save_and_reraise_exception: make logging respect the reraise parameter

Do not log original exception if reraise is set to False

Closes-Bug: #1291850
Related-Bug: #1288188

Change-Id: Icd5fcba25c2cd549cee70353a7a62d83bfe1255b

openstack/common/excutils.py

@@ -49,9 +49,22 @@ class save_and_reraise_exception(object):
               decide_if_need_reraise()
               if not should_be_reraised:
                   ctxt.reraise = False
+
+    If another exception occurs and reraise flag is False,
+    the saved exception will not be logged.
+
+    If the caller wants to raise new exception during exception handling
+    he/she sets reraise to False initially with an ability to set it back to
+    True if needed::
+
+      except Exception:
+          with save_and_reraise_exception(reraise=False) as ctxt:
+              [if statements to determine whether to raise a new exception]
+              # Not raising a new exception, so reraise
+              ctxt.reraise = True
     """
-    def __init__(self):
+    def __init__(self, reraise=True):
-        self.reraise = True
+        self.reraise = reraise
 
     def __enter__(self):
         self.type_, self.value, self.tb, = sys.exc_info()
@@ -59,10 +72,11 @@ class save_and_reraise_exception(object):
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         if exc_type is not None:
-            logging.error(_LE('Original exception being dropped: %s'),
+            if self.reraise:
-                          traceback.format_exception(self.type_,
+                logging.error(_LE('Original exception being dropped: %s'),
-                                                     self.value,
+                              traceback.format_exception(self.type_,
-                                                     self.tb))
+                                                         self.value,
+                                                         self.tb))
             return False
         if self.reraise:
             six.reraise(self.type_, self.value, self.tb)

tests/unit/test_excutils.py

@@ -15,6 +15,8 @@
 import logging
 import time
 
+import mock
+
 from openstack.common import excutils
 from openstack.common.fixture import moxstubout
 from openstack.common import test
@@ -42,16 +44,18 @@ class SaveAndReraiseTest(test.BaseTestCase):
     def test_save_and_reraise_exception_dropped(self):
         e = None
         msg = 'second exception'
-        try:
+        with mock.patch('logging.error') as log:
             try:
-                raise Exception('dropped')
+                try:
-            except Exception:
+                    raise Exception('dropped')
-                with excutils.save_and_reraise_exception():
+                except Exception:
-                    raise Exception(msg)
+                    with excutils.save_and_reraise_exception():
-        except Exception as _e:
+                        raise Exception(msg)
-            e = _e
+            except Exception as _e:
+                e = _e
 
-        self.assertEqual(str(e), msg)
+            self.assertEqual(str(e), msg)
+            self.assertTrue(log.called)
 
     def test_save_and_reraise_exception_no_reraise(self):
         """Test that suppressing the reraise works."""
@@ -61,6 +65,22 @@ class SaveAndReraiseTest(test.BaseTestCase):
             with excutils.save_and_reraise_exception() as ctxt:
                 ctxt.reraise = False
 
+    def test_save_and_reraise_exception_dropped_no_reraise(self):
+        e = None
+        msg = 'second exception'
+        with mock.patch('logging.error') as log:
+            try:
+                try:
+                    raise Exception('dropped')
+                except Exception:
+                    with excutils.save_and_reraise_exception(reraise=False):
+                        raise Exception(msg)
+            except Exception as _e:
+                e = _e
+
+            self.assertEqual(str(e), msg)
+            self.assertFalse(log.called)
+
 
 class ForeverRetryUncaughtExceptionsTest(test.BaseTestCase):