Versioned Endpoint hack for Sessions

To maintain compatibility we must allow people to specify a versioned
URL in the service catalog but allow the plugins to return a different
URL to users.

We need this to be a general approach as other services will likely have
a similar problem with their catalog.

The expectation here is that a client will register the catalog hack at
import time rather than for every request.

Closes-Bug: #1335726
Change-Id: I244f0ec3acca39fd1b2a2c5883abc06ec10eddc7

5 files changed, 198 insertions, 1 deletions

diff --git a/keystoneclient/_discover.py b/keystoneclient/_discover.py
index 7ea396f..c9c9792 100644
--- a/keystoneclient/_discover.py
+++ b/keystoneclient/_discover.py
@@ -22,6 +22,7 @@ raw data specified in version discovery responses.
 """
 
 import logging
+import re
 
 from keystoneclient import exceptions
 from keystoneclient import utils
@@ -262,3 +263,56 @@ class Discover(object):
         """
         data = self.data_for(version, **kwargs)
         return data['url'] if data else None
+
+
+class _VersionHacks(object):
+    """A container to abstract the list of version hacks.
+
+    This could be done as simply a dictionary but is abstracted like this to
+    make for easier testing.
+    """
+
+    def __init__(self):
+        self._discovery_data = {}
+
+    def add_discover_hack(self, service_type, old, new=''):
+        """Add a new hack for a service type.
+
+        :param str service_type: The service_type in the catalog.
+        :param re.RegexObject old: The pattern to use.
+        :param str new: What to replace the pattern with.
+        """
+        hacks = self._discovery_data.setdefault(service_type, [])
+        hacks.append((old, new))
+
+    def get_discover_hack(self, service_type, url):
+        """Apply the catalog hacks and figure out an unversioned endpoint.
+
+        :param str service_type: the service_type to look up.
+        :param str url: The original url that came from a service_catalog.
+
+        :return: Either the unversioned url or the one from the catalog to try.
+        """
+        for old, new in self._discovery_data.get(service_type, []):
+            new_string, number_of_subs_made = old.subn(new, url)
+            if number_of_subs_made > 0:
+                return new_string
+
+        return url
+
+
+_VERSION_HACKS = _VersionHacks()
+_VERSION_HACKS.add_discover_hack('identity', re.compile('/v2.0/?$'), '/')
+
+
+def get_catalog_discover_hack(service_type, url):
+    """Apply the catalog hacks and figure out an unversioned endpoint.
+
+    This function is internal to keystoneclient.
+
+    :param str service_type: the service_type to look up.
+    :param str url: The original url that came from a service_catalog.
+
+    :return: Either the unversioned url or the one from the catalog to try.
+    """
+    return _VERSION_HACKS.get_discover_hack(service_type, url)
diff --git a/keystoneclient/auth/identity/base.py b/keystoneclient/auth/identity/base.py
index 8069e5c..10a9fe8 100644
--- a/keystoneclient/auth/identity/base.py
+++ b/keystoneclient/auth/identity/base.py
@@ -201,8 +201,15 @@ class BaseIdentityPlugin(base.BaseAuthPlugin):
             # defaulting to the most recent version.
             return url
 
+        # NOTE(jamielennox): For backwards compatibility people might have a
+        # versioned endpoint in their catalog even though they want to use
+        # other endpoint versions. So we support a list of client defined
+        # situations where we can strip the version component from a URL before
+        # doing discovery.
+        hacked_url = _discover.get_catalog_discover_hack(service_type, url)
+
         try:
-            disc = self.get_discovery(session, url, authenticated=False)
+            disc = self.get_discovery(session, hacked_url, authenticated=False)
         except (exceptions.DiscoveryFailure,
                 exceptions.HTTPError,
                 exceptions.ConnectionError):
diff --git a/keystoneclient/discover.py b/keystoneclient/discover.py
index 07de97d..982683a 100644
--- a/keystoneclient/discover.py
+++ b/keystoneclient/discover.py
@@ -266,3 +266,34 @@ class Discover(_discover.Discover):
         """
         version_data = self._calculate_version(version, unstable)
         return self._create_client(version_data, **kwargs)
+
+
+def add_catalog_discover_hack(service_type, old, new):
+    """Adds a version removal rule for a particular service.
+
+    Originally deployments of OpenStack would contain a versioned endpoint in
+    the catalog for different services. E.g. an identity service might look
+    like ``http://localhost:5000/v2.0``. This is a problem when we want to use
+    a different version like v3.0 as there is no way to tell where it is
+    located. We cannot simply change all service catalogs either so there must
+    be a way to handle the older style of catalog.
+
+    This function adds a rule for a given service type that if part of the URL
+    matches a given regular expression in *old* then it will be replaced with
+    the *new* value. This will replace all instances of old with new. It should
+    therefore contain a regex anchor.
+
+    For example the included rule states::
+
+        add_catalog_version_hack('identity', re.compile('/v2.0/?$'), '/')
+
+    so if the catalog retrieves an *identity* URL that ends with /v2.0 or
+    /v2.0/ then it should replace it simply with / to fix the user's catalog.
+
+    :param str service_type: The service type as defined in the catalog that
+                             the rule will apply to.
+    :param re.RegexObject old: The regular expression to search for and replace
+                               if found.
+    :param str new: The new string to replace the pattern with.
+    """
+    _discover._VERSION_HACKS.add_discover_hack(service_type, old, new)
diff --git a/keystoneclient/tests/auth/test_identity_common.py b/keystoneclient/tests/auth/test_identity_common.py
index 371fd18..9a369f7 100644
--- a/keystoneclient/tests/auth/test_identity_common.py
+++ b/keystoneclient/tests/auth/test_identity_common.py
@@ -286,3 +286,71 @@ class V2(CommonIdentityTests, utils.TestCase):
 
