Always close sockets when defuncting connections

Under certain error conditions, this could result in an FD leak for the
socket handles.  (In my testing, they seemed to eventually be GC'ed and
closed, but this behavior is probably not dependable.)

Fixes #80

CHANGELOG.rst

@@ -6,6 +6,8 @@ Bug Fixes
 ---------
 * Include table indexes in ``KeyspaceMetadata.export_as_string()``
 * Fix broken token awareness on ByteOrderedPartitioner
+* Always close socket when defuncting error'ed connections to avoid a potential
+  file descriptor leak
 
 Other
 -----

cassandra/io/asyncorereactor.py

@@ -173,11 +173,11 @@ class AsyncoreConnection(Connection, asyncore.dispatcher):
         with _starting_conns_lock:
             _starting_conns.discard(self)
 
-        # don't leave in-progress operations hanging
-        self.connected_event.set()
         if not self.is_defunct:
             self._error_all_callbacks(
                 ConnectionShutdown("Connection to %s was closed" % self.host))
+            # don't leave in-progress operations hanging
+            self.connected_event.set()
 
     def defunct(self, exc):
         with self.lock:
@@ -194,6 +194,7 @@ class AsyncoreConnection(Connection, asyncore.dispatcher):
                       id(self), self.host, exc)
 
         self.last_error = exc
+        self.close()
         self._error_all_callbacks(exc)
         self.connected_event.set()
         return exc

cassandra/io/libevreactor.py

@@ -246,6 +246,7 @@ class LibevConnection(Connection):
             log.debug("Defuncting connection (%s) to %s: %s", id(self), self.host, exc)
 
         self.last_error = exc
+        self.close()
         self._error_all_callbacks(exc)
         self.connected_event.set()
         return exc