Nginx map value not matched when used as input of another map

[Maxim Dounin]

Hello!

On Mon, Jul 18, 2016 at 01:59:06PM -0400, Linna.Ding wrote:

> I just tested with a single map "cache_key", and the rate limiting doesn't
> work, the $cache_key was logged as empty string. But changing
> $upstream_cache_status to non-upstream variables like $remote_addr and
> adding an IP match value will make the rate limiting work.
> The zone I defined like so:
>        limit_req_zone $cache_key zone=cache_host:1m rate=1r/m;
>        map $upstream_cache_status $cache_key {
>            HIT $host;
>            EXPIRED $host;
>            - $host;
>            default "";
>         }
> And I use it in one of my server chunk with limit_req directive below:
>     limit_req zone=cache_host busrt=1;
> 
> Since I am using Nginx as reverse proxy, is this because
> $upstream_cache_status value is set after the request is sent to origin
> server and got the response, while $cache_key is used in rate limit zone
> which checked before the request was sent to origin server?
> If so, is there a recommended way to implement rate limiting only for
> request that MISS cache?

This doesn't looks like a development-related question.  Please 
use the nginx@ mailing list instead, see 
http://nginx.org/en/support.html.

-- 
Maxim Dounin
http://nginx.org/