Fix CPU duration reporting

CPU usage was not properly reported, since we only got the CPU time from
cASO's last run. We should get it from the start of the server instead.

Closes #26

Author: alvarolopez

caso/extract/nova.py

@@ -15,6 +15,7 @@
 # under the License.
 
 import datetime
+import operator
 
 import dateutil.parser
 from dateutil import tz
@@ -69,8 +70,15 @@ def extract_for_tenant(self, tenant, lastrun):
         tenant_id = conn.client.tenant_id
         servers = conn.servers.list(search_opts={"changes-since": lastrun})
 
-        # FIXME(aloga): use start and end from the retreived servers
-        aux = conn.usage.get(tenant_id, lastrun, end)
+        servers = sorted(servers, key=operator.attrgetter("created"))
+
+        if servers:
+            start = dateutil.parser.parse(servers[0].created)
+            start.replace(tzinfo=None)
+        else:
+            start = lastrun
+
+        aux = conn.usage.get(tenant_id, start, end)
         usages = getattr(aux, "server_usages", [])
 
         images = conn.images.list()
@@ -109,7 +117,6 @@ def extract_for_tenant(self, tenant, lastrun):
             records[instance_id].memory = usage["memory_mb"]
             records[instance_id].cpu_count = usage["vcpus"]
             records[instance_id].disk = usage["local_gb"]
-            records[instance_id].cpu_duration = int(usage["hours"] * 3600)
 
             started = dateutil.parser.parse(usage["started_at"])
             records[instance_id].start_time = int(started.strftime("%s"))
@@ -120,5 +127,11 @@ def extract_for_tenant(self, tenant, lastrun):
             else:
                 wall = now - started
 
-            records[instance_id].wall_duration = int(wall.total_seconds())
+            wall = int(wall.total_seconds())
+            records[instance_id].wall_duration = wall
+
+            cput = int(usage["hours"] * 3600)
+            # NOTE(aloga): in some cases there may be rounding errors and cput
+            # may be larger than wall.
+            records[instance_id].cpu_duration = cput if cput < wall else wall
         return records