Handle waiting for conductor in nova.service.

Previously we were waiting for conductor to respond to a ping() in the
compute manager.  This patch moves this down to the base Service class.
A nova service binary can indicate that db access is not allowed and if
so, as soon as the service gets created, it will block while waiting for
conductor to respond.

The compute service has been updated to use this.  This should not
result in any real functional difference.

The reason for this is that there is some database access that needs to
be avoided down at this level.  This allows us to divert these actions
to conductor if needed.

Part of bp no-db-compute.

Change-Id: Idd6387b9428e3f9f4e4dbfe51293693238b2daf0

3 files changed, 16 insertions, 12 deletions

diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 98ed1286e..a517f8ffb 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -478,15 +478,12 @@ class ComputeManager(manager.SchedulerDependentManager):
                 LOG.warning(_('Hypervisor driver does not support '
                               'firewall rules'), instance=instance)
 
-    def _get_instances_at_startup(self, context):
-        self.conductor_api.wait_until_ready(context)
-        return self.conductor_api.instance_get_all_by_host(context, self.host)
-
     def init_host(self):
         """Initialization for a standalone compute service."""
         self.driver.init_host(host=self.host)
         context = nova.context.get_admin_context()
-        instances = self._get_instances_at_startup(context)
+        instances = self.conductor_api.instance_get_all_by_host(context,
+                                                                self.host)
 
         if CONF.defer_iptables_apply:
             self.driver.filter_defer_apply_on()
diff --git a/nova/service.py b/nova/service.py
index 86f022f61..05049d464 100644
--- a/nova/service.py
+++ b/nova/service.py
@@ -30,6 +30,7 @@ import time
 import eventlet
 import greenlet
 
+from nova import conductor
 from nova import context
 from nova import db
 from nova import exception
@@ -38,6 +39,7 @@ from nova.openstack.common import eventlet_backdoor
 from nova.openstack.common import importutils
 from nova.openstack.common import log as logging
 from nova.openstack.common import rpc
+from nova.openstack.common.rpc import common as rpc_common
 from nova import servicegroup
 from nova import utils
 from nova import version
@@ -392,7 +394,7 @@ class Service(object):
 
     def __init__(self, host, binary, topic, manager, report_interval=None,
                  periodic_enable=None, periodic_fuzzy_delay=None,
-                 periodic_interval_max=None,
+                 periodic_interval_max=None, db_allowed=True,
                  *args, **kwargs):
         self.host = host
         self.binary = binary
@@ -407,6 +409,9 @@ class Service(object):
         self.saved_args, self.saved_kwargs = args, kwargs
         self.timers = []
         self.backdoor_port = None
+        self.db_allowed = db_allowed
+        self.conductor_api = conductor.API(use_local=db_allowed)
+        self.conductor_api.wait_until_ready(context.get_admin_context())
         self.servicegroup_api = servicegroup.API()
 
     def start(self):
@@ -481,7 +486,8 @@ class Service(object):
     @classmethod
     def create(cls, host=None, binary=None, topic=None, manager=None,
                report_interval=None, periodic_enable=None,
-               periodic_fuzzy_delay=None, periodic_interval_max=None):
+               periodic_fuzzy_delay=None, periodic_interval_max=None,
+               db_allowed=True):
         """Instantiates class and passes back application object.
 
         :param host: defaults to CONF.host
@@ -514,7 +520,8 @@ class Service(object):
                           report_interval=report_interval,
                           periodic_enable=periodic_enable,
                           periodic_fuzzy_delay=periodic_fuzzy_delay,
-                          periodic_interval_max=periodic_interval_max)
+                          periodic_interval_max=periodic_interval_max,
+                          db_allowed=db_allowed)
 
         return service_obj
 
diff --git a/nova/tests/compute/test_compute.py b/nova/tests/compute/test_compute.py
index 23df703be..2239e243a 100644
--- a/nova/tests/compute/test_compute.py
+++ b/nova/tests/compute/test_compute.py
@@ -3175,8 +3175,8 @@ class ComputeTestCase(BaseTestCase):
         def _do_mock_calls(defer_iptables_apply):
             self.compute.driver.init_host(host=our_host)
             context.get_admin_context().AndReturn(fake_context)
-            self.compute._get_instances_at_startup(fake_context).AndReturn(
-                    startup_instances)
+            self.compute.conductor_api.instance_get_all_by_host(
+                    fake_context, our_host).AndReturn(startup_instances)
             if defer_iptables_apply:
                 self.compute.driver.filter_defer_apply_on()
             self.compute._destroy_evacuated_instances(fake_context)
@@ -3193,8 +3193,8 @@ class ComputeTestCase(BaseTestCase):
                                  'filter_defer_apply_on')
         self.mox.StubOutWithMock(self.compute.driver,
                 'filter_defer_apply_off')
-        self.mox.StubOutWithMock(self.compute,
-                                 '_get_instances_at_startup')
+        self.mox.StubOutWithMock(self.compute.conductor_api,
+                                 'instance_get_all_by_host')
         self.mox.StubOutWithMock(context, 'get_admin_context')
         self.mox.StubOutWithMock(self.compute,
                 '_destroy_evacuated_instances')