Nginx Alias vs Rewrite

Question

I have two working configurations that, on the surface, seem to do the same thing. They both accomplish the functionality that I need:

location ~ ^/(css|images|js)/ {
    location ~ '^/(css|js)/[0-9]{8}-(.*)$' {
        alias /$1/$2;
    }
    root /server/path/to/web/root;
}

AND

location ~ ^/(css|images|js)/ {
    rewrite '^/(css|js)/[0-9]{8}-(.*)$' /$1/$2 break;
    root /server/path/to/web/root;
}

They both take a URL like /css/87654321-styles.css and deliver the file /css/styles.css. I lean toward the second solution because it's more succinct, but I don't know if one is better than the other for performance reasons, unintended side-effects, etc.

Here's my original SO post, for reference/context.

After being directed to the documentation for the Nginx rewrite module, I found these interesting lines:

The ngx_http_rewrite_module module directives are processed in the following order:

• the directives of this module specified on the server level are executed sequentially;
• repeatedly:
  • a location is searched based on a request URI;
  • the directives of this module specified inside the found location are executed sequentially;
  • the loop is repeated if a request URI was rewritten, but not more than 10 times.

So, if I used the rewrite directive without the break flag, there could be at least one additional loop of the server level directive.

Answer 1

1. alias is like root, so you need to use full server path

2. You can add break flag to rewrite to avoid an internal redirect. Without break Nginx will start to process all location blocks from beginning. break tells to Nginx to use the current location instead.

I don't think there's a big difference in performance here. Main difference is changing request URI ($uri). But in the case of serving static files both work well.