Fix #94: allow pickling Logger objects

cloudpickle/cloudpickle.py

@@ -47,6 +47,7 @@
 import imp
 import io
 import itertools
+import logging
 import opcode
 import operator
 import pickle
@@ -569,6 +570,12 @@ def save_inst(self, obj):
         Supports __transient__"""
         cls = obj.__class__
 
+        # Try the dispatch table (pickle module doesn't do it)
+        f = self.dispatch.get(cls)
+        if f:
+            f(self, obj)  # Call unbound method with explicit self
+            return
+
         memo = self.memo
         write = self.write
         save = self.save
@@ -795,6 +802,11 @@ def inject_addons(self):
         """Plug in system. Register additional pickling functions if modules already loaded"""
         pass
 
+    def save_logger(self, obj):
+        self.save_reduce(logging.getLogger, (obj.name,), obj=obj)
+
+    dispatch[logging.Logger] = save_logger
+
 
 # Tornado support
 

tests/cloudpickle_test.py

@@ -1,16 +1,26 @@
 from __future__ import division
-import imp
-import unittest
-import pytest
-import pickle
-import sys
-import random
+
+import base64
 import functools
+import imp
+from io import BytesIO
 import itertools
+import logging
+from operator import itemgetter, attrgetter
+import pickle
 import platform
-import textwrap
-import base64
+import random
 import subprocess
+import sys
+import textwrap
+import unittest
+
+try:
+    from StringIO import StringIO
+except ImportError:
+    from io import StringIO
+
+import pytest
 
 try:
     # try importing numpy and scipy. These are not hard dependencies and
@@ -27,16 +37,6 @@
 except ImportError:
     tornado = None
 
-
-from operator import itemgetter, attrgetter
-
-try:
-    from StringIO import StringIO
-except ImportError:
-    from io import StringIO
-
-from io import BytesIO
-
 import cloudpickle
 from cloudpickle.cloudpickle import _find_module, _make_empty_cell, cell_set
 
@@ -507,6 +507,28 @@ def test_cell_manipulation(self):
             msg='cell contents not set correctly',
         )
 
+    def test_logger(self):
+        logger = logging.getLogger('cloudpickle.dummy_test_logger')
+        pickled = pickle_depickle(logger)
+        self.assertTrue(pickled is logger, (pickled, logger))
+
+        dumped = cloudpickle.dumps(logger)
+
+        code = """if 1:
+            import cloudpickle, logging
+
+            logging.basicConfig(level=logging.INFO)
+            logger = cloudpickle.loads(%(dumped)r)
+            logger.info('hello')
+            """ % locals()
+        proc = subprocess.Popen([sys.executable, "-c", code],
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.STDOUT)
+        out, _ = proc.communicate()
+        self.assertEqual(proc.wait(), 0)
+        self.assertEqual(out.strip().decode(),
+                         'INFO:cloudpickle.dummy_test_logger:hello')
+
 
 if __name__ == '__main__':
     unittest.main()