Refactor server password metadata to avoid direct db usage

This refactors the set_password() method in the server_password
API extension to merely format the metadata and return it, leaving
the job of updating the database to the caller. In the API extension
case, the update can be done immediately against the database as
before. In the case of the metadata API handler and the xenapi virt
driver making the call, conductor can be used to update the instance's
system_metadata, thereby avoiding a direct database access.

Related to blueprint no-db-compute

Change-Id: I0563feaa97d768a96f950c148b1dbf51c356c4ac

2 files changed, 15 insertions, 8 deletions

diff --git a/nova/api/metadata/password.py b/nova/api/metadata/password.py
index b2bb83b15..f3453e945 100644
--- a/nova/api/metadata/password.py
+++ b/nova/api/metadata/password.py
@@ -15,8 +15,9 @@
 
 from webob import exc
 
+from nova import conductor
 from nova import context
-from nova import db
+from nova import utils
 
 
 CHUNKS = 4
@@ -33,7 +34,7 @@ def extract_password(instance):
     return result or None
 
 
-def set_password(context, instance_uuid, password):
+def convert_password(context, password):
     """Stores password as system_metadata items.
 
     Password is stored with the keys 'password_0' -> 'password_3'.
@@ -43,10 +44,7 @@ def set_password(context, instance_uuid, password):
     for i in xrange(CHUNKS):
         meta['password_%d' % i] = password[:CHUNK_LENGTH]
         password = password[CHUNK_LENGTH:]
-    db.instance_system_metadata_update(context,
-                                       instance_uuid,
-                                       meta,
-                                       False)
+    return meta
 
 
 def handle_password(req, meta_data):
@@ -63,6 +61,12 @@ def handle_password(req, meta_data):
         if (req.content_length > MAX_SIZE or len(req.body) > MAX_SIZE):
             msg = _("Request is too large.")
             raise exc.HTTPBadRequest(explanation=msg)
-        set_password(ctxt, meta_data.uuid, req.body)
+
+        conductor_api = conductor.API()
+        instance = conductor_api.instance_get_by_uuid(ctxt, meta_data.uuid)
+        sys_meta = utils.metadata_to_dict(instance['system_metadata'])
+        sys_meta.update(convert_password(ctxt, req.body))
+        conductor_api.instance_update(ctxt, meta_data.uuid,
+                                      system_metadata=sys_meta)
     else:
         raise exc.HTTPBadRequest()
diff --git a/nova/api/openstack/compute/contrib/server_password.py b/nova/api/openstack/compute/contrib/server_password.py
index 0fd620fb8..9436d354f 100644
--- a/nova/api/openstack/compute/contrib/server_password.py
+++ b/nova/api/openstack/compute/contrib/server_password.py
@@ -24,6 +24,7 @@ from nova.api.openstack import extensions
 from nova.api.openstack import wsgi
 from nova.api.openstack import xmlutil
 from nova import compute
+from nova import db
 from nova import exception
 
 
@@ -62,7 +63,9 @@ class ServerPasswordController(object):
         context = req.environ['nova.context']
         authorize(context)
         instance = self._get_instance(context, server_id)
-        password.set_password(context, instance['uuid'], None)
+        meta = password.convert_password(context, None)
+        db.instance_system_metadata_update(context, instance['uuid'],
+                                           meta, False)
 
 
 class Server_password(extensions.ExtensionDescriptor):