Implement support of log.mode. (#3122)

There was one oversight of #2781 - to influence external tools that Patroni could execute, we set global `umask` value based on permissions of the $PGDATA directory. As a result, it also influenced permissions of log files created by Patroni.

To address the problem we implement two measures:
1. Make `log.mode` configurable.
2. If the value is not set - calculate permissions from the original value of the umask setting.

tests/test_config.py

@@ -38,6 +38,7 @@ class TestConfig(unittest.TestCase):
             'PATRONI_LOG_FORMAT': '["message", {"levelname": "level"}]',
             'PATRONI_LOG_LOGGERS': 'patroni.postmaster: WARNING, urllib3: DEBUG',
             'PATRONI_LOG_FILE_NUM': '5',
+            'PATRONI_LOG_MODE': '0123',
             'PATRONI_CITUS_DATABASE': 'citus',
             'PATRONI_CITUS_GROUP': '0',
             'PATRONI_CITUS_HOST': '0',
@@ -81,6 +82,7 @@ class TestConfig(unittest.TestCase):
             'PATRONI_POSTGRESQL_BIN_POSTGRES': 'sergtsop'
         })
         config = Config('postgres0.yml')
+        self.assertEqual(config.local_configuration['log']['mode'], 0o123)
         with patch.object(Config, '_load_config_file', Mock(return_value={'restapi': {}})):
             with patch.object(Config, '_build_effective_configuration', Mock(side_effect=Exception)):
                 config.reload_local_configuration()

tests/test_file_perm.py

@@ -30,3 +30,6 @@ class TestFilePermissions(unittest.TestCase):
     def test_set_permissions_from_data_directory(self, mock_logger):
         pg_perm.set_permissions_from_data_directory('test')
         self.assertEqual(mock_logger.call_args[0][0], 'Can not check permissions on %s: %r')
+
+    def test_orig_umask(self):
+        self.assertIsNotNone(pg_perm.orig_umask)

tests/test_log.py

@@ -38,6 +38,7 @@ class TestPatroniLogger(unittest.TestCase):
                 'traceback_level': 'DEBUG',
                 'max_queue_size': 5,
                 'dir': 'foo',
+                'mode': 0o600,
                 'file_size': 4096,
                 'file_num': 5,
                 'loggers': {
@@ -50,7 +51,9 @@ class TestPatroniLogger(unittest.TestCase):
         os.environ[Config.PATRONI_CONFIG_VARIABLE] = yaml.dump(config, default_flow_style=False)
         logger = PatroniLogger()
         patroni_config = Config(None)
-        logger.reload_config(patroni_config['log'])
+        with patch('os.chmod') as mock_chmod:
+            logger.reload_config(patroni_config['log'])
+            self.assertEqual(mock_chmod.call_args[0][1], 0o600)
         _LOG.exception('test')
         logger.start()