Fix UnixDomainHttpProtocol class to support all eventlet versions

It was recently decided to uncap eventlet:
http://lists.openstack.org/pipermail/openstack-dev/2018-April/129096.html
So eventlet is now capped at 0.20 not by global requirements,
it is capped in upper-constraints, because currently not every
openstack project is able to work with a newer eventlet version,
mostly because of the caps in projects requirements.txt.
According to global-requirements, last allowed version of
eventlet is 0.22.1:
https://git.openstack.org/cgit/openstack/requirements/tree/global-requirements.txt

In an effort to support both eventlet<0.22 and eventlet>=0.22,
change the code to try and determine the correct number of
arguments to use in the call to initialize the parent class.

Change-Id: Ibe3dc8af6cf9f8bb4f8eababb7f4276e4db3f1f9
Closes-bug: #1777640

neutron/agent/linux/utils.py

@@ -387,24 +387,32 @@ class UnixDomainHTTPConnection(httplib.HTTPConnection):
 
 
 class UnixDomainHttpProtocol(eventlet.wsgi.HttpProtocol):
-    def __init__(self, request, client_address, server):
-        if not client_address:
-            client_address = ('<local>', 0)
-
+    def __init__(self, *args):
         # NOTE(yamahata): from eventlet v0.22 HttpProtocol.__init__
         # signature was changed by changeset of
         # 7f53465578543156e7251e243c0636e087a8445f
-        # try the new signature first, and then fallback to the old
-        # signature for compatibility
-        try:
-            conn_state = [client_address, request, eventlet.wsgi.STATE_CLOSE]
+        # Both have server as last arg, but first arg(s) differ
+        server = args[-1]
+
+        # Because the caller is eventlet.wsgi.Server.process_request,
+        # the number of arguments will dictate if it is new or old style.
+        if len(args) == 2:
+            conn_state = args[0]
+            client_address = conn_state[0]
+            if not client_address:
+                conn_state[0] = ('<local>', 0)
             # base class is old-style, so super does not work properly
             eventlet.wsgi.HttpProtocol.__init__(self, conn_state, server)
-        except (AttributeError, TypeError):
-            # AttributeError: missing STATE_CLOSE
-            # TypeError: signature mismatch
+        elif len(args) == 3:
+            request = args[0]
+            client_address = args[1]
+            if not client_address:
+                client_address = ('<local>', 0)
+            # base class is old-style, so super does not work properly
             eventlet.wsgi.HttpProtocol.__init__(
                 self, request, client_address, server)
+        else:
+            eventlet.wsgi.HttpProtocol.__init__(self, *args)
 
 
 class UnixDomainWSGIServer(wsgi.Server):

neutron/tests/unit/agent/linux/test_utils.py

@@ -12,6 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
 import signal
 import socket
 
@@ -483,14 +484,37 @@ class TestUnixDomainHttpConnection(base.BaseTestCase):
 
 
 class TestUnixDomainHttpProtocol(base.BaseTestCase):
+    def setUp(self):
+        super(TestUnixDomainHttpProtocol, self).setUp()
+        self.ewhi = mock.patch('eventlet.wsgi.HttpProtocol.__init__').start()
+
     def test_init_empty_client(self):
         for addr in ('', b''):
-            u = utils.UnixDomainHttpProtocol(mock.Mock(), addr, mock.Mock())
-            self.assertEqual(u.client_address, ('<local>', 0))
+            utils.UnixDomainHttpProtocol(mock.Mock(), addr, mock.Mock())
+            self.ewhi.assert_called_once_with(mock.ANY, mock.ANY,
+                                              ('<local>', 0), mock.ANY)
+            self.ewhi.reset_mock()
 
     def test_init_with_client(self):
-        u = utils.UnixDomainHttpProtocol(mock.Mock(), 'foo', mock.Mock())
-        self.assertEqual(u.client_address, 'foo')
+        utils.UnixDomainHttpProtocol(mock.Mock(), 'foo', mock.Mock())
+        self.ewhi.assert_called_once_with(mock.ANY, mock.ANY, 'foo', mock.ANY)
+
+    def test_init_new_style_empty_client(self):
+        conn_state = ['', mock.Mock(), mock.Mock()]
+        # have to make a copy since the init will modify what we pass
+        csc = copy.copy(conn_state)
+        csc[0] = ('<local>', 0)
+        utils.UnixDomainHttpProtocol(conn_state, mock.Mock())
+        self.ewhi.assert_called_once_with(mock.ANY, csc, mock.ANY)
+
+    def test_init_new_style_client(self):
+        conn_state = ['foo', mock.Mock(), mock.Mock()]
+        utils.UnixDomainHttpProtocol(conn_state, mock.Mock())
+        self.ewhi.assert_called_once_with(mock.ANY, conn_state, mock.ANY)
+
+    def test_init_unknown_client(self):
+        utils.UnixDomainHttpProtocol('foo')
+        self.ewhi.assert_called_once_with(mock.ANY, 'foo')
 
 
 class TestUnixDomainWSGIServer(base.BaseTestCase):