Forum: NGINX How to tell Proxy module to retrieve secondary URL if primary URL doenst exist

Hi all,

I am using nginx's Proxy module to retrieve images from Amazon S3. I 
need to
be able to tell the Proxy module to retrieve a smaller sized file if a
bigger sized file doesnt exist. How can I do that?

For instance, my nginx configuration:

  location / {
            proxy_pass   https://s3.amazonaws.com/my_bucket/;
            error_page   415 = /empty;
  }

Say I have image1_100.jpg on S3 then http://localhost/image1_100.jpg 
works
fine. However http://localhost/image1_300.jpg wont work. I want to be 
able
to ask nginx to request the
https://s3.amazonaws.com/my_bucket/image1_300.jpg file and if it doesnt
exist, request for iamge1_100.jpg file instead.

Thanks!

Posted at Nginx Forum: 
http://forum.nginx.org/read.php?2,231364,231364#msg-231364

Hello!

On Wed, Oct 03, 2012 at 05:00:39PM -0400, wurb32 wrote:

>             error_page   415 = /empty;
>   }
>
> Say I have image1_100.jpg on S3 then http://localhost/image1_100.jpg works
> fine. However http://localhost/image1_300.jpg wont work. I want to be able
> to ask nginx to request the
> https://s3.amazonaws.com/my_bucket/image1_300.jpg file and if it doesnt
> exist, request for iamge1_100.jpg file instead.

Use error_page 404 and proxy_intercept_errors, see
http://nginx.org/r/proxy_intercept_errors.

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

Hi ,

I tried with error_page and proxy_intercept_errors and it is not working 
for
me. Do you mind if you can give me an example configuration?

Posted at Nginx Forum: 
http://forum.nginx.org/read.php?2,231364,231389#msg-231389

Hello!

On Thu, Oct 04, 2012 at 12:08:55PM -0400, wurb32 wrote:

> Hi ,
>
> I tried with error_page and proxy_intercept_errors and it is not working for
> me. Do you mind if you can give me an example configuration?

Trivial config with fallback to a predefined static file would
look like:

    location / {
        error_page 404 = /fallback.jpg;

        proxy_pass http://upstream;
        proxy_intercept_errors on;
    }

    location = /fallback.jpg {
        # serve static file
    }

If you want rewrite from /something_300.jpg to /something_100.jpg
to happen automatically, for all possible values of "something",
then config like this should work, using named location and
rewrite:

    location / {
        error_page 404 = @fallback;

        proxy_pass http://upstream;
        proxy_intercept_errors on;
    }

    location @fallback {

        # if request ends with _300.jpg - rewrite to _100.jpg
        # and stop processing of rewrite rules, i.e. continue
        # with proxy_pass; else return 404

        rewrite ^(.*)_300.jpg$ $1_100.jpg break;
        return 404;

        proxy_pass http://upstream;
    }

Documentation:

http://nginx.org/r/proxy_intercept_errors
http://nginx.org/r/error_page
http://nginx.org/r/location
http://nginx.org/r/rewrite

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