Add CLI for configuring synchronous mode (sonic-net#1094)

* Add CLI for configuring synchronous mode

* Integrate switch for sync mode as a config CLI

* Add unit test

config/main.py

@@ -1238,6 +1238,31 @@ def hostname(new_hostname):
         raise
     click.echo("Please note loaded setting will be lost after system reboot. To preserve setting, run `config save`.")
 
+#
+# 'synchronous_mode' command ('config synchronous_mode ...')
+#
+@config.command('synchronous_mode')
+@click.argument('sync_mode', metavar='<enable|disable>', required=True)
+def synchronous_mode(sync_mode):
+    """ Enable or disable synchronous mode between orchagent and syncd \n
+        swss restart required to apply the configuration \n
+        Options to restart swss and apply the configuration: \n
+            1. config save -y \n
+               config reload -y \n
+            2. systemctl restart swss
+    """
+
+    if sync_mode == 'enable' or sync_mode == 'disable':
+        config_db = ConfigDBConnector()
+        config_db.connect()
+        config_db.mod_entry('DEVICE_METADATA' , 'localhost', {"synchronous_mode" : sync_mode})
+        click.echo("""Wrote %s synchronous mode into CONFIG_DB, swss restart required to apply the configuration: \n
+    Option 1. config save -y \n
+              config reload -y \n
+    Option 2. systemctl restart swss""" % sync_mode)
+    else:
+        raise click.BadParameter("Error: Invalid argument %s, expect either enable or disable" % sync_mode)
+
 #
 # 'portchannel' group ('config portchannel ...')
 #

tests/synchronous_mode_test.py

@@ -0,0 +1,37 @@
+from click.testing import CliRunner
+import config.main as config
+
+class TestSynchronousMode(object):
+    @classmethod
+    def setup_class(cls):
+        print("SETUP")
+
+    def __check_result(self, result_msg, mode):
+        if mode == "enable" or mode == "disable":
+            expected_msg = """Wrote %s synchronous mode into CONFIG_DB, swss restart required to apply the configuration: \n
+    Option 1. config save -y \n
+              config reload -y \n
+    Option 2. systemctl restart swss""" % mode
+        else:
+            expected_msg = "Error: Invalid argument %s, expect either enable or disable" % mode
+
+        return expected_msg in result_msg
+
+
+    def test_synchronous_mode(self):
+        runner = CliRunner()
+
+        result = runner.invoke(config.config.commands["synchronous_mode"], ["enable"])
+        print(result.output)
+        assert result.exit_code == 0
+        assert self.__check_result(result.output, "enable")
+
+        result = runner.invoke(config.config.commands["synchronous_mode"], ["disable"])
+        print(result.output)
+        assert result.exit_code == 0
+        assert self.__check_result(result.output, "disable")
+
+        result = runner.invoke(config.config.commands["synchronous_mode"], ["invalid-input"])
+        print(result.output)
+        assert result.exit_code != 0
+        assert self.__check_result(result.output, "invalid-input")