Mastering Nginx

Reverse Proxy Advanced Topics

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Using this configuration, NGINX will set up a series of directories under /var/spool/

nginx that will first differentiate on the last character of the MD5 hash of the URI,
followed by the next two characters from the last. For example, the response for "/

this-is-a-typical-url" will be stored as:

/var/spool/nginx/3/f1/614c16873c96c9db2090134be91cbf13

In addition to the proxy_cache_valid directive, a number of headers control how

NGINX caches responses. The header values take precedence over the directive.

• The X-Accel-Expires header can be set by the upstream server to control
  cache behavior:

° An integer value indicates the time in seconds for which

a response may be cached

° If the value of this header is 0 , caching for that response

is disabled completely

• A value beginning with @ indicates the time in seconds since the epoch.
  The response is valid only up to this absolute time.


• The Expires and Cache-Control headers have the same precedence level.


• If the value of the Expires header is in the future, the response will be
  cached until then.


• The Cache-Control header can have multiple values:

° no-cache

° no-store

° private

° max-age

• The only value for which the response is actually cached is a max-age,
  which is numeric and non-zero, that is, max-age=x where x > 0.


• If the Set-Cookie header is present, the response is not cached.

This may be overridden, though, by using the proxy_ignore_headers

directive:

proxy_ignore_headers Set-Cookie;

• But if doing so, be sure to make the cookie value part of the proxy_cache_key:
  proxy_cache_key "$host$request_uri $cookie_user";