     def stub_auth(self, **kwargs):
         self.stub_url('POST', ['tokens'], **kwargs)
+
+
+class CatalogHackTests(utils.TestCase):
+
+    TEST_URL = 'http://keystone.server:5000/v2.0'
+    OTHER_URL = 'http://other.server:5000/path'
+
+    IDENTITY = 'identity'
+
+    BASE_URL = 'http://keystone.server:5000/'
+    V2_URL = BASE_URL + 'v2.0'
+    V3_URL = BASE_URL + 'v3'
+
+    def test_getting_endpoints(self):
+        disc = fixture.DiscoveryList(href=self.BASE_URL)
+        self.stub_url('GET',
+                      ['/'],
+                      base_url=self.BASE_URL,
+                      json=disc)
+
+        token = fixture.V2Token()
+        service = token.add_service(self.IDENTITY)
+        service.add_endpoint(public=self.V2_URL,
+                             admin=self.V2_URL,
+                             internal=self.V2_URL)
+
+        self.stub_url('POST',
+                      ['tokens'],
+                      base_url=self.V2_URL,
+                      json=token)
+
+        v2_auth = v2.Password(self.V2_URL,
+                              username=uuid.uuid4().hex,
+                              password=uuid.uuid4().hex)
+
+        sess = session.Session(auth=v2_auth)
+
+        endpoint = sess.get_endpoint(service_type=self.IDENTITY,
+                                     interface='public',
+                                     version=(3, 0))
+
+        self.assertEqual(self.V3_URL, endpoint)
+
+    def test_returns_original_when_discover_fails(self):
+        token = fixture.V2Token()
+        service = token.add_service(self.IDENTITY)
+        service.add_endpoint(public=self.V2_URL,
+                             admin=self.V2_URL,
+                             internal=self.V2_URL)
+
+        self.stub_url('POST',
+                      ['tokens'],
+                      base_url=self.V2_URL,
+                      json=token)
+
+        self.stub_url('GET', [], base_url=self.BASE_URL, status_code=404)
+
+        v2_auth = v2.Password(self.V2_URL,
+                              username=uuid.uuid4().hex,
+                              password=uuid.uuid4().hex)
+
+        sess = session.Session(auth=v2_auth)
+
+        endpoint = sess.get_endpoint(service_type=self.IDENTITY,
+                                     interface='public',
+                                     version=(3, 0))
+
+        self.assertEqual(self.V2_URL, endpoint)
diff --git a/keystoneclient/tests/test_discovery.py b/keystoneclient/tests/test_discovery.py
index 10f1c2f..811e65c 100644
--- a/keystoneclient/tests/test_discovery.py
+++ b/keystoneclient/tests/test_discovery.py
@@ -10,6 +10,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import re
 import uuid
 
 import six
@@ -772,6 +773,42 @@ class DiscoverQueryTests(utils.TestCase):
         self.assertEqual(1, len(versions))
 
 
+class CatalogHackTests(utils.TestCase):
+
+    TEST_URL = 'http://keystone.server:5000/v2.0'
+    OTHER_URL = 'http://other.server:5000/path'
+
+    IDENTITY = 'identity'
+
+    BASE_URL = 'http://keystone.server:5000/'
+    V2_URL = BASE_URL + 'v2.0'
+    V3_URL = BASE_URL + 'v3'
+
+    def setUp(self):
+        super(CatalogHackTests, self).setUp()
+        self.hacks = _discover._VersionHacks()
+        self.hacks.add_discover_hack(self.IDENTITY,
+                                     re.compile('/v2.0/?$'),
+                                     '/')
+
+    def test_version_hacks(self):
+        self.assertEqual(self.BASE_URL,
+                         self.hacks.get_discover_hack(self.IDENTITY,
+                                                      self.V2_URL))
+
+        self.assertEqual(self.BASE_URL,
+                         self.hacks.get_discover_hack(self.IDENTITY,
+                                                      self.V2_URL + '/'))
+
+        self.assertEqual(self.OTHER_URL,
+                         self.hacks.get_discover_hack(self.IDENTITY,
+                                                      self.OTHER_URL))
+
+    def test_ignored_non_service_type(self):
+        self.assertEqual(self.V2_URL,
+                         self.hacks.get_discover_hack('other', self.V2_URL))
+
+
 class DiscoverUtils(utils.TestCase):
 
     def test_version_number(self):