Fix uses of service_get_all_compute_by_host

There should never be more than 1 service entry for the same topic and
host, however this method returns a list of services.  All callers of
this method except for 1 already account for there being only 1 service
entry for a particular 'compute' host and only use the first entry in the
return list.

This patch renames the DB API call to be 'service_get_by_compute_host'
and returns a single entry.  All uses of the old method are adjusted
accordingly.

Change-Id: I0e0ef62f5d2e71efe756940d9fdd98aa02fef216

3 files changed, 12 insertions, 19 deletions

diff --git a/nova/compute/api.py b/nova/compute/api.py
index d0a039644..1ad9e2aee 100644
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -954,19 +954,16 @@ class API(base.Base):
                             host=src_host, cast=False,
                             reservations=downsize_reservations)
 
-            # NOTE(jogo): db allows for multiple compute services per host
+            is_up = False
             try:
-                services = self.db.service_get_all_compute_by_host(
+                service = self.db.service_get_by_compute_host(
                         context.elevated(), instance['host'])
-            except exception.ComputeHostNotFound:
-                services = []
-
-            is_up = False
-            for service in services:
                 if self.servicegroup_api.service_is_up(service):
                     is_up = True
                     cb(context, instance, bdms)
-                    break
+            except exception.ComputeHostNotFound:
+                pass
+
             if not is_up:
                 # If compute node isn't up, just delete from DB
                 self._local_delete(context, instance, bdms)
@@ -2238,9 +2235,8 @@ class HostAPI(base.Base):
         """
         # Getting compute node info and related instances info
         try:
-            compute_ref = self.db.service_get_all_compute_by_host(context,
-                host_name)
-            compute_ref = compute_ref[0]
+            compute_ref = self.db.service_get_by_compute_host(context,
+                                                              host_name)
         except exception.ComputeHostNotFound:
             raise exception.HostNotFound(host=host_name)
         instance_refs = self.db.instance_get_all_by_host(context,
@@ -2360,8 +2356,7 @@ class AggregateAPI(base.Base):
     def add_host_to_aggregate(self, context, aggregate_id, host_name):
         """Adds the host to an aggregate."""
         # validates the host; ComputeHostNotFound is raised if invalid
-        service = self.db.service_get_all_compute_by_host(
-                context, host_name)[0]
+        self.db.service_get_by_compute_host(context, host_name)
         aggregate = self.db.aggregate_get(context, aggregate_id)
         self.db.aggregate_host_add(context, aggregate_id, host_name)
         #NOTE(jogo): Send message to host to support resource pools
@@ -2372,8 +2367,7 @@ class AggregateAPI(base.Base):
     def remove_host_from_aggregate(self, context, aggregate_id, host_name):
         """Removes host from the aggregate."""
         # validates the host; ComputeHostNotFound is raised if invalid
-        service = self.db.service_get_all_compute_by_host(
-                context, host_name)[0]
+        self.db.service_get_by_compute_host(context, host_name)
         aggregate = self.db.aggregate_get(context, aggregate_id)
         self.db.aggregate_host_delete(context, aggregate_id, host_name)
         self.compute_rpcapi.remove_aggregate_host(context,
diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 85942541f..d8021ac7d 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -2592,10 +2592,10 @@ class ComputeManager(manager.SchedulerDependentManager):
             pass
 
     def _get_compute_info(self, context, host):
-        compute_node_ref = self.conductor_api.service_get_all_compute_by_host(
+        compute_node_ref = self.conductor_api.service_get_by_compute_host(
             context, host)
         try:
-            return compute_node_ref[0]['compute_node'][0]
+            return compute_node_ref['compute_node'][0]
         except IndexError:
             raise exception.NotFound(_("Host %(host)s not found") % locals())
 
diff --git a/nova/compute/resource_tracker.py b/nova/compute/resource_tracker.py
index 075d59ec8..d2afcaa27 100644
--- a/nova/compute/resource_tracker.py
+++ b/nova/compute/resource_tracker.py
@@ -308,8 +308,7 @@ class ResourceTracker(object):
 
     def _get_service(self, context):
         try:
-            return db.service_get_all_compute_by_host(context,
-                    self.host)[0]
+            return db.service_get_by_compute_host(context, self.host)
         except exception.NotFound:
             LOG.warn(_("No service record for host %s"), self.host)