Allow providing a logger to save_and_reraise_exception

Instead of always assuming the best logger to use when
a exception is being dropped is the root logger (which
it may not always be) allow for providing a custom
logger when using this functionality + class so that
users can direct it to a logger of there choosing.

Change-Id: Ic56892be9d007229f5c302a2c6da19f00e91752e

3 files changed, 70 insertions, 53 deletions

diff --git a/oslo_utils/excutils.py b/oslo_utils/excutils.py
index c5839d6..4e4c669 100644
--- a/oslo_utils/excutils.py
+++ b/oslo_utils/excutils.py
@@ -63,8 +63,11 @@ class save_and_reraise_exception(object):
               # Not raising a new exception, so reraise
               ctxt.reraise = True
     """
-    def __init__(self, reraise=True):
+    def __init__(self, reraise=True, logger=None):
         self.reraise = reraise
+        if logger is None:
+            logger = logging.getLogger()
+        self.logger = logger
 
     def __enter__(self):
         self.type_, self.value, self.tb, = sys.exc_info()
@@ -73,10 +76,10 @@ class save_and_reraise_exception(object):
     def __exit__(self, exc_type, exc_val, exc_tb):
         if exc_type is not None:
             if self.reraise:
-                logging.error(_LE('Original exception being dropped: %s'),
-                              traceback.format_exception(self.type_,
-                                                         self.value,
-                                                         self.tb))
+                self.logger.error(_LE('Original exception being dropped: %s'),
+                                  traceback.format_exception(self.type_,
+                                                             self.value,
+                                                             self.tb))
             return False
         if self.reraise:
             six.reraise(self.type_, self.value, self.tb)
diff --git a/oslo_utils/tests/test_excutils.py b/oslo_utils/tests/test_excutils.py
index 92bf39c..c2626a4 100644
--- a/oslo_utils/tests/test_excutils.py
+++ b/oslo_utils/tests/test_excutils.py
@@ -41,21 +41,21 @@ class SaveAndReraiseTest(test_base.BaseTestCase):
 
         self.assertEqual(str(e), msg)
 
-    def test_save_and_reraise_exception_dropped(self):
+    @mock.patch('logging.getLogger')
+    def test_save_and_reraise_exception_dropped(self, get_logger_mock):
+        logger = get_logger_mock()
         e = None
         msg = 'second exception'
-        with mock.patch('logging.error') as log:
+        try:
             try:
-                try:
-                    raise Exception('dropped')
-                except Exception:
-                    with excutils.save_and_reraise_exception():
-                        raise Exception(msg)
-            except Exception as _e:
-                e = _e
-
-            self.assertEqual(str(e), msg)
-            self.assertTrue(log.called)
+                raise Exception('dropped')
+            except Exception:
+                with excutils.save_and_reraise_exception():
+                    raise Exception(msg)
+        except Exception as _e:
+            e = _e
+        self.assertEqual(str(e), msg)
+        self.assertTrue(logger.error.called)
 
     def test_save_and_reraise_exception_no_reraise(self):
         """Test that suppressing the reraise works."""
@@ -65,21 +65,34 @@ class SaveAndReraiseTest(test_base.BaseTestCase):
             with excutils.save_and_reraise_exception() as ctxt:
                 ctxt.reraise = False
 
-    def test_save_and_reraise_exception_dropped_no_reraise(self):
+    @mock.patch('logging.getLogger')
+    def test_save_and_reraise_exception_dropped_no_reraise(self,
+                                                           get_logger_mock):
+        logger = get_logger_mock()
         e = None
         msg = 'second exception'
-        with mock.patch('logging.error') as log:
+        try:
             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)
+                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(logger.error.called)
+
+    def test_save_and_reraise_exception_provided_logger(self):
+        fake_logger = mock.MagicMock()
+        try:
+            try:
+                raise Exception('foo')
+            except Exception:
+                with excutils.save_and_reraise_exception(logger=fake_logger):
+                    raise Exception('second exception')
+        except Exception:
+            pass
+        self.assertTrue(fake_logger.error.called)
 
 
 class ForeverRetryUncaughtExceptionsTest(test_base.BaseTestCase):
diff --git a/tests/test_excutils.py b/tests/test_excutils.py
index 2ccac55..3f35e79 100644
--- a/tests/test_excutils.py
+++ b/tests/test_excutils.py
@@ -41,21 +41,21 @@ class SaveAndReraiseTest(test_base.BaseTestCase):
 
         self.assertEqual(str(e), msg)
 
-    def test_save_and_reraise_exception_dropped(self):
+    @mock.patch('logging.getLogger')
+    def test_save_and_reraise_exception_dropped(self, get_logger_mock):
+        logger = get_logger_mock()
         e = None
         msg = 'second exception'
-        with mock.patch('logging.error') as log:
+        try:
             try:
-                try:
-                    raise Exception('dropped')
-                except Exception:
-                    with excutils.save_and_reraise_exception():
-                        raise Exception(msg)
-            except Exception as _e:
-                e = _e
-
-            self.assertEqual(str(e), msg)
-            self.assertTrue(log.called)
+                raise Exception('dropped')
+            except Exception:
+                with excutils.save_and_reraise_exception():
+                    raise Exception(msg)
+        except Exception as _e:
+            e = _e
+        self.assertEqual(str(e), msg)
+        self.assertTrue(logger.error.called)
 
     def test_save_and_reraise_exception_no_reraise(self):
         """Test that suppressing the reraise works."""
@@ -65,21 +65,22 @@ class SaveAndReraiseTest(test_base.BaseTestCase):
             with excutils.save_and_reraise_exception() as ctxt:
                 ctxt.reraise = False
 
-    def test_save_and_reraise_exception_dropped_no_reraise(self):
+    @mock.patch('logging.getLogger')
+    def test_save_and_reraise_exception_dropped_no_reraise(self,
+                                                           get_logger_mock):
+        logger = get_logger_mock()
         e = None
         msg = 'second exception'
-        with mock.patch('logging.error') as log:
+        try:
             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)
+                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(logger.error.called)
 
 
 class ForeverRetryUncaughtExceptionsTest(test_base.BaseTestCase):