common/amqp: fix close() when kombu not initialized

During clean when error happen it may happen that we call close()
where kombu has not yet been initialized from method 'establish()'.

To avoid multiple checks in base-code, the method close() is now doing
no-op is establish has no been initialized.

Closes-Jira-Bug: CEM-19030
Signed-off-by: Sahid Orentino Ferdjaoui <sferdjaoui@juniper.net>
Change-Id: Ic259e47ab93c8c5837d6ebd5f7089d0bde3f5da2

Author: Sahid Orentino Ferdjaoui

src/config/common/cfgm_common/tests/unit/test_amqp.py

@@ -0,0 +1,25 @@
+# -*- coding: utf-8 -*-
+
+#
+# Copyright (c) 2020 Juniper Networks, Inc. All rights reserved.
+#
+
+import unittest
+import mock
+
+from cfgm_common.vnc_amqp import VncAmqpHandle
+
+
+class TestVncAmqp(unittest.TestCase):
+
+    def test_close(self):
+        vnc = VncAmqpHandle(
+            *(7 * [mock.MagicMock()]))
+
+        # Should not raise anything
+        vnc.close()
+
+        # Pretends call of establish()
+        vnc._vnc_kombu = mock.MagicMock()
+        vnc.close()
+        vnc._vnc_kombu.shutdown.assert_called_once_with()

src/config/common/cfgm_common/vnc_amqp.py

@@ -32,6 +32,7 @@ def __init__(self, sandesh, logger, db_cls, reaction_map, q_name_prefix,
         self.timer = timer_obj
         self.host_ip = host_ip
         self.register_handler = register_handler
+        self._vnc_kombu = None
 
     def establish(self):
         q_name = '.'.join([self.q_name_prefix, socket.getfqdn(self.host_ip)])
@@ -262,4 +263,9 @@ def evaluate_dependency(self):
                         self.timer.timed_yield()
 
     def close(self):
-        self._vnc_kombu.shutdown()
+        if self._vnc_kombu is not None:
+            # VncKombuClient is instancied when calling 'establish()',
+            # if for some reasons (mostly related to cleanup after
+            # exception handling) we call `close()` we should consider
+            # a no-op.
+            self._vnc_kombu.shutdown()