Add a Python context that logs exceptions

The Python context named `ExceptionLogger` can be used to
route exceptions to a specified logging service.

Change-Id: I85d74339ac8857e7d577302d29c5951b76a1d127

rally/benchmark/context/flavors.py

@@ -98,14 +98,10 @@ class FlavorsGenerator(base.Context):
         """Delete created flavors."""
         clients = osclients.Clients(self.context["admin"]["endpoint"])
         for flavor in self.context["flavors"].values():
-            try:
+            with logging.ExceptionLogger(
+                    LOG, _("Can't delete flavor %s") % flavor["id"]):
                 rutils.retry(3, clients.nova().flavors.delete, flavor["id"])
                 LOG.debug("Flavor is deleted %s" % flavor["id"])
-            except Exception as e:
-                LOG.error(
-                    "Can't delete flavor %s: %s" % (flavor["id"], e.message))
-                if logging.is_debug():
-                    LOG.exception(e)
 
 
 class FlavorConfig(dict):

rally/benchmark/context/network.py

@@ -71,8 +71,8 @@ class Network(base.Context):
     def cleanup(self):
         for tenant_id, tenant_ctx in six.iteritems(self.context["tenants"]):
             for network in tenant_ctx.get("networks", []):
-                try:
+                with logging.ExceptionLogger(
+                        LOG,
+                        _("Failed to delete network for tenant %s")
+                        % tenant_id):
                     self.net_wrapper.delete_network(network)
-                except Exception as e:
-                    LOG.error("Failed to delete network for tenant %s\n"
-                              " reason: %s" % (tenant_id, e))

rally/benchmark/context/roles.py

@@ -74,13 +74,10 @@ class RoleGenerator(base.Context):
         client = osclients.Clients(admin_endpoint).keystone()
 
         for user in self.context["users"]:
-            try:
+            with logging.ExceptionLogger(
+                    LOG, _("Failed to remove role: %s") % role["id"]):
                 client.roles.remove_user_role(
                     user["id"], role["id"], tenant=user["tenant_id"])
-            except Exception as ex:
-                LOG.warning("Failed to remove role: %(role_id)s. "
-                            "Exception: %(ex)s" %
-                            {"role_id": role["id"], "ex": ex})
 
     @rutils.log_task_wrapper(LOG.info, _("Enter context: `roles`"))
     def setup(self):

rally/benchmark/context/secgroup.py

@@ -108,9 +108,6 @@ class AllowSSH(base.Context):
     @utils.log_task_wrapper(LOG.info, _("Exit context: `allow_ssh`"))
     def cleanup(self):
         for secgroup in self.secgroup:
-            try:
+            with logging.ExceptionLogger(
+                    LOG, _("Unable to delete secgroup: %s.") % secgroup.id):
                 secgroup.delete()
-            except Exception as ex:
-                LOG.warning("Unable to delete secgroup: %(group_id)s. "
-                            "Exception: %(ex)s" %
-                            {"group_id": secgroup.id, "ex": ex})

rally/common/log.py

@@ -67,5 +67,40 @@ class RallyContextAdapter(oslogging.ContextAdapter):
         self.log(logging.RDEBUG, msg, *args, **kwargs)
 
 
+class ExceptionLogger(object):
+    """Context that intercepts and logs exceptions.
+
+    Usage::
+        LOG = logging.getLogger(__name__)
+        ...
+
+        def foobar():
+            with ExceptionLogger(LOG, "foobar warning") as e:
+                return house_of_raising_exception()
+
+            if e.exception:
+                raise e.exception # remove if not required
+    """
+
+    def __init__(self, logger, warn=None):
+        self.logger = logger
+        self.warn = warn
+        self.exception = None
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type_, value, traceback):
+        if value:
+            self.exception = value
+
+            if self.warn:
+                self.logger.warning(self.warn)
+            self.logger.debug(value)
+            if is_debug():
+                self.logger.exception(value)
+            return True
+
+
 def is_debug():
     return CONF.debug or CONF.rally_debug

tests/unit/test_log.py

@@ -76,3 +76,27 @@ class LogRallyContaxtAdapter(test.TestCase):
 
         radapter.log.assert_called_once_with(mock_logging.RDEBUG,
                                              fake_msg)
+
+
+class ExceptionLoggerTestCase(test.TestCase):
+
+    @mock.patch("rally.common.log.is_debug")
+    def test_context(self, mock_is_debug):
+        # Prepare
+        mock_is_debug.return_value = True
+
+        logger = mock.MagicMock()
+        exception = Exception()
+
+        # Run
+        with log.ExceptionLogger(logger, "foo") as e:
+            raise exception
+
+        # Assertions
+        logger.warning.assert_called_once_with("foo")
+
+        logger.exception.assert_called_once_with(exception)
+
+        logger.debug.assert_called_once_with(exception)
+
+        self.assertEqual(e.exception, exception)