[project @ robey@lag.net-20061215222108-7pu0151970w1e1lp]

add a ResourceManager to replace __del__ methods, and use it in SSHClient
to automatically close any open transport when the SSHClient is collected.
this won't work on Transport itself (to close the attached packetizer)
because Transport starts up its own thread, and the threading library
keeps a Transport object alive to run that thread.  i think that's okay;
the SSHClient interface is meant to be the easier one, so that's the one
where it's important that some auto-cleanup is attempted.

paramiko/client.py

@@ -28,6 +28,7 @@ from paramiko.agent import Agent
 from paramiko.common import *
 from paramiko.dsskey import DSSKey
 from paramiko.hostkeys import HostKeys
+from paramiko.resource import ResourceManager
 from paramiko.rsakey import RSAKey
 from paramiko.ssh_exception import SSHException, BadHostKeyException
 from paramiko.transport import Transport
@@ -256,6 +257,7 @@ class SSHClient (object):
         if self._log_channel is not None:
             t.set_log_channel(self._log_channel)
         t.start_client()
+        ResourceManager.register(self, t)
         
         server_key = t.get_remote_server_key()
         keytype = server_key.get_name()

paramiko/resource.py

@@ -0,0 +1,72 @@
+# Copyright (C) 2003-2006 Robey Pointer <robey@lag.net>
+#
+# This file is part of paramiko.
+#
+# Paramiko is free software; you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation; either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
+
+"""
+Resource manager.
+"""
+
+import weakref
+
+
+class ResourceManager (object):
+    """
+    A registry of objects and resources that should be closed when those
+    objects are deleted.
+    
+    This is meant to be a safer alternative to python's C{__del__} method,
+    which can cause reference cycles to never be collected.  Objects registered
+    with the ResourceManager can be collected but still free resources when
+    they die.
+    
+    Resources are registered using L{register}, and when an object is garbage
+    collected, each registered resource is closed by having its C{close()}
+    method called.  Multiple resources may be registered per object, but a
+    resource will only be closed once, even if multiple objects register it.
+    (The last object to register it wins.)
+    """
+    
+    def __init__(self):
+        self._table = {}
+        
+    def register(self, obj, resource):
+        """
+        Register a resource to be closed with an object is collected.
+        
+        When the given C{obj} is garbage-collected by the python interpreter,
+        the C{resource} will be closed by having its C{close()} method called.
+        Any exceptions are ignored.
+        
+        @param obj: the object to track
+        @type obj: object
+        @param resource: the resource to close when the object is collected
+        @type resource: object
+        """
+        def callback(ref):
+            try:
+                resource.close()
+            except:
+                pass
+            del self._table[id(resource)]
+
+        # keep the weakref in a table so it sticks around long enough to get
+        # its callback called. :)
+        self._table[id(resource)] = weakref.ref(obj, callback)
+
+
+# singleton
+ResourceManager = ResourceManager()

tests/test_client.py

@@ -23,6 +23,8 @@ Some unit tests for SSHClient.
 import socket
 import threading
 import unittest
+import weakref
+
 import paramiko
 
 
@@ -59,6 +61,7 @@ class SSHClientTest (unittest.TestCase):
         thread.start()
 
     def tearDown(self):
+        if hasattr(self, 'tc'):
             self.tc.close()
         self.ts.close()
         self.socks.close()
@@ -125,3 +128,26 @@ class SSHClientTest (unittest.TestCase):
         self.assertEquals(True, self.ts.is_authenticated())
         self.assertEquals(1, len(self.tc.get_host_keys()))
         self.assertEquals(public_host_key, self.tc.get_host_keys()[self.addr]['ssh-rsa'])
+
+    def test_3_cleanup(self):
+        """
+        verify that when an SSHClient is collected, its transport (and the
+        transport's packetizer) is closed.
+        """
+        host_key = paramiko.RSAKey.from_private_key_file('tests/test_rsa.key')
+        public_host_key = paramiko.RSAKey(data=str(host_key))
+        
+        self.tc = paramiko.SSHClient()
+        self.tc.set_missing_host_key_policy(paramiko.AutoAddPolicy())
+        self.assertEquals(0, len(self.tc.get_host_keys()))
+        self.tc.connect(self.addr, self.port, username='slowdive', password='pygmalion')
+
+        self.event.wait(1.0)
+        self.assert_(self.event.isSet())
+        self.assert_(self.ts.is_active())
+        
+        p = weakref.ref(self.tc._transport.packetizer)
+        self.assert_(p() is not None)
+        del self.tc
+        self.assert_(p() is None)
+