Don't set the etag header if the handler already did it.

diff --git a/tornado/web.py b/tornado/web.py
index 766a441ffe90b9584a3044c543ba0f43a8e4b89d..f1ee8ee57da40c7d02c2a4b5884f379d48c1daa7 100644 (file)
--- a/tornado/web.py
+++ b/tornado/web.py
@@ -469,7 +469,8 @@ class RequestHandler(object):
         # Automatically support ETags and add the Content-Length header if
         # we have not flushed any content yet.
         if not self._headers_written:
-            if self._status_code == 200 and self.request.method == "GET":
+            if (self._status_code == 200 and self.request.method == "GET" and
+                "Etag" not in self._headers):
                 hasher = hashlib.sha1()
                 for part in self._write_buffer:
                     hasher.update(part)