# Proxy\_cache\_bypass with ssi caches template **URL:** \ **Category:** NGINX\ **Created:** [January 10, 2011, 8:56pm UTC](https://www.ruby-forum.com/t/proxy-cache-bypass-with-ssi-caches-template/201562 "2011-01-10T20:56:30Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dubstep](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/cdc98d/32.png) [@dubstep](https://www.ruby-forum.com/u/dubstep)\ **Post date:** [January 10, 2011, 8:56pm UTC](https://www.ruby-forum.com/t/proxy-cache-bypass-with-ssi-caches-template/201562/1 "2011-01-10T20:56:30Z")
Hi everyone, I’ve been struggling with this for some time now trying to drop varnish in favor for nginx. Server: nginx/0.8.54 quick peek on problem - SSI on; proxy\_cache\_bypass caches backend response as regular html page with HTTP/1.1 200 OK inside, so next fetch from cache will return to client a page with SSI tags inside (unprocessed). And now the full configuration if the problem is still not clear. My goal: force refresh of item in cache Item has SSI tags inside which I would like to be processed (this is obvious) So far I’ve found that there’s no way of refreshing cache other than deleting a file on hdd (which could lead to strange problems in my opinion) or using proxy\_cache\_bypass. Bypass goes right to backend and the response is cached, but with ssi on it’s cached wrong. Configuration: - debian6-32 (running nginx 0.8.54) - bypass will be used when ‘Secret’ header is set - backend has two files - index.php and footer.php Step 1) first fetch (without bypass) returns this: ```auto [20:45:01] debian6-32:~# printf "GET /num/5 HTTP/1.0\r\nHost: debian6-32\r\n\r\n" | nc.traditional debian6-32 80 | grep '>' >>>> FOOTER 08:46:05 >>>> INDEX 08:46:05 [20:45:08] debian6-32:~# printf "GET /num/5 HTTP/1.0\r\nHost: debian6-32\\r\n\r\n" | nc.traditional debian6-32 80 | grep '>' >>>> FOOTER 08:46:05 >>>> INDEX 08:46:05 ``` We can see that cache and SSI works fine (footer line is produced by footer.php) and the whole page is cached Step 2) let’s refresh cache using secret header ```auto [20:45:16] ponury@eva:~ $ printf "GET /num/5 HTTP/1.0\r\nHost: debian6-32\r\nSecret: 1\r\n\r\n" | nc.traditional debian6-32 80 | grep '>>' >>>> FOOTER 08:47:09 >>>> INDEX 08:47:09 [20:45:18] ponury@eva:~ $ printf "GET /num/5 HTTP/1.0\r\nHost: debian6-32\r\nSecret: 1\r\n\r\n" | nc.traditional debian6-32 80 | grep '>>' >>>> FOOTER 08:47:11 >>>> INDEX 08:47:11 [20:45:20] ponury@eva:~ $ ``` Also bypass works great each time backend is being hit. Step 3) fetch that page without bypass: ```auto [20:45:11] debian6-32:~# printf "GET /num/5 HTTP/1.0\r\nHost: debian6-32\r\nCookie: refresh=1\r\n\r\n" | nc.traditional debian6-32 80 | grep '>' >>>> INDEX 08:47:11 [20:45:23] debian6-32:~# ``` And here it is… clients receives unprocessed ssi header. The good news is - its fresh. Bad news - it shouldn’t happen. My current nginx config: [code] location / { ssi on; ``` proxy_cache my-cache; proxy_cache_valid 200 302 1m; if ($remote_addr ~* "192.168.0.128") { set $is_backend 1; } proxy_cache_bypass $is_backend $http_secret; proxy_pass http://192.168.0.128$uri$is_args$args; } ``` [/code] So, is there something I’m missing or this just can’t be done? Thank you in advance for any help. Posted at Nginx Forum: > **[proxy\_cache\_bypass with ssi caches template](https://forum.nginx.org/read.php?2,165196,165196#msg-165196)** > > Hi everyone, I've been struggling with this for some time now trying to drop varnish in favor for nginx. Server: nginx/0.8.54 quick peek on problem - SSI on; proxy\_cache\_bypass caches backend response as regular html page with HTTP/1.1 200 OK inside,... ---
**Author:** ![bponury](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/5daacb/32.png) [@bponury](https://www.ruby-forum.com/u/bponury)\ **Post date:** [January 11, 2011, 12:32am UTC](https://www.ruby-forum.com/t/proxy-cache-bypass-with-ssi-caches-template/201562/2 "2011-01-11T00:32:26Z")
Hello! On Mon, Jan 10, 2011 at 02:55:04PM -0500, bponury wrote: > Hi everyone, > I’ve been struggling with this for some time now trying to drop varnish > in favor for nginx. > > Server: nginx/0.8.54 > > quick peek on problem - SSI on; proxy\_cache\_bypass caches backend > response as regular html page with HTTP/1.1 200 OK inside, so next fetch > from cache will return to client a page with SSI tags inside > (unprocessed). […] > So, is there something I’m missing or this just can’t be done? The problem is that proxy\_cache\_bypass doesn’t work as of now (it usually corrupts response headers, though may corrupt response body/cause other problems as well). It may only be used with identical proxy\_no\_cache. The problem you see with SSI is related to corrupted response headers - response no longer has Content-Type and not processed by SSI as a result. Maxim D. ---
**Author:** ![bponury](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/5daacb/32.png) [@bponury](https://www.ruby-forum.com/u/bponury)\ **Post date:** [January 11, 2011, 2:09am UTC](https://www.ruby-forum.com/t/proxy-cache-bypass-with-ssi-caches-template/201562/3 "2011-01-11T02:09:48Z")
## Maxim D. Wrote: > The problem is that proxy\_cache\_bypass doesn’t > work as of now (it > usually corrupts response headers, though may > corrupt response > body/cause other problems as well). It may only > be used with > identical proxy\_no\_cache. Well that makes sense now. I see that other headers are corrupted. Which brings us back to my question - what is the best way to force-refresh a page in cache? I want my backend to invalidate some pages as they change. And those pages could have SSI inside. I know that deleting a file from hdd works, but my invalidation requests will happen many times, removing and recreating files again and again could have performance impact. And it seems just wrong. Any help here? Posted at Nginx Forum: [http://forum.nginx.org/read.php?2,165196,165248#msg-165248](http://forum.nginx.org/read.php?2,165196,165248#msg-165248) ---
**Author:** ![bponury](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/5daacb/32.png) [@bponury](https://www.ruby-forum.com/u/bponury)\ **Post date:** [January 11, 2011, 2:36am UTC](https://www.ruby-forum.com/t/proxy-cache-bypass-with-ssi-caches-template/201562/4 "2011-01-11T02:36:44Z")
Hello! On Mon, Jan 10, 2011 at 08:08:05PM -0500, bponury wrote: > Well that makes sense now. I see that other headers are corrupted. > > Which brings us back to my question - what is the best way to > force-refresh a page in cache? I want my backend to invalidate some > pages as they change. And those pages could have SSI inside. I know that > deleting a file from hdd works, but my invalidation requests will happen > many times, removing and recreating files again and again could have > performance impact. And it seems just wrong. Any help here? Right now the only option is to remove cache files, either directly or with cache purge module. Maxim D.