[Zope] ZServer (Zope 2.1.6) thread synchronization bug -- with workaround

[Dr. Dieter Maurer]

ZServer contains a thread synchronization bug
exposed when the HTTP streaming protocol
(i.e. RESPONSE.write) is used.

For large responses, the reponse is written
to a temporary file and the distribution
thread receives "file_part_producer" requests.
Writing to the tempfile uses "seek => write"
in the request thread; reading the tempfile
uses "seek => read" in the distribution thread.
The threads are not synchronized. This may
result in loss of response data: broken or buggy
images/files.


The following patch removes the use of
a tempfile. This, of cause, is only a
crude workaround.

Dieter
*******************************************************************
--- ZServer/:HTTPResponse.py	Mon Jan 24 20:17:53 2000
+++ ZServer/HTTPResponse.py	Thu Jun  8 09:01:31 2000
@@ -239,7 +239,9 @@
                 try:
                     if type(l) is type(''): l=string.atoi(l)
                     if l > 128000:
-                        self._tempfile=tempfile.TemporaryFile()
+		        # don't! exposes a thread synchronization problem
+                        # self._tempfile=tempfile.TemporaryFile()
+			pass
                 except: pass
                     
             stdout.write(str(self))