Fix non-threadsafe failure in serializer - now using thread local serializer instance.

dddp/msg.py

@@ -1,15 +1,17 @@
 """Django DDP utils for DDP messaging."""
-import collections
+from dddp import THREAD_LOCAL as this
 from django.core.serializers import get_serializer
 
-_SERIALIZER = None
+
+def serializer_factory():
+    """Make a new DDP serializer."""
+    return get_serializer('ddp')()
+
 
 def obj_change_as_msg(obj, msg):
     """Generate a DDP msg for obj with specified msg type."""
-    global _SERIALIZER
-    if _SERIALIZER is None:
-        _SERIALIZER = get_serializer('ddp')()
-    data = _SERIALIZER.serialize([obj])[0]
+    serializer = this.get('serializer', serializer_factory)
+    data = serializer.serialize([obj])[0]
     name = data['model']
 
     # cast ID as string