2

I want to change the cache control header when there's an HTTP redirect related code (30x).

How can I check the response's HTTP code to see if I should run add_header

  • 1
    Great question! I'm amazed it got so little attention! – cnst Aug 28 '17 at 1:08
1

The following should work:

server {
    listen 60729;
    error_page 301 @301;
    return 301 http://example.su/test;
    location @301 {
        add_header X-Header value;
        return 301 $sent_http_location;
    }
}

Here's the confirmation:

%curl -v localhost:60729 | & fgrep \
    -e HTTP/ -e X-Header -e Location -e title | sed 's#^#\t#g'
> GET / HTTP/1.1
< HTTP/1.1 301 Moved Permanently
< Location: http://example.su/test
< X-Header: value
<head><title>301 Moved Permanently</title></head>

Note that each part of the config is quite important:

  • the error_page directive effectively provides a very neat exception handling capabilities to nginx;

  • without return 301 within location @301, nginx will try to serve the requisite file from the filesystem; this will likely result in a 404, so, you'll get a 404 page; note that the Location header would still be preserved, but the X-Header will be missing from a 404 Not Found page, because, as per the documentation of the add_header directive, it doesn't let you add headers to error pages;

  • with a plain return 301; within location @301, you will effectively clear out the Location, so, your Location would be empty; thus you have to use $sent_http_ to preserve the current value.

If you want to try out my POC MVP as above, you can find the full config in my GitHub at https://github.com/cnst/StackOverflow.cnst.nginx.conf.

-1

This should work if you're doing the redirects within nginx. You'll have to build Nginx with the headers_more module which is pretty easy - see my Nginx tutorial here.

 location /match/ {
   add_header HEADER_NAME "header value";
   return 301 https://example.com;
 }

If you're proxying through to an application that's returning redirects then it would be a little more complex, probably involving IF statements. IF in nginx doesn't always work as you expect, so you may be best off changing the application in that case.

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