memcache and proxy

[Maxim Dounin]

Hello!

On Wed, Sep 03, 2008 at 02:23:50PM +0000, Paul B wrote:

>I am using nginx as the front end for our website, proxying PHP requests off to
>another server. 
>I want to make sure nginx catches 502 and 504 errors (incase the php backend is
>down) and redirect these errors to a static page.
>
>So i have this working fine
>
>
>#serve static pages with nginx
>location ~* ^.+\.(swf|xml|png|html|jpg|jpeg|gif|pdf|ico|css|js)$ { 
>root /data/htdocs/;
>}
>
>#proxy the rest to backend
>location / {
> index    index.php ;
>        error_page       504 = /index.html;
>        error_page       502 = /index.html;
> proxy_pass  http://10.100.250.100:88;
>}
>
>
>If my backend is working, site works fine, if i shut down the php server i get
>the index.html page. Works like a charm.
>
>However, I want to also use memcache, so that some php pages can get served from
>cache and not have to be sent to the backend
>
>so i change this to my conf
>
>location / {
>index    index.php ;
>set $memcached_key "guest:Action:$uri";
>memcached_pass   10.100.250.101:11220;
>default_type     text/html;
>error_page       404 = /fallback;
>    }
>
>location = /fallback {
>        proxy_pass       http://10.100.250.100:88;
>        error_page       502 = /index.html;
>        error_page       504 = /index.html;
>    }
>
>
>When my backend server is up, this too works fine. I can store pages in cache
>and they get displayed and if the page isnt in cache, the backed will serve it
>up. However, if i shutdown my backend server, the 502 and 504 redirects no
>longer work. I see the 502 Bad Gateway nginx/0.6.32 error page. Nothing i do
>seems to fix this. As soon as i add the fallback location for memcache, i can no
>longer catch the 502 or 504 errors. 
>
>any idea how to fix this???

http://wiki.codemongers.com/NginxHttpCoreModule#recursive_error_pages

Maxim Dounin