Allow ClientSession objects to get cleaned up by the garbage collector

Fixes #1652

koji/__init__.py

@@ -77,6 +77,7 @@ import tempfile
 import time
 import traceback
 import warnings
+import weakref
 import xml.sax
 import xml.sax.handler
 import six.moves.urllib
@@ -2141,7 +2142,10 @@ class ClientSession(object):
         self.opts = opts
         self.authtype = None
         self.setSession(sinfo)
-        self._multicall = MultiCallHack(self)
+        # Use a weak reference here so the garbage collector can still clean up
+        # ClientSession objects even with a circular reference, and the optional
+        # cycle detector being disabled due to the __del__ method being used.
+        self._multicall = MultiCallHack(weakref.ref(self))
         self._calls = []
         self.logger = logging.getLogger('koji')
         self.rsession = None
@@ -2889,6 +2893,9 @@ class MultiCallHack(object):
 
     def __init__(self, session):
         self.value = False
+        # session must be a weak reference
+        if not isinstance(session, weakref.ReferenceType):
+            raise TypeError('The session parameter must be a weak reference')
         self.session = session
 
     def __nonzero__(self):
@@ -2898,7 +2905,9 @@ class MultiCallHack(object):
         return self.value
 
     def __call__(self, **kw):
-        return MultiCallSession(self.session, **kw)
+        # self.session is a weak reference, which is why it is being called
+        # first
+        return MultiCallSession(self.session(), **kw)
 
 
 class MultiCallNotReady(Exception):

tests/test_lib/test_client_session.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 import mock
 import six
+import weakref
 try:
     import unittest2 as unittest
 except ImportError:
@@ -227,3 +228,11 @@ class TestMultiCall(unittest.TestCase):
         self.assertEqual(2, self.ksession._sendCall.call_count)
         self.assertEqual([['a', 'b', 'c'],
                           {'faultCode': 1000, 'faultString': 'msg'}], ret)
+
+    def test_MultiCallHack_weakref_validation(self):
+        expected_exc = 'The session parameter must be a weak reference'
+        with self.assertRaisesRegexp(TypeError, expected_exc):
+            koji.MultiCallHack(self.ksession)
+
+        # This should not raise an exception
+        koji.MultiCallHack(weakref.ref(self.ksession))