From 43a948e47843ee4b3fc5dfdd4080aea67c3bfdaf Mon Sep 17 00:00:00 2001
From: Steve Baker <sbaker@redhat.com>
Date: Fri, 4 Jul 2014 08:03:34 +1200
Subject: [PATCH] Use stevedore to load client plugins

This uses stevedore to load any client plugin extension defined
in the heat.clients namespace in setup.cfg.

As a transition from non-plugin to plugin clients, requesting a
named client will first search for a client plugin, then fallback
to calling the _<name>() method.

Clients plugin initialise is triggered from resources initialise.

This change also adds the clients package for the constraints
plugin manager. Custom constraints often make client API
calls and are not necessarily associated with resources, so
in many cases the client plugin will be a better place for
constraints to live.

Change-Id: I853767944caeca2939c9494ae992a0c4f6474078
---
 heat/engine/clients/__init__.py   | 37 +++++++++++++++++++++++++++++++
 heat/engine/resources/__init__.py |  3 +++
 heat/tests/test_clients.py        | 33 +++++++++++++++++++++++++--
 3 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/heat/engine/clients/__init__.py b/heat/engine/clients/__init__.py
index 801752c09c..158e389419 100644
--- a/heat/engine/clients/__init__.py
+++ b/heat/engine/clients/__init__.py
@@ -19,6 +19,7 @@ from neutronclient.v2_0 import client as neutronclient
 from novaclient import client as novaclient
 from novaclient import shell as novashell
 from oslo.config import cfg
+from stevedore import extension
 from swiftclient import client as swiftclient
 from troveclient import client as troveclient
 import warnings
@@ -45,18 +46,36 @@ class OpenStackClients(object):
     '''
     Convenience class to create and cache client instances.
     '''
+
     def __init__(self, context):
         self.context = context
         self._clients = {}
+        self._client_plugins = {}
+
+    def client_plugin(self, name):
+        global _mgr
+        if name in self._client_plugins:
+            return self._client_plugins[name]
+        if _mgr and name in _mgr.names():
+            client_plugin = _mgr[name].plugin(self)
+            self._client_plugins[name] = client_plugin
+            return client_plugin
 
     def client(self, name):
+        client_plugin = self.client_plugin(name)
+        if client_plugin:
+            return client_plugin.client()
+
         if name in self._clients:
             return self._clients[name]
+        # call the local method _<name>() if a real client plugin
+        # doesn't exist
         method_name = '_%s' % name
         if callable(getattr(self, method_name, None)):
             client = getattr(self, method_name)()
             self._clients[name] = client
             return client
+        LOG.warn(_('Requested client "%s" not found') % name)
 
     @property
     def auth_token(self):
@@ -326,3 +345,21 @@ class ClientBackend(object):
 
 
 Clients = ClientBackend
+
+
+_mgr = None
+
+
+def has_client(name):
+    return _mgr and name in _mgr
+
+
+def initialise():
+    global _mgr
+    if _mgr:
+        return
+
+    _mgr = extension.ExtensionManager(
+        namespace='heat.clients',
+        invoke_on_load=False,
+        verify_requirements=True)
diff --git a/heat/engine/resources/__init__.py b/heat/engine/resources/__init__.py
index 6c7a535abe..5a9ad8977f 100644
--- a/heat/engine/resources/__init__.py
+++ b/heat/engine/resources/__init__.py
@@ -13,6 +13,7 @@
 
 from stevedore import extension
 
+from heat.engine import clients
 from heat.engine import environment
 from heat.engine import plugin_manager
 
@@ -49,6 +50,8 @@ def initialise():
     if _environment is not None:
         return
 
+    clients.initialise()
+
     global_env = environment.Environment({}, user_env=False)
     _load_global_environment(global_env)
     _environment = global_env
diff --git a/heat/tests/test_clients.py b/heat/tests/test_clients.py
index 4c4beadf78..c3f6ace628 100644
--- a/heat/tests/test_clients.py
+++ b/heat/tests/test_clients.py
@@ -11,10 +11,10 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+from heatclient import client as heatclient
 import mock
 from oslo.config import cfg
-
-from heatclient import client as heatclient
+from testtools.testcase import skip
 
 from heat.engine import clients
 from heat.engine.clients import client_plugin
@@ -172,3 +172,32 @@ class ClientPluginTest(HeatTestCase):
         con = mock.Mock()
         c = clients.Clients(con)
         self.assertRaises(TypeError, client_plugin.ClientPlugin, c)
+
+
+class TestClientPluginsInitialise(HeatTestCase):
+
+    @skip('skipped until keystone can read context auth_ref')
+    def test_create_all_clients(self):
+        con = mock.Mock()
+        con.auth_url = "http://auth.example.com:5000/v2.0"
+        con.tenant_id = "b363706f891f48019483f8bd6503c54b"
+        con.auth_token = "3bcc3d3a03f44e3d8377f9247b0ad155"
+        c = clients.Clients(con)
+
+        for plugin_name in clients._mgr.names():
+            self.assertTrue(clients.has_client(plugin_name))
+            c.client(plugin_name)
+
+    def test_create_all_client_plugins(self):
+        plugin_types = clients._mgr.names()
+        self.assertIsNotNone(plugin_types)
+
+        con = mock.Mock()
+        c = clients.Clients(con)
+
+        for plugin_name in plugin_types:
+            plugin = c.client_plugin(plugin_name)
+            self.assertIsNotNone(plugin)
+            self.assertEqual(c, plugin.clients)
+            self.assertEqual(con, plugin.context)
+            self.assertIsNone(plugin._client)