Check context before returning cached value

The key manager caches the value of barbican client to be reused,
saving an extra call to keystone.  The cached value is only
applicable to the current context, so the context must be checked
before returning the cached value.

Change-Id: Ib10909a098fb2cd070129c239b6d3b95edc8fea0
Closes-Bug: #1523646

cinder/keymgr/barbican.py

@@ -49,6 +49,7 @@ class BarbicanKeyManager(key_mgr.KeyManager):
         self._base_url = CONF.keymgr.encryption_api_url
         self._parse_barbican_api_url()
         self._barbican_client = None
+        self._current_context = None
 
     def _parse_barbican_api_url(self):
         """Setup member variables to reference the Barbican URL.
@@ -84,7 +85,6 @@ class BarbicanKeyManager(key_mgr.KeyManager):
                                  or project_id is None
         """
 
-        if not self._barbican_client:
         # Confirm context is provided, if not raise not authorized
         if not ctxt:
             msg = _("User is not authorized to use key manager.")
@@ -96,6 +96,10 @@ class BarbicanKeyManager(key_mgr.KeyManager):
             LOG.error(msg)
             raise exception.KeyManagerError(msg)
 
+        # If same context, return cached barbican client
+        if self._barbican_client and self._current_context == ctxt:
+            return self._barbican_client
+
         try:
             auth = identity.v3.Token(
                 auth_url=CONF.keymgr.encryption_auth_url,
@@ -105,6 +109,7 @@ class BarbicanKeyManager(key_mgr.KeyManager):
             self._barbican_client = barbican_client.Client(
                 session=sess,
                 endpoint=self._barbican_endpoint)
+            self._current_context = ctxt
         except Exception:
             with excutils.save_and_reraise_exception():
                 LOG.exception(_LE("Error creating Barbican client."))

cinder/tests/unit/keymgr/test_barbican.py

@@ -78,6 +78,7 @@ class BarbicanKeyManagerTestCase(test_key_mgr.KeyManagerTestCase):
         self.create = self.mock_barbican.secrets.create
 
         self.key_mgr._barbican_client = self.mock_barbican
+        self.key_mgr._current_context = self.ctxt
 
     def _build_mock_symKey(self):
         self.mock_symKey = mock.Mock()