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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=7847 Reverse proxy server caching 304 responses from origin server Summary: Reverse proxy server caching 304 responses from origin server Product: Apache httpd-1.3 Version: 1.3.24 Platform: PC URL: http://www.dreo.dnd.ca http://www.drdc-rddc.dnd.ca OS/Version: FreeBSD Status: NEW Severity: Normal Priority: Other Component: mod_proxy AssignedTo: bugs@httpd.apache.org ReportedBy: [EMAIL PROTECTED] Hello, To start with Some Background follows We are using Apache 1.3.24 as a reverse proxy server with caching enabled for some internal web sites. We discovered that when we attempt to force a reload of the web page from the origin server using our web browser, we are simply getting back a blank page. This problem is reproducable. This works in IE 5.5 and Mozilla 0.9.9 and Netscape 4.79. To issue the reload from the origin server from IE 5.5, type "Ctrl-F5". To issue the reload from the origin server from Mozilla and Netscape, hold "Ctrl" and click the "Reload" button. By doing this, it sets "Cache-Control" in the HTTP/1.1 request to "No cache". We found that this only works when the origin server is MS IIS 4.0. When the origin server is an Apache server, the web page is refreshed from the cache of the reverse proxy server. More Detailed Information The Internal origin server is an MS IIS 4.0 for www.dreo.dnd.ca. This will work for any page that is cached on the reverse proxy server. The page we will use for testing is http://www.dreo.dnd.ca/ which has already been previously cached on the reverse proxy server. Using a sniffer on the reverse proxy server we determined what the HTTP/1.1 request was from the browser client: GET / HTTP/1.1 Accept: */* Accept-Language: en-us Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE.5.5; Windows.NT 4.0) Host: www.dreo.dnd.ca. Connection: Keep-Alive Cache-Control: no-cache When the reverse proxy receives this request it forwards it onto the internal origin server with a couple of additional fields (why does it send an HTTP/1.0 request instead of the original HTTP/1.1 request?) : GET / HTTP/1.0 Host: www.dreo.dnd.ca Accept: */* Accept-Encoding: gzip, deflate Accept-Language: en-us Cache-Control: no-cache User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 4.0) If-Modified-Since: Wed, 08 Nov 2000 18:10:04 GMT If-None-Match: "c077721eaf49c01:1364" X-Forwarded-For: xxx.xxx.244.1 Connection: close The origin server then returns the following: HTTP/1.1 304 Not Modified Server: Microsoft-IIS/4.0 Date: Thu, 04 Apr 2002 16:05:15 GMT Content-Location: http://www.dreo.dnd.ca/index.html ETag: "c077721eaf49c01:1364" Content-Length: 0 This "304 Not Modified" is then cached on the reverse proxy server and the following is served back to the client with no HTML content from the previously cached page (a blank page is displayed as a result): HTTP/1.1 200 OK Date: Thu, 04 Apr 2002 16:05:34 GMT Server: Apache/1.3.24 (Unix) Accept-Ranges: bytes Content-Length: 0 Content-Location: http://www.dreo.dnd.ca/index.html Content-Type: text/html ETag:."c077721eaf49c01:1364" Last-Modified: Wed, 08 Nov 2000 18:10:04 GMT X-Cache: HIT from www.dreo.dnd.ca (with.revalidation) Keep-Alive: timeout=15, max=100 Connection: Keep-Alive When the Internal origin server is Apache, the difference in the "304 Not Modified" returned to the reverse proxy server is there is no "Content-Length: 0" header returned. The error_log file (with debugging enabled) on the reverse proxy server shows the following: [Fri Apr 5 15:51:37 2002] [debug] proxy_cache.c(1018): Request for http://www.dreo.dnd.ca/, pragma_req=(null), ims=0 [Fri Apr 5 15:51:37 2002] [debug] proxy_util.c(1373): File /var/proxy/drdc/3G/mQ/sM/[EMAIL PROTECTED] not found [Fri Apr 5 15:51:37 2002] [debug] proxy_cache.c(1271): Local copy not present or expired. Declining. [Fri Apr 5 15:51:38 2002] [debug] proxy_cache.c(1457): Expiry date is 0 [Fri Apr 5 15:51:38 2002] [debug] proxy_cache.c(1468): Expiry date calculated 1018126298 [Fri Apr 5 15:51:38 2002] [debug] proxy_cache.c(1575): Create temporary file /var/proxy/drdc/tmpN80355 [Fri Apr 5 15:51:38 2002] [debug] proxy_http.c(537): Content-Type: text/html [Fri Apr 5 15:51:51 2002] [debug] proxy_cache.c(1018): Request for http://www.dreo.dnd.ca/, pragma_req=(null), ims=0 [Fri Apr 5 15:51:51 2002] [debug] proxy_cache.c(1271): Local copy not present or expired. Declining. [Fri Apr 5 15:51:51 2002] [debug] proxy_cache.c(1441): Reusing cached last modified [Fri Apr 5 15:51:51 2002] [debug] proxy_cache.c(1457): Expiry date is 0 [Fri Apr 5 15:51:51 2002] [debug] proxy_cache.c(1468): Expiry date calculated 1018126311 The access_log shows the following on the reverse proxy server: xxx.xxx.244.1 - - [05/Apr/2002:15:51:38 -0500] "GET / HTTP/1.1" 200 2557 xxx.xxx.244.1 - - [05/Apr/2002:15:51:51 -0500] "GET / HTTP/1.1" 200 0 If you think that there is something else that you need from us to debug this let me know. Thanks Robert Tovell [EMAIL PROTECTED]
