core: cache result of unpickling message.

mitogen/core.py

@@ -281,6 +281,7 @@ class Message(object):
     handle = None
     reply_to = None
     data = ''
+    _unpickled = object()
 
     router = None
     receiver = None
@@ -324,15 +325,18 @@ class Message(object):
     def unpickle(self, throw=True, throw_dead=True):
         """Deserialize `data` into an object."""
         _vv and IOLOG.debug('%r.unpickle()', self)
-        fp = cStringIO.StringIO(self.data)
-        unpickler = cPickle.Unpickler(fp)
-        unpickler.find_global = self._find_global
+        obj = self._unpickled
+        if obj is Message._unpickled:
+            fp = cStringIO.StringIO(self.data)
+            unpickler = cPickle.Unpickler(fp)
+            unpickler.find_global = self._find_global
 
-        try:
-            # Must occur off the broker thread.
-            obj = unpickler.load()
-        except (TypeError, ValueError), ex:
-            raise StreamError('invalid message: %s', ex)
+            try:
+                # Must occur off the broker thread.
+                obj = unpickler.load()
+                self._unpickled = obj
+            except (TypeError, ValueError), ex:
+                raise StreamError('invalid message: %s', ex)
 
         if throw:
             if obj == _DEAD and throw_dead: