Fix OEM extension loading for different servers

Remove caching and re-using loaded extension objects
as it loaded the same instance for different servers
making it impossible to use it for more than 1
server.

The caching of extension managers is still in place,
consumer of loaded extension object can manage and
reuse the instance as needed.

Change-Id: I7834b49455258f4c3e5690708b23c67d6a361158
Story: 2007669
Task: 39767
(cherry picked from commit 359f2ec2c1)

releasenotes/notes/fix-oem-loading-52da045252b6c33e.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes Sushy OEM extension loading when using multiple servers that
+    caused loaded extensions to point to server for which the extension
+    was loaded first.

sushy/resources/oem/common.py

@@ -85,26 +85,6 @@ def _get_extension_manager_of_resource(resource_name):
     return _global_extn_mgrs_by_resource[resource_name]
 
 
-@utils.synchronized
-def _get_resource_vendor_extension_obj(extension, resource, vendor):
-    """Get the object returned by extension's plugin() method.
-
-    :param extension: stevedore Extension
-    :param resource: The Sushy resource instance
-    :param vendor: This is the OEM vendor string which is the vendor-specific
-        extensibility identifier. Examples are: 'Contoso', 'Hpe'. As a matter
-        of fact the lowercase of this string will be the plugin entry point
-        name.
-    :returns: The object returned by ``plugin(*args, **kwds)`` of extension.
-    """
-    if extension.obj is None:
-        oem_resource = extension.plugin()
-        extension.obj = resource.clone_resource(
-            oem_resource).set_parent_resource(resource, vendor)
-
-    return extension.obj
-
-
 def get_resource_extension_by_vendor(
         resource_name, vendor, resource):
     """Helper method to get Resource specific OEM extension object for vendor
@@ -131,7 +111,6 @@ def get_resource_extension_by_vendor(
         raise exceptions.OEMExtensionNotFoundError(
             resource=resource_name, name=vendor.lower())
 
-    if resource_vendor_extn.obj is None:
-        return _get_resource_vendor_extension_obj(
-            resource_vendor_extn, resource, vendor)
-    return resource_vendor_extn.obj
+    oem_resource = resource_vendor_extn.plugin()
+    return resource.clone_resource(
+        oem_resource).set_parent_resource(resource, vendor)

sushy/tests/unit/resources/oem/test_common.py

@@ -114,32 +114,6 @@ class ResourceOEMCommonMethodsTestCase(base.TestCase):
             self.assertTrue(extension in (self.contoso_extn,
                                           self.faux_extn))
 
-    def test__get_resource_vendor_extension_obj_lazy_plugin_invoke(self):
-        resource_instance_mock = mock.Mock()
-        extension_mock = mock.MagicMock()
-        extension_mock.obj = None
-
-        mock_oem_resource = extension_mock.plugin.return_value
-
-        result = oem_common._get_resource_vendor_extension_obj(
-            extension_mock, resource_instance_mock, 'fish-n-chips')
-
-        mock_clone_resource = resource_instance_mock.clone_resource
-        mock_clone_resource.assert_called_once_with(mock_oem_resource)
-        mock_ext = mock_clone_resource.return_value
-        mock_ext.set_parent_resource.assert_called_once_with(
-            resource_instance_mock, 'fish-n-chips')
-        mock_ext = mock_ext.set_parent_resource.return_value
-        self.assertEqual(result, mock_ext)
-
-        extension_mock.reset_mock()
-
-        # extension_mock.obj is not None anymore
-        oem_common._get_resource_vendor_extension_obj(
-            extension_mock, resource_instance_mock, 'fish-n-chips')
-
-        self.assertFalse(extension_mock.plugin.called)
-
     @mock.patch.object(stevedore, 'ExtensionManager', autospec=True)
     def test_get_resource_extension_by_vendor(self, ExtensionManager_mock):
         oem_resource_mock = mock.Mock()
@@ -192,3 +166,30 @@ class ResourceOEMCommonMethodsTestCase(base.TestCase):
             'by name "faux"',
             oem_common.get_resource_extension_by_vendor,
             'sushy.resources.system.oems', 'Faux', resource_instance_mock)
+
+    @mock.patch.object(stevedore, 'ExtensionManager', autospec=True)
+    def test_get_resource_extension_by_vendor_different_resources(
+            self, ExtensionManager_mock):
+        oem_resource_mock = mock.Mock()
+        oem_resource_mock.set_parent_resource = lambda *x: oem_resource_mock
+        resource_instance_mock = mock.Mock()
+        resource_instance_mock.clone_resource = lambda *x: oem_resource_mock
+        oem_resource_mock2 = mock.Mock()
+        oem_resource_mock2.set_parent_resource = lambda *x: oem_resource_mock2
+        resource_instance_mock2 = mock.Mock()
+        resource_instance_mock2.clone_resource = lambda *x: oem_resource_mock2
+        ExtensionManager_mock.side_effect = [self.fake_ext_mgr]
+
+        result = oem_common.get_resource_extension_by_vendor(
+            'system', 'Faux', resource_instance_mock)
+        self.assertEqual(result, oem_resource_mock)
+        ExtensionManager_mock.assert_called_once_with(
+            'sushy.resources.system.oems', propagate_map_exceptions=True,
+            on_load_failure_callback=oem_common._raise)
+        ExtensionManager_mock.reset_mock()
+
+        result2 = oem_common.get_resource_extension_by_vendor(
+            'system', 'Faux', resource_instance_mock2)
+        self.assertEqual(result2, oem_resource_mock2)
+        ExtensionManager_mock.assert_not_called()
+        ExtensionManager_mock.reset_mock()