A try_files problem

[Igor Sysoev]

On Thu, Mar 05, 2009 at 08:52:42PM +0100, Micha?? Jaszczyk wrote:

> I'm having some hard time with try_files and rewrite directives. I
> already spent few hours on this and my brain is exploding :). Can
> anyone help me?
> 
> My situation is as follows: I use Nginx to serve static files and
> proxy dynamic requests to Python backends. That's simple and my config
> file looks like this:
> 
> upstream backend {
>     http://backend1/;
>     # more backends
> }
> 
> location /static {
>     root /some/path;
>     # some other stuff
> }
> 
> location /dynamic {
>     rewrite ^/dynamic/(.*)$ /$1 break;
>     proxy_pass http://backend;
> }

This can be handled by simple:

 location /dynamic/ {
     proxy_pass http://backend/;
 }

> My dynamic content has this property: It doesn't change over time. So
> each time I send the same request to the backends, the response will
> always be the same. So I can mirror it using proxy_store:
> 
> location /dynamic {
>     rewrite ^/dynamic/(.*)$ /$1 break;
>     try_files $uri @backend;
> }
>
> location @backend {
>     proxy_pass http://backend;
>     proxy_store $uri;
> }

location /dynamic/ {
    alias      /path/to/;
    try_files  $uri  /backend/$uri;
}

location /backend/dynamic/ {
    proxy_pass   http://backend/;

    alias        /path/to/;
    proxy_store  on;
}

> This works just great. But there's one gotcha: Some of the requests to
> the backend have the following form: /special_request/ID. This ID has
> many potential values and if I mirror them the way described above, I
> will end up having a directory with tens (or hundreds) of thousands of
> files which will kill the file system eventually. So I did the
> following:
> 
> location @backend {
>     set $proxy_store_path $uri;
>     if ($uri ~ "^/special_request/([0-9]{2})([0-9]{2})(.*)$") {
>         set $proxy_store_path /$1/$2/$3;
>     }
>     proxy_pass http://backend;
>     proxy_store $proxy_store_path;
> }
> 
> This also works nice - instead of a flat directory with tons of files
> I have a nice 2-level hierarchy of directories. But... I also need to
> apply this idea to the /dynamic location. The most obvious approach
> is:
> 
> location /dynamic {
>     rewrite ^/dynamic/(.*)$ /$1 break;
>     set $try_files_path $uri;
>     if ($uri ~ "^/special_request/([0-9]{2})([0-9]{2})(.*)$") {
>         set $try_files_path /$1/$2/$3;
>     }
>     try_files $try_files_path @backend;
> }
> 
> But this doesn't work... I spent many hours trying to figure out how
> to deal with this, but no success so far... What's more interesting,
> in the log file I see a warning that $try_files_path is not
> initialized! How come??

You may try a patch in email with subject "captures in regex locations":

location ~ "^/dynamic/special_request/([0-9]{2})([0-9]{2})(.*)$" {
    set $proxy_store_path /$1/$2/$3;

    try_files  $proxy_store_path  /backend/$uri;
}

location /backend/dynamic/ {
    proxy_pass   http://backend/;

    proxy_store  $proxy_store_path;
}


-- 
Igor Sysoev
http://sysoev.ru/en/