Optimize the case of versioned image endpoint in catalog

We have version discovery for glance. However, if someone asks for a
version, and it's the version that they get from the catalog, we can
skip doing a full discovery run. Do that.

Change-Id: I2c0694ffc70bf2801de1fc187ba7b38e6a1b9d09

shade/openstackcloud.py

@@ -418,8 +418,22 @@ class OpenStackCloud(
             self._raw_clients['raw-image'] = image_client
         return self._raw_clients['raw-image']
 
+    def _match_given_image_endpoint(self, given, version):
+        if given.endswith('/'):
+            given = given[:-1]
+        if given.split('/')[-1].startswith('v' + version[0]):
+            return True
+        return False
+
     def _discover_image_endpoint(self, config_version, image_client):
         try:
+            # First - quick check to see if the endpoint in the catalog
+            # is a versioned endpoint that matches the version we requested.
+            # If it is, don't do any additoinal work.
+            catalog_endpoint = image_client.get_endpoint()
+            if self._match_given_image_endpoint(
+                    catalog_endpoint, config_version):
+                return catalog_endpoint
             # Version discovery
             versions = image_client.get('/')
             api_version = None

shade/tests/unit/base.py

@@ -401,7 +401,7 @@ class RequestsMockTestCase(BaseTestCase):
         return _RoleData(role_id, role_name, {'role': response},
                          {'role': request})
 
-    def use_keystone_v3(self):
+    def use_keystone_v3(self, catalog='catalog-v3.json'):
         self.adapter = self.useFixture(rm_fixture.Fixture())
         self.calls = []
         self._uri_registry.clear()
@@ -413,7 +413,7 @@ class RequestsMockTestCase(BaseTestCase):
                  headers={
                      'X-Subject-Token': self.getUniqueString('KeystoneToken')},
                  text=open(os.path.join(
-                     self.fixtures_directory, 'catalog-v3.json'), 'r').read()
+                     self.fixtures_directory, catalog), 'r').read()
                  )
         ])
         self._make_test_cloud(identity_api_version='3')

shade/tests/unit/fixtures/catalog-versioned-image.json

@@ -0,0 +1,71 @@
+{
+  "token": {
+    "audit_ids": [
+      "Rvn7eHkiSeOwucBIPaKdYA"
+    ],
+    "catalog": [
+      {
+        "endpoints": [
+          {
+            "id": "5a64de3c4a614d8d8f8d1ba3dee5f45f",
+            "interface": "public",
+            "region": "RegionOne",
+            "url": "https://image.example.com/v2"
+          }
+        ],
+        "name": "glance",
+        "type": "image"
+      },
+      {
+        "endpoints": [
+          {
+            "id": "4deb4d0504a044a395d4480741ba628c",
+            "interface": "public",
+            "region": "RegionOne",
+            "url": "https://identity.example.com"
+          },
+          {
+            "id": "012322eeedcd459edabb4933021112bc",
+            "interface": "admin",
+            "region": "RegionOne",
+            "url": "https://identity.example.com"
+          }
+        ],
+        "endpoints_links": [],
+        "name": "keystone",
+        "type": "identity"
+      }
+    ],
+    "expires_at": "9999-12-31T23:59:59Z",
+    "issued_at": "2016-12-17T14:25:05.000000Z",
+    "methods": [
+      "password"
+    ],
+    "project": {
+      "domain": {
+        "id": "default",
+        "name": "default"
+      },
+      "id": "1c36b64c840a42cd9e9b931a369337f0",
+      "name": "Default Project"
+    },
+    "roles": [
+      {
+        "id": "9fe2ff9ee4384b1894a90878d3e92bab",
+        "name": "_member_"
+      },
+      {
+        "id": "37071fc082e14c2284c32a2761f71c63",
+        "name": "swiftoperator"
+      }
+    ],
+    "user": {
+      "domain": {
+        "id": "default",
+        "name": "default"
+      },
+      "id": "c17534835f8f42bf98fc367e0bf35e09",
+      "name": "mordred"
+    }
+  }
+}

shade/tests/unit/test_image.py

@@ -761,3 +761,21 @@ class TestImageBrokenDiscovery(base.RequestsMockTestCase):
             self.cloud._image_client.endpoint_override,
             'https://image.example.com/v2/')
         self.assert_calls()
+
+
+class TestImageDiscoveryOptimization(base.RequestsMockTestCase):
+
+    def setUp(self):
+        super(TestImageDiscoveryOptimization, self).setUp()
+        self.use_keystone_v3(catalog='catalog-versioned-image.json')
+
+    def test_version_discovery_skip(self):
+        self.cloud.cloud_config.config['image_api_version'] = '2'
+
+        self.register_uris([
+            dict(method='GET',
+                 uri='https://image.example.com/v2/images',
+                 json={'images': []})
+        ])
+        self.assertEqual([], self.cloud.list_images())
+        self.assert_calls()