Enforce endpoint override for services without discovery

Services without version discovery implemented are tricky. When user is
not using endpoint_override for those there are sporadic and often
attempts to perform version discovery on every request sent [1]. It
could be prevented as much as possible on SDK side during proxy
initialization, but when a request is sent to the proxy this is still
happening inside the keystonauth library. Forcing endpoint_override for
those help avoiding that.

Touching cloud_region triggers mypy complain, so change urllib import to
keep it happy.

[1]
https://lists.openstack.org/archives/list/openstack-discuss@lists.openstack.org/thread/GBBHV2LN5S3HEUQHUQGZZ3UFEVRHQBOS/

Change-Id: I1956dfaac9ba8e3f9234cc98a36b20a330dc88f6

openstack/config/cloud_region.py

@@ -15,7 +15,7 @@
 import copy
 import os.path
 import typing as ty
-import urllib
+from urllib import parse
 import warnings
 
 try:
@@ -344,7 +344,7 @@ class CloudRegion:
     def name(self):
         if self._name is None:
             try:
-                self._name = urllib.parse.urlparse(
+                self._name = parse.urlparse(
                     self.get_session().auth.auth_url
                 ).hostname
             except Exception:
@@ -598,7 +598,7 @@ class CloudRegion:
                 interface=interface,
                 region_name=region_name,
             )
-        except keystoneauth1.exceptions.catalog.EndpointNotFound:
+        except (keystoneauth1.exceptions.catalog.EndpointNotFound, ValueError):
             return None
 
     def get_connect_retries(self, service_type):
@@ -813,7 +813,7 @@ class CloudRegion:
         if not endpoint.rstrip().rsplit('/')[-1] == 'v2.0':
             if not endpoint.endswith('/'):
                 endpoint += '/'
-            endpoint = urllib.parse.urljoin(endpoint, 'v2.0')
+            endpoint = parse.urljoin(endpoint, 'v2.0')
         return endpoint
 
     def get_session_client(

openstack/service_description.py

@@ -248,12 +248,36 @@ class ServiceDescription:
 
         # Make an adapter to let discovery take over
         version_kwargs = {}
+        supported_versions = sorted([int(f) for f in self.supported_versions])
         if version_string:
             version_kwargs['version'] = version_string
-        else:
+            if getattr(
-            supported_versions = sorted(
+                self.supported_versions[str(supported_versions[0])],
-                [int(f) for f in self.supported_versions]
+                'skip_discovery',
+                False,
+            ):
+                # Requested service does not support version discovery
+                # In this case it is more efficient to set the
+                # endpoint_override to the current catalog endpoint value,
+                # otherwise next request will try to perform discovery.
+
+                temp_adapter = config.get_session_client(self.service_type)
+                ep_override = temp_adapter.get_endpoint(skip_discovery=True)
+
+                ep_key = '{service_type}_endpoint_override'.format(
+                    service_type=self.service_type.replace('-', '_')
                 )
+                config.config[ep_key] = ep_override
+
+                return config.get_session_client(
+                    self.service_type,
+                    allow_version_hack=True,
+                    constructor=self.supported_versions[
+                        str(supported_versions[0])
+                    ],
+                    version=version_string,
+                )
+        else:
             version_kwargs['min_version'] = str(supported_versions[0])
             version_kwargs['max_version'] = '{version}.latest'.format(
                 version=str(supported_versions[-1])