clearing etags when gzipping

[Maxim Dounin]

Hello!

On Thu, Nov 22, 2012 at 08:05:57PM -0500, Jeff Kaufman wrote:

> On Wed, Nov 21, 2012 at 4:02 PM, Maxim Dounin <mdounin at mdounin.ru> wrote:
> >
> > >
> > > What would you think of simply not clearing the etag when it's already weak?
> >
> > I think it would be ok.
> >
> 
> How do you want patches submitted?  Is this good?
> 
> --- nginx-1.3.8/src/http/modules/ngx_http_gzip_filter_module.c
> 2012-07-07 17:22:27.000000000 -0400
> +++ nginx-1.3.8-weak-etags-shorter/src/http/modules/ngx_http_gzip_filter_module.c2012-11-21
> 17:05:12.758389000 -0500
> @@ -306,7 +306,15 @@
> 
>      ngx_http_clear_content_length(r);
>      ngx_http_clear_accept_ranges(r);
> -    ngx_http_clear_etag(r);
> +
> +    /* Clear etags unless they're marked as weak (prefixed with 'W/') */
> +    h = r->headers_out.etag;
> +    if (h && !(h->value.len >= 3 &&
> +               h->value.data[0] == 'W' &&
> +               h->value.data[1] == '/' &&
> +               h->value.data[2] == '"')) {
> +      ngx_http_clear_etag(r);
> +    }
> 
>      return ngx_http_next_header_filter(r);
>  }

Uhm, this is not something I would like to commit.  It should be a 
macro, probably something like

    ngx_http_clear_strong_etag(r);

Much like ngx_http_clear_etag() itself.

It would be also good idea to audit other uses of 
ngx_http_clear_etag() to see if they also deserve changing to a 
new macro introduced.  Rule of thumb seems to be: we want to 
clear strong etags only if we clear Accept-Ranges but not 
Last-Modified.

Style also needs fixing to match one used in nginx.

-- 
Maxim Dounin
http://nginx.com/support.html