraph.py

@@ -1178,6 +1178,10 @@ def parse_xml(filename, platform=None, port_config_file=None, asic_name=None, hw
 
     if bool(results['PEER_SWITCH']):
         results['DEVICE_METADATA']['localhost']['subtype'] = 'DualToR'
+        if len(results['PEER_SWITCH'].keys()) > 1:
+            print("Warning: more than one peer switch was found. Only the first will be parsed: {}".format(results['PEER_SWITCH'].keys()[0]))
+
+        results['DEVICE_METADATA']['localhost']['peer_switch'] = list(results['PEER_SWITCH'].keys())[0]
 
     if is_storage_device:
         results['DEVICE_METADATA']['localhost']['storage_device'] = "true"

src/sonic-config-engine/tests/test_minigraph_case.py

@@ -57,6 +57,11 @@ def test_minigraph_subtype(self):
         output = self.run_script(argument)
         self.assertEqual(output.strip(), 'DualToR')
 
+    def test_minigraph_peer_switch_hostname(self):
+        argument = '-m "' + self.sample_graph + '" -v "DEVICE_METADATA[\'localhost\'][\'peer_switch\']"'
+        output = self.run_script(argument)
+        self.assertEqual(output.strip(), 'switch2-t0')
+
     def test_additional_json_data(self):
         argument = '-a \'{"key1":"value1"}\' -v key1'
         output = self.run_script(argument)