load balancing and caching combination problem

[Maxim Dounin]

Hello!

On Mon, Aug 31, 2009 at 04:57:01AM -0400, fredericsidler wrote:

> I just installed nginx 0.8.11 in order to use the $upstream_cache_status variable.
> 
> I can see now in the logs that my URLs (ics feed URLs) are cached and retrieved from the cache (MISS, HIT, EXPIRED) based on my caching parameters.
> 
> But, it only works when
>             proxy_ignore_headers Cache-Control;
>             proxy_ignore_headers Expires;
> 
> are used and left uncommented. I have read in the forums that this shouldn't be use in production. So what should I do next to be able to comment these parameters and get the result I'm expected.

Directive proxy_ignore_headers instruct nginx to *ignore* headers 
in question got from upstream.  And as you have Cache-Control 
returned by your upstream - nginx honors it unless 
proxy_ignore_headers specified.  There is nothing wrong here.

Best solution would be to fix upstream server to return cache-related 
headers you want.  If you can't do that for some reason - the only 
way is to use proxy_ignore_headers.

> I tried to set the Expires header by using set_proxy_header, but no headers are added to my file. Here is my configuration file and the headers of one the ICS file

Directive proxy_set_header sets headers sent to upstream, it's 
completely unrelated.  There is no way to alter upstream response 
before caching it.

Maxim Dounin

> 
> nginx.conf
> 
> user www-data;
> worker_processes  4;
> 
> error_log  /var/log/nginx/error.log;
> pid        /var/run/nginx.pid;
> 
> events {
>     worker_connections  4096;
> }
> 
> http {
>     include       /etc/nginx/mime.types;
>     default_type  application/octet-stream;
> 
>     log_format fbcal '$remote_addr - $remote_user [$time_local]  '
>                      '"$request" $status $body_bytes_sent '
>                      '"$http_referer" "$http_user_agent"'
>                      '"$upstream_cache_status"';
> 
>     access_log  /var/log/nginx/access.log fbcal;
> 
>     sendfile        on;
> 
>     keepalive_timeout  30;
>     tcp_nodelay        on;
> 
>     include /etc/nginx/app-servers.include;
> 
>     proxy_cache_path /var/www/fbcaldotcom/cache levels=1:2 keys_zone=one:10m;
>     proxy_temp_path   /temp/cache;
> 
>     server {
>         listen       80;
> 
>         if ( $remote_addr = 127.0.0.1 ) {
>             rewrite   ^(.*)$  /500.html last;
>             return 302;
> 
>         }
> 
>         location /    {
>             proxy_pass         http://backend;
> 
>             proxy_cache one;
>             proxy_cache_key         backend$request_uri;
>             proxy_cache_valid 200 3h;
>             proxy_cache_use_stale   error timeout invalid_header;
> #            proxy_ignore_headers Cache-Control;
> #            proxy_ignore_headers Expires;
> 
>             proxy_set_header   Host             $host;
>             proxy_set_header   X-Real-IP        $remote_addr;
>             proxy_set_header   X-Forwarded-For  $proxy_add_x_forwarded_for;
> 
>             error_page   500 501  =  /500.html;
>             error_page   502 503 504  =  /502.html;
>         }
> 
>         location /500.html {
>                 root   /var/www/nginx-default;
>         }
> 
>         location /502.html {
>                 root   /var/www/nginx-default;
>         }
> 
>     }
> 
> }
> 
> curl -I
> 
> HTTP/1.1 200 OK
> Server: nginx/0.8.11
> Date: Mon, 31 Aug 2009 08:41:57 GMT
> Content-Type: text/calendar; charset=utf-8
> Connection: keep-alive
> X-Powered-By: PHP/5.2.4-2ubuntu5.7
> Content-Disposition: attachment; filename="fbCal-Events.ics"
> Cache-Control: max-age=10
> Content-Length: 80450
> 
> Posted at Nginx Forum: http://forum.nginx.org/read.php?2,5392,5392#msg-5392
> 
>