Fix handling of "Permission Denied" error from NamedTemporaryFile function

If "Permission Denied" has happen in NamedTemporaryFile function in
dump_recon_cache method, swift will log a message of reference to a variable
without assignment and not log a message of "Permission Denied".
This patch fixes the handling and add an unit test.

Co-Authored-By: Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp>
Change-Id: Iafdd94905e9e9c81f5966a923324b50c18fcf592

swift/common/utils.py

@@ -2566,17 +2566,19 @@ def dump_recon_cache(cache_dict, cache_file, logger, lock_timeout=2):
                 pass
             for cache_key, cache_value in cache_dict.items():
                 put_recon_cache_entry(cache_entry, cache_key, cache_value)
+            tf = None
             try:
                 with NamedTemporaryFile(dir=os.path.dirname(cache_file),
                                         delete=False) as tf:
                     tf.write(json.dumps(cache_entry) + '\n')
                 renamer(tf.name, cache_file, fsync=False)
             finally:
-                try:
-                    os.unlink(tf.name)
-                except OSError as err:
-                    if err.errno != errno.ENOENT:
-                        raise
+                if tf is not None:
+                    try:
+                        os.unlink(tf.name)
+                    except OSError as err:
+                        if err.errno != errno.ENOENT:
+                            raise
     except (Exception, Timeout):
         logger.exception(_('Exception dumping recon cache'))
 

test/unit/common/test_utils.py

@@ -1216,6 +1216,29 @@ class TestUtils(unittest.TestCase):
         finally:
             rmtree(testdir_base)
 
+    def test_dump_recon_cache_permission_denied(self):
+        testdir_base = mkdtemp()
+        testcache_file = os.path.join(testdir_base, 'cache.recon')
+
+        class MockLogger(object):
+            def __init__(self):
+                self._excs = []
+
+            def exception(self, message):
+                _junk, exc, _junk = sys.exc_info()
+                self._excs.append(exc)
+
+        logger = MockLogger()
+        try:
+            submit_dict = {'key1': {'value1': 1, 'value2': 2}}
+            with mock.patch(
+                    'swift.common.utils.NamedTemporaryFile',
+                    side_effect=IOError(13, 'Permission Denied')):
+                utils.dump_recon_cache(submit_dict, testcache_file, logger)
+            self.assertIsInstance(logger._excs[0], IOError)
+        finally:
+            rmtree(testdir_base)
+
     def test_get_logger(self):
         sio = StringIO()
         logger = logging.getLogger('server')