Nginx Reverse Proxy – Forward Custom Header

nginxreverse-proxy

I have an nginx web server acting as a reverse proxy to forward requests on to Apache for additional handling (I'm begging you not to ask why). I have a request to which I'm trying to attach a custom header and I'd like for nginx to forward that custom header along to Apache so I can do something with it in an app.

I've poked through the HttpProxyModule docs, but they're not very descriptive even if I'm in the right place (it very well could be that I'm not).

How can I get nginx to forward an X-CUSTOM-REFERRER header? Moreover, if possible, I'd like it to forward along any custom header that comes in. If the latter is too much to ask, the former would suffice for my current need.

As you can see, I'm very new to nginx, so the remedial version would be helpful.

Thanks.

UPDATE

The relevant snippet from my existing config:

location / {
    proxy_pass                  http://preview;
    proxy_redirect              off;
    proxy_set_header            Host $host;
    proxy_set_header            X-Real-IP $remote_addr;
    proxy_set_header            X-Forwarded-For $proxy_add_x_forwarded_for;
    # proxy_set_header            X-Custom-Referrer $x_custom_referrer;
}

Best Answer

The proxy_set_header directive from the HttpProxyModule allows you to do this. For example:

proxy_pass http://apachehost;
proxy_set_header X-Custom-Referrer $proxy_add_<header_field_name_from_last_request>;

Related Solutions

Nginx – How to Set Up as a Caching Reverse Proxy

I don't think that there is a way to explicitly invalidate cached items, but here is an example of how to do the rest. Update: As mentioned by Piotr in another answer, there is a cache purge module that you can use. You can also force a refresh of a cached item using nginx's proxy_cache_bypass - see Cherian's answer for more information.

In this configuration, items that aren't cached will be retrieved from example.net and stored. The cached versions will be served up to future clients until they are no longer valid (60 minutes).

Your Cache-Control and Expires HTTP headers will be honored, so if you want to explicitly set an expiration date, you can do that by setting the correct headers in whatever you are proxying to.

There are lots of parameters that you can tune - see the nginx Proxy module documentation for more information about all of this including details on the meaning of the different settings/parameters: http://nginx.org/r/proxy_cache_path

http {
  proxy_cache_path  /var/www/cache levels=1:2 keys_zone=my-cache:8m max_size=1000m inactive=600m;
  proxy_temp_path /var/www/cache/tmp; 


  server {
    location / {
      proxy_pass http://example.net;
      proxy_cache my-cache;
      proxy_cache_valid  200 302  60m;
      proxy_cache_valid  404      1m;
    }
  }
}

Nginx reverse proxy: Not setting expires header

Nginx only ever applies one location, never more. In your example it will apply the expires header to existing static files, but any files not found and thus coming from the @upstream location will ignore access_log, expires and add_header directives from static location.

If you want to set expires you should duplicate the directive across both locations. Setting proxy_hide_header might also be required.

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