Gracefully handle missing metadata in libvirt xml

Missing metadata in the libvirt domain xml for a nova instance would
cause ceilometer-compute to abort, leading to missing metrics for the
current and any subequent libvirt guests.

This commit puts a try/except AttributeError block around all the code
that is fetching attributes on the result of metadata_xml.find(...).

Change-Id: I8adc609cc21c86de2daba326d24b73a80d6eb61f
Closes-Bug: #1749960

1 files changed, 34 insertions, 22 deletions

diff --git a/ceilometer/compute/discovery.py b/ceilometer/compute/discovery.py
index 47f7369f..fc1698e2 100644
--- a/ceilometer/compute/discovery.py
+++ b/ceilometer/compute/discovery.py
@@ -162,42 +162,54 @@ class InstanceDiscovery(plugin_base.DiscoveryBase):
             # flavor. this is why nova doesn't put the id in the libvirt
             # metadata
 
-            # This implements
-            flavor_xml = metadata_xml.find("./flavor")
-            flavor = {
-                "id": self.get_flavor_id(flavor_xml.attrib["name"]),
-                "name": flavor_xml.attrib["name"],
-                "vcpus": self._safe_find_int(flavor_xml, "vcpus"),
-                "ram": self._safe_find_int(flavor_xml, "memory"),
-                "disk": self._safe_find_int(flavor_xml, "disk"),
-                "ephemeral": self._safe_find_int(flavor_xml, "ephemeral"),
-                "swap": self._safe_find_int(flavor_xml, "swap"),
-            }
+            try:
+                flavor_xml = metadata_xml.find(
+                    "./flavor")
+                user_id = metadata_xml.find(
+                    "./owner/user").attrib["uuid"]
+                project_id = metadata_xml.find(
+                    "./owner/project").attrib["uuid"]
+                instance_name = metadata_xml.find(
+                    "./name").text
+                instance_arch = os_type_xml.attrib["arch"]
+
+                flavor = {
+                    "id": self.get_flavor_id(flavor_xml.attrib["name"]),
+                    "name": flavor_xml.attrib["name"],
+                    "vcpus": self._safe_find_int(flavor_xml, "vcpus"),
+                    "ram": self._safe_find_int(flavor_xml, "memory"),
+                    "disk": self._safe_find_int(flavor_xml, "disk"),
+                    "ephemeral": self._safe_find_int(flavor_xml, "ephemeral"),
+                    "swap": self._safe_find_int(flavor_xml, "swap"),
+                }
+
+                # The image description is partial, but Gnocchi only care about
+                # the id, so we are fine
+                image_xml = metadata_xml.find("./root[@type='image']")
+                image = ({'id': image_xml.attrib['uuid']}
+                         if image_xml is not None else None)
+            except AttributeError as e:
+                LOG.error(
+                    "Fail to get domain uuid %s metadata: "
+                    "metadata was missing expected attributes",
+                    domain.UUIDString())
+
             dom_state = domain.state()[0]
             vm_state = libvirt_utils.LIBVIRT_POWER_STATE.get(dom_state)
             status = libvirt_utils.LIBVIRT_STATUS.get(dom_state)
 
-            user_id = metadata_xml.find("./owner/user").attrib["uuid"]
-            project_id = metadata_xml.find("./owner/project").attrib["uuid"]
-
             # From:
             # https://github.com/openstack/nova/blob/852f40fd0c6e9d8878212ff3120556668023f1c4/nova/api/openstack/compute/views/servers.py#L214-L220
             host_id = hashlib.sha224(
                 (project_id + self.conf.host).encode('utf-8')).hexdigest()
 
-            # The image description is partial, but Gnocchi only care about the
-            # id, so we are fine
-            image_xml = metadata_xml.find("./root[@type='image']")
-            image = ({'id': image_xml.attrib['uuid']}
-                     if image_xml is not None else None)
-
             instance_data = {
                 "id": domain.UUIDString(),
-                "name": metadata_xml.find("./name").text,
+                "name": instance_name,
                 "flavor": flavor,
                 "image": image,
                 "os_type": os_type_xml.text,
-                "architecture": os_type_xml.attrib["arch"],
+                "architecture": instance_arch,
 
                 "OS-EXT-SRV-ATTR:instance_name": domain.name(),
                 "OS-EXT-SRV-ATTR:host": self.conf.host,