Merge pull request #1692 from SURFscz/masterv17.2.0

Fix static file cached 304 response

4 files changed, 31 insertions, 3 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 6618df7e..44f377fc 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,9 @@
+v17.2.0
+-------
+
+* :issue:`1690`: Prevent orphaned Event object in cached
+  304 response.
+
 v17.1.0
 -------
 
diff --git a/cherrypy/_cprequest.py b/cherrypy/_cprequest.py
index f9943ff7..bde09891 100644
--- a/cherrypy/_cprequest.py
+++ b/cherrypy/_cprequest.py
@@ -2,9 +2,12 @@ import sys
 import time
 
 import uuid
+
 import six
 from six.moves.http_cookies import SimpleCookie, CookieError
 
+from more_itertools.recipes import consume
+
 import cherrypy
 from cherrypy._cpcompat import text_or_bytes, ntob
 from cherrypy import _cpreqbody
@@ -879,6 +882,14 @@ class Response(object):
         self.body = newbody
         return newbody
 
+    def _flush_body(self):
+        """
+        Discard self.body but consume any generator such that
+        any finalization can occur, such as is required by
+        caching.tee_output().
+        """
+        consume(iter(self.body))
+
     def finalize(self):
         """Transform headers (and cookies) into self.header_list. (Core)"""
         try:
@@ -903,6 +914,7 @@ class Response(object):
             # and 304 (not modified) responses MUST NOT
             # include a message-body."
             dict.pop(headers, 'Content-Length', None)
+            self._flush_body()
             self.body = b''
         else:
             # Responses which are not streamed should have a Content-Length,
diff --git a/cherrypy/lib/caching.py b/cherrypy/lib/caching.py
index aa265164..fed325a6 100644
--- a/cherrypy/lib/caching.py
+++ b/cherrypy/lib/caching.py
@@ -405,10 +405,19 @@ def tee_output():
             output.append(chunk)
             yield chunk
 
-        # save the cache data
+        # Save the cache data, but only if the body isn't empty.
+        # e.g. a 304 Not Modified on a static file response will
+        # have an empty body.
+        # If the body is empty, delete the cache because it
+        # contains a stale Threading._Event object that will
+        # stall all consecutive requests until the _Event times
+        # out
         body = b''.join(output)
-        cherrypy._cache.put((response.status, response.headers or {},
-                             body, response.time), len(body))
+        if not body:
+            cherrypy._cache.delete()
+        else:
+            cherrypy._cache.put((response.status, response.headers or {},
+                                 body, response.time), len(body))
 
     response = cherrypy.serving.response
     response.body = tee(response.body)
diff --git a/setup.py b/setup.py
index 3e2baa3f..79886904 100755
--- a/setup.py
+++ b/setup.py
@@ -63,6 +63,7 @@ params = dict(
         'six>=1.11.0',
         'cheroot>=6.2.4',
         'portend>=2.1.1',
+        'more_itertools',
     ],
     extras_require={
         'docs': [