fix connection.Connection finalizer

finalizers execution order is not guaranteed in python3. This leads to
absence of builtins like "open" in the finalizers. Depending on the
keyring backend used inside of the set_auth_cache access to the file system
may be required.

Replace use of destructor to another builtin library "atexit" to
implement a more reliable exit handler.

Change-Id: I2d6882d64b57b65dbef086a08a3b3dc6b5faa2be

openstack/config/cloud_region.py

@@ -658,7 +658,11 @@ class CloudRegion:
         state = self._auth.get_auth_state()
 
         try:
-            keyring.set_password('openstacksdk', cache_id, state)
+            if state:
+                # NOTE: under some conditions the method may be invoked when auth
+                # is empty. This may lead to exception in the keyring lib, thus do
+                # nothing.
+                keyring.set_password('openstacksdk', cache_id, state)
         except RuntimeError:  # the fail backend raises this
             self.log.debug('Failed to set auth into keyring')
 

openstack/connection.py

@@ -176,6 +176,7 @@ try to find it and if that fails, you would create it::
 Additional information about the services can be found in the
 :ref:`service-proxies` documentation.
 """
+import atexit
 import concurrent.futures
 import warnings
 import weakref
@@ -472,9 +473,8 @@ class Connection(
                 'additional_metric_tags'
             ] = self.config.config['additional_metric_tags']
 
-    def __del__(self):
-        # try to force release of resources and save authorization
-        self.close()
+        # Register cleanup steps
+        atexit.register(self.close)
 
     @property
     def session(self):
@@ -551,9 +551,9 @@ class Connection(
 
     def close(self):
         """Release any resources held open."""
+        self.config.set_auth_cache()
         if self.__pool_executor:
             self.__pool_executor.shutdown()
-        self.config.set_auth_cache()
 
     def set_global_request_id(self, global_request_id):
         self._global_request_id = global_request_id

openstack/tests/unit/config/test_config.py

@@ -608,6 +608,21 @@ class TestConfig(base.TestCase):
         )
         ks_mock.assert_called_with(fake_auth)
 
+    @mock.patch('openstack.config.cloud_region.keyring')
+    def test_set_auth_cache_empty_auth(self, kr_mock):
+        c = config.OpenStackConfig(
+            config_files=[self.cloud_yaml], secure_files=[]
+        )
+        c._cache_auth = True
+
+        kr_mock.get_password = mock.Mock(side_effect=[RuntimeError])
+        kr_mock.set_password = mock.Mock()
+
+        region = c.get_one('_test-cloud_')
+
+        region.set_auth_cache()
+        kr_mock.set_password.assert_not_called()
+
     @mock.patch('openstack.config.cloud_region.keyring')
     def test_set_auth_cache(self, kr_mock):
         c = config.OpenStackConfig(
@@ -619,6 +634,9 @@ class TestConfig(base.TestCase):
         kr_mock.set_password = mock.Mock()
 
         region = c.get_one('_test-cloud_')
+        region._auth.set_auth_state(
+            '{"auth_token":"foo", "body":{"token":"bar"}}'
+        )
 
         region.set_auth_cache()
         kr_mock.set_password.assert_called_with(