Boot from volume without image supplied

This patch allows for booting instances without supplying an image if
there is block device mapping supplied. It makes changes to nova API
and
compute services to handle requests that do not have any image
supplied.

Also it makes rescue and rebuild work with instances started from
volume.

Finally the patch introduces tests to make sure the system acts as
expected, and in the process fixes and refactors some old tests to make
them test for cases this new functionality can introduce.

This patch is intended to be a proof of concept and a first step
towards
a more cleaner interface for booting from volumes, outlined in
https://etherpad.openstack.org/grizzly-boot-from-volumes.

This patch also introduces a slight modification of the nova API so I
am flagging it with DocImpact. The change is that if the os-volumes
extension is used ImageRef does not need to be supplied to the create
server API call provided there is block_device_mapping provided.

Also note that this is the first step towards introducing a 'volume'
parameter
for starting instances which will replace the somewhat unintuitive
block_device_mapping (they will still be used but not for the boot
device).

This patch is coupled with I5ba9b0f35a5084aa91eca260f46cac83b8b6591e
that provides changes to the nova client.

Implements: blueprint improve-boot-from-volume
Fixes bug #1008622

Change-Id: I530760cfaa5eb0cae590c7383e0840c6b3f896b9

2 files changed, 34 insertions, 14 deletions

diff --git a/nova/api/openstack/compute/servers.py b/nova/api/openstack/compute/servers.py
index 9c019f78f..68c5372c3 100644
--- a/nova/api/openstack/compute/servers.py
+++ b/nova/api/openstack/compute/servers.py
@@ -743,8 +743,7 @@ class Controller(wsgi.Controller):
         self._validate_server_name(name)
         name = name.strip()
 
-        image_href = self._image_ref_from_req_data(body)
-        image_href = self._image_uuid_from_href(image_href)
+        image_uuid = self._image_from_req_data(body)
 
         personality = server_dict.get('personality')
         config_drive = None
@@ -855,7 +854,7 @@ class Controller(wsgi.Controller):
 
             (instances, resv_id) = self.compute_api.create(context,
                             inst_type,
-                            image_href,
+                            image_uuid,
                             display_name=name,
                             display_description=name,
                             key_name=key_name,
@@ -1108,6 +1107,24 @@ class Controller(wsgi.Controller):
 
         return image_uuid
 
+    def _image_from_req_data(self, data):
+        """
+        Get image data from the request or raise appropriate
+        exceptions
+
+        If no image is supplied - checks to see if there is
+        block devices set and proper extesions loaded.
+        """
+        image_ref = data['server'].get('imageRef')
+        bdm = data['server'].get('block_device_mapping')
+
+        if not image_ref and bdm and self.ext_mgr.is_loaded('os-volumes'):
+            return ''
+        else:
+            image_href = self._image_ref_from_req_data(data)
+            image_uuid = self._image_uuid_from_href(image_href)
+            return image_uuid
+
     def _flavor_id_from_req_data(self, data):
         try:
             flavor_ref = data['server']['flavorRef']
diff --git a/nova/api/openstack/compute/views/servers.py b/nova/api/openstack/compute/views/servers.py
index b423b37d4..d281f6a61 100644
--- a/nova/api/openstack/compute/views/servers.py
+++ b/nova/api/openstack/compute/views/servers.py
@@ -164,17 +164,20 @@ class ViewBuilder(common.ViewBuilder):
 
     def _get_image(self, request, instance):
         image_ref = instance["image_ref"]
-        image_id = str(common.get_id_from_href(image_ref))
-        bookmark = self._image_builder._get_bookmark_link(request,
-                                                          image_id,
-                                                          "images")
-        return {
-            "id": image_id,
-            "links": [{
-                "rel": "bookmark",
-                "href": bookmark,
-            }],
-        }
+        if image_ref:
+            image_id = str(common.get_id_from_href(image_ref))
+            bookmark = self._image_builder._get_bookmark_link(request,
+                                                              image_id,
+                                                              "images")
+            return {
+                "id": image_id,
+                "links": [{
+                    "rel": "bookmark",
+                    "href": bookmark,
+                }],
+            }
+        else:
+            return ""
 
     def _get_flavor(self, request, instance):
         instance_type = instance["instance_type"]