Don't fail if a provider driver cannot be loaded in Octavia API

Fix an issue that prevents the Octavia API service to be correctly
initialized when it fails to load a provider driver.

When enabled_provider_drivers setting is not correctly configured (ex:
if it contains a non existing driver) or when a provider driver fails
to load, the exception was not caught by the Octavia API service, so the
service was not properly configured and the whole Octavia API was
unreachable.

Now the Octavia API service skips the driver initialization in case of
errors, removes the driver(s) from the enabled list, and the other
provider drivers are functional.

Story 2008710
Task 42044

Depends-on: https://review.opendev.org/c/openstack/octavia/+/964892
Change-Id: I34341e1aaad1524e3e0834309c5f6897f176af53
Signed-off-by: Zachary Raines <zachary.raines@canonical.com>

octavia/api/app.py

@@ -44,8 +44,20 @@ def get_pecan_config():
 
 def _init_drivers():
     """Initialize provider drivers."""
-    for provider in CONF.api_settings.enabled_provider_drivers:
-        driver_factory.get_driver(provider)
+    providers_to_remove = []
+    enabled_providers = driver_factory.get_providers()
+    for provider in enabled_providers:
+        try:
+            driver_factory.get_driver(provider)
+        except Exception:
+            LOG.exception("Cannot load driver '%s', will remove from "
+                          "service. Please check "
+                          "[api_settings]/enabled_provider_drivers in "
+                          "octavia.conf for correctness.", provider)
+            providers_to_remove.append(provider)
+
+    if providers_to_remove:
+        driver_factory.remove_providers(providers_to_remove)
 
 
 def setup_app(pecan_config=None, debug=False, argv=None):

octavia/api/drivers/driver_factory.py

@@ -48,3 +48,14 @@ def get_driver(provider):
                   provider, str(e))
         raise exceptions.ProviderNotFound(prov=provider)
     return driver
+
+
+def remove_providers(providers):
+    # Presumably these provider drivers failed to load, remove so they do not
+    # show up in the available list
+    for provider in providers:
+        CONF.api_settings.enabled_provider_drivers.pop(provider)
+
+
+def get_providers():
+    return CONF.api_settings.enabled_provider_drivers

octavia/api/v2/controllers/provider.py

@@ -13,7 +13,6 @@
 #    under the License.
 
 from octavia_lib.api.drivers import exceptions as lib_exceptions
-from oslo_config import cfg
 from oslo_log import log as logging
 from pecan import expose as pecan_expose
 from pecan import request as pecan_request
@@ -26,7 +25,6 @@ from octavia.api.v2.types import provider as provider_types
 from octavia.common import constants
 from octavia.common import exceptions
 
-CONF = cfg.CONF
 LOG = logging.getLogger(__name__)
 
 
@@ -46,7 +44,7 @@ class ProviderController(base.BaseController):
         self._auth_validate_action(context, context.project_id,
                                    constants.RBAC_GET_ALL)
 
-        enabled_providers = CONF.api_settings.enabled_provider_drivers
+        enabled_providers = driver_factory.get_providers()
         response_list = [
             provider_types.ProviderResponse(name=key, description=value) for
             key, value in enabled_providers.items()]

octavia/tests/unit/api/test_app.py

@@ -0,0 +1,54 @@
+#    Copyright 2021 Red Hat, Inc. All rights reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from unittest import mock
+
+from oslo_config import cfg
+from oslo_config import fixture as oslo_fixture
+
+from octavia.api import app
+from octavia.api.drivers import driver_factory
+import octavia.tests.unit.base as base
+
+
+class TestApp(base.TestCase):
+
+    def setUp(self):
+        super().setUp()
+
+    @mock.patch.object(driver_factory, "get_driver")
+    def test__init_drivers(self, mock_get_driver):
+        self.CONF = self.useFixture(oslo_fixture.Config(cfg.CONF))
+        self.CONF.config(
+            group="api_settings",
+            enabled_provider_drivers="provider1:desc1,provider2:desc2")
+
+        app._init_drivers()
+        mock_get_driver.assert_any_call("provider1")
+        mock_get_driver.assert_any_call("provider2")
+
+    @mock.patch.object(driver_factory, "get_driver")
+    def test__init_drivers_with_error(self, mock_get_driver):
+        self.CONF = self.useFixture(oslo_fixture.Config(cfg.CONF))
+        self.CONF.config(
+            group="api_settings",
+            enabled_provider_drivers="provider1:desc1,provider2:desc2")
+
+        mock_get_driver.side_effect = [True, Exception('Internal Error')]
+
+        app._init_drivers()
+        mock_get_driver.assert_any_call("provider1")
+        mock_get_driver.assert_any_call("provider2")
+        enabled_providers = driver_factory.get_providers()
+        self.assertEqual(enabled_providers, {'provider1': 'desc1'})

releasenotes/notes/fix-octavia-api-driver-init-68b634549c12da6e.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fix an issue that prevents the Octavia API service to be correctly
+    initialized when it fails to load a provider driver. It will now
+    fail gracefully and remove the driver from the enabled list.