Keyston Session can be used to instantiate client

The session is used to fetch the almanach url from keystone

Change-Id: I7122c5870624985dc122a9b78ffebdb4a925235d

almanachclient/http_client.py

@@ -26,8 +26,27 @@ logger = logging.getLogger(__name__)
 
 class HttpClient(metaclass=abc.ABCMeta):
 
-    def __init__(self, url, token=None):
-        self.url = url
+    def __init__(self, url=None, token=None,
+                 session=None, region_name=None,
+                 service_type='cloudmetrics', endpoint_type=None):
+        """Initialization of Client object.
+
+        :param string url: The endpoint of the Almanach service. Overrides the session url.
+        :param string token: The Almanach X-Auth-Token.
+        :param session: A session object that can be used for communication.
+        :type session: keystonauth.session.Session
+        :param string region_name:
+        :param string service_type:
+        :param string endpoint_type:
+        """
+        if not url and not session:
+            raise ValueError('A session or an endpoint must be provided')
+
+        if session:
+            self.url = session.get_endpoint(service_type=service_type, region_name=region_name, interface=endpoint_type)
+        if url:
+            self.url = url
+
         self.token = token
 
     def _get(self, url, params=None):

almanachclient/tests/v1/test_client.py

@@ -37,6 +37,26 @@ class TestClient(base.TestCase):
 
         self.client = Client(self.url, self.token)
 
+        self.session = mock.Mock()
+        self.session.get_endpoint.return_value = 'http://almanach_url/from/session'
+
+    def test_instantiate_client_with_a_session(self):
+        client = Client(session=self.session)
+
+        self.assertEqual('http://almanach_url/from/session', client.get_url())
+
+        self.session.get_endpoint.called_once_with(service_type='cloudmetrics', region_name=None, interface=None)
+
+    def test_instantiate_client_endpoint_url_override_session_url(self):
+        client = Client(url='http://almanach_url', session=self.session)
+
+        self.assertEqual('http://almanach_url', client.get_url())
+
+        self.session.get_endpoint.called_once_with(service_type='cloudmetrics', region_name=None, interface=None)
+
+    def test_instantiate_client_no_url_and_no_session(self):
+        self.assertRaises(ValueError, Client)
+
     @mock.patch('requests.get')
     def test_get_info(self, requests):
         expected = {

doc/source/usage_api.rst

@@ -9,10 +9,22 @@ Almanach Python API
 Usage
 -----
 
-First, create an Almanach Client instance with your credentials::
+First, create an Almanach Client instance by providing a Keystone session and your AUTH_TOKEN::
 
+    >>> from keystoneauth1 import loading
+    >>> from keystoneauth1 import session
     >>> from almanachclient.v1.client import Client
-    >>> almanach = Client(ALMANACH_URL, AUTH_TOKEN)
+
+    >>> loader = loading.get_plugin_loader('password')
+    >>> auth = loader.load_from_options(auth_url=AUTH_URL,
+    ...                                 username=USERNAME,
+    ...                                 password=PASSWORD,
+    ...                                 project_name=PROJECT_NAME,
+    ...                                 project_domain_name="Default",
+    ...                                 user_domain_name="Default")
+    >>> sess = session.Session(auth=auth)
+
+    >>> almanach = Client(session=sess, token=AUTH_TOKEN)
 
 Here ``ALMANACH_URL`` will be a string that represents the url of Almanach API.
 ``AUTH_TOKEN`` will be the authorization token you use to access the API.