Ruby Forum NGINX > memcache and proxy

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???

Hello!

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

>root /data/htdocs/;
>
>set $memcached_key "guest:Action:$uri";
>
>
>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

Maxim Dounin <mdounin@...> writes:


> 
> http://wiki.codemongers.com/NginxHttpCoreModule#recursive_error_pages
> 
> Maxim Dounin
> 
> 

Excellent, I knew it would have a simple answer.
Hopefully there is an as simple fix to the next problem i have
again concerning memcache and proxy

I have a url
http://my.domain.com/something/one

i don't cache it, so it passes it to the proxy.

What the page should do is a simple redirect to

http://my.domain.com/something/one/content

If i remove my memcache line, so that everything in location / goes to
 proxy_pass  http://backend;

it works
If i go direct to the proxy port, it works
However, using my memcache config, it passes it to my /fallback 
locations and it
stops working. I get a blank page in my browser and it doesn't redirect. 
I can
check the logs of my backend, and I see exactly the same request either 
way, it
is just that when i pass it to /fallback, the redirect does not seem to 
get
passed back to nginx.