Add request id to returned objects

Adding two classes RequestIdProxy and GeneratorProxy derived from
wrapt.ObjectProxy to wrap objects returned from the API.

GeneratorProxy class is used to wrap generator objects returned
by cases like images.list() etc. whereas RequestIdProxy class is
used to wrap non-generator object cases like images.create() etc.

In all cases the returned object will have the same behavior as
the wrapped(original) object. However now the returned objects
will have an extra property 'request_ids' which is a list of
exactly one request id.

For generator cases the request_ids property will be an empty list
until the underlying generator is invoked at-least once.

Co-Authored-By: Abhishek Kekane <abhishek.kekane@nttdata.com>

Closes-Bug: #1525259
Blueprint: return-request-id-to-caller
Change-Id: If8c0e0843270ff718a37ca2697afeb8da22aa3b1

glanceclient/tests/unit/test_utils.py

@@ -17,6 +17,7 @@ import sys
 
 import mock
 from oslo_utils import encodeutils
+from requests import Response
 import six
 # NOTE(jokke): simplified transition to py3, behaves like py2 xrange
 from six.moves import range
@@ -25,6 +26,15 @@ import testtools
 from glanceclient.common import utils
 
 
+REQUEST_ID = 'req-1234'
+
+
+def create_response_obj_with_req_id(req_id):
+    resp = Response()
+    resp.headers['x-openstack-request-id'] = req_id
+    return resp
+
+
 class TestUtils(testtools.TestCase):
 
     def test_make_size_human_readable(self):
@@ -178,3 +188,43 @@ class TestUtils(testtools.TestCase):
             (name, value) = utils.safe_header(sensitive_header, None)
             self.assertEqual(sensitive_header, name)
             self.assertIsNone(value)
+
+    def test_generator_proxy(self):
+        def _test_decorator():
+            i = 1
+            resp = create_response_obj_with_req_id(REQUEST_ID)
+            while True:
+                yield i, resp
+                i += 1
+
+        gen_obj = _test_decorator()
+        proxy = utils.GeneratorProxy(gen_obj)
+
+        # Proxy object should succeed in behaving as the
+        # wrapped object
+        self.assertTrue(isinstance(proxy, type(gen_obj)))
+
+        # Initially request_ids should be empty
+        self.assertEqual([], proxy.request_ids)
+
+        # Only after we have started iterating we should
+        # see non-empty `request_ids` property
+        proxy.next()
+        self.assertEqual([REQUEST_ID], proxy.request_ids)
+
+        # Even after multiple iterations `request_ids` property
+        # should only contain one request id
+        proxy.next()
+        proxy.next()
+        self.assertEqual(1, len(proxy.request_ids))
+
+    def test_request_id_proxy(self):
+        def test_data(val):
+            resp = create_response_obj_with_req_id(REQUEST_ID)
+            return val, resp
+
+        # Object of any type except decorator can be passed to test_data
+        proxy = utils.RequestIdProxy(test_data(11))
+        # Verify that proxy object has a property `request_ids` and it is
+        # a list of one request id
+        self.assertEqual([REQUEST_ID], proxy.request_ids)