Apache – Set Header if It Doesn’t Already Exist

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 The cached versions will be served up to future clients until they are no longer valid (60 minutes).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;
    }
  }
}

I have answered my own question shortly after I posted by stumbling across a Stack Overflow question that I hadn't seen before. When using environment variables with a RewriteRule that does redirecting then Apache changes the name by prepending REDIRECT_ to the name.

Frustratingly enough, I was only doing a redirect for testing purposes and ultimately I just wanted to capture the parameters as headers so doing a RewriteRule ^/ - avoids the issue altogether.