Fix issues with re-raising exceptions.

There is complication with re-raising exceptions and our usage of
eventlet.  If the code in the exception handler accesses the db or rpc
in the exception handler, it will no longer be able to re-raise the
exception.  Using excutils.save_and_reraise_exception() works aorund
this issue.

The most common error is calling LOG.error() or LOG.exception(), as it
is possible for these to go access rpc.  There is an option to turn on
notifications for these errors.

Fix bug 845866.

Change-Id: Icfca2af63805711229249aa7abe60a938edd1b35

nova/notifications.py

@@ -26,6 +26,7 @@ from nova import db
 from nova.image import glance
 from nova import network
 from nova.network import model as network_model
+from nova.openstack.common import excutils
 from nova.openstack.common import log
 from nova.openstack.common.notifier import api as notifier_api
 from nova.openstack.common import timeutils
@@ -225,10 +226,14 @@ def bandwidth_usage(instance_ref, audit_start,
             nw_info = network.API().get_instance_nw_info(admin_context,
                     instance_ref)
         except Exception:
-            LOG.exception(_('Failed to get nw_info'), instance=instance_ref)
-            if ignore_missing_network_data:
-                return
-            raise
+            try:
+                with excutils.save_and_reraise_exception():
+                    LOG.exception(_('Failed to get nw_info'),
+                                  instance=instance_ref)
+            except Exception:
+                if ignore_missing_network_data:
+                    return
+                raise
 
     macs = [vif['address'] for vif in nw_info]
     uuids = [instance_ref["uuid"]]

nova/scheduler/scheduler_options.py

@@ -28,6 +28,7 @@ import os
 
 from oslo.config import cfg
 
+from nova.openstack.common import excutils
 from nova.openstack.common import log as logging
 from nova.openstack.common import timeutils
 
@@ -66,9 +67,9 @@ class SchedulerOptions(object):
         try:
             return os.path.getmtime(filename)
         except os.error, e:
-            LOG.exception(_("Could not stat scheduler options file "
-                            "%(filename)s: '%(e)s'"), locals())
-            raise
+            with excutils.save_and_reraise_exception():
+                LOG.exception(_("Could not stat scheduler options file "
+                                "%(filename)s: '%(e)s'"), locals())
 
     def _load_file(self, handle):
         """Decode the JSON file. Broken out for testing."""

nova/wsgi.py

@@ -34,6 +34,7 @@ import webob.dec
 import webob.exc
 
 from nova import exception
+from nova.openstack.common import excutils
 from nova.openstack.common import log as logging
 
 wsgi_opts = [
@@ -175,9 +176,9 @@ class Server(object):
                                     CONF.tcp_keepidle)
 
             except Exception:
-                LOG.error(_("Failed to start %(name)s on %(host)s"
-                            ":%(port)s with SSL support") % self.__dict__)
-                raise
+                with excutils.save_and_reraise_exception():
+                    LOG.error(_("Failed to start %(name)s on %(host)s"
+                                ":%(port)s with SSL support") % self.__dict__)
 
         wsgi_kwargs = {
             'func': eventlet.wsgi.server,