- From: Adrien de Croy <adrien@qbik.com>
- Date: Fri, 19 Jun 2009 22:38:26 +1200
- To: HTTP Working Group <ietf-http-wg@w3.org>
Hi I'm seeing a few problem sites, where the server replies with a 304 to a conditional request, but the ETag doesn't match any known ETag. E.g from a packet capture: GET /economics/charts/nzdusd_1_hourly.gif HTTP/1.1 Host: www.nationalbank.co.nz User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/530.5 (KHTML, like Gecko) Chrome/2.0.172.31 Safari/530.5 Referer: http://www.nationalbank.co.nz/economics/exchange/nzdusd.aspx Accept: */* Accept-Encoding: gzip,deflate,bzip2,sdch Cookie: s_vi=[CS]v1|499E6E6A00006868-A0208AF00000004[CE]; s_nr=1244358115085; s_cc=true; s_sq=%5B%5BB%5D%5D Accept-Language: en-US,en;q=0.8 Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.3 If-Modified-Since: Fri, 19 Jun 2009 10:19:38 GMT If-None-Match: "8042c973c7f0c91:64e6" Connection: Keep-Alive HTTP/1.1 304 Not Modified Server: Microsoft-IIS/5.0 Date: Fri, 19 Jun 2009 10:27:31 GMT X-Powered-By: ASP.NET Cache-Control: no-cache Expires: Fri, 19 Jun 2009 10:27:31 GMT ETag: "08de660c7f0c91:6a9f" Content-Length: 0 Apart from the known IIS bug with Content-Length: 0, how is an intermediary cache to deal with this? Is it allowable to change an ETag on a stored representation? Isn't the whole point of an ETag that it uniquely identifies a rep, and so a different ETag means a different representation? The 304 is pretty clear, whatever the client asked for hasn't changed. But what if there were more than one ETag in the request? Which stored representation would one update? the latest? Does this mean it's generally a really bad idea to have more than 1 Etag in a If-None-Match header, or at least more than 1 added by an intermediary cache? IOW is it a really bad idea for an intermediary to try and use If-None-Match to see which stored representation is the one that's still valid? In terms of the spec, it says you must always serve the stored rep with the latest Date header, but what about for revalidation? Thanks Adrien -- Adrien de Croy - WinGate Proxy Server - http://www.wingate.com
Received on Friday, 19 June 2009 10:35:47 UTC