mod_expire

mod_expire add "Expires" and "Cache-Control" headers to the response

This allows you to control client-side caching of responses based on a simple rule/formula.
If a response is cached using an “Expires” and “Cache-Control” header, then the client will not issue a new request for it until the date specified by the header is reached.

Adding expire headers to static content like css, javascript, images or similar, can greatly reduce the amount of requests you get and therefor save resources.
Use “modification” as <base> if your content changes in specific intervals like every 15 minutes.

expire (action)

adds an "Expires" header to the response

expire rule;

rule: the rule to calculate the "Expires" header value with

The rule/formula used here, complies with the one mod_expire for Apache uses:

<base> [plus] (<num> <type>)+

<base> is one of “access”, “now” or “modification”; “now” being equivalent to “access”.
“plus” is optional and does nothing.
<num> is any positive integer.
<type> is one of “seconds”, “minutes”, “hours”, “days”, “weeks”, “months” or “years”.

The trailing “s” in <type> is optional.

If you use “modification” as <base> and the file does not exist or cannot be accessed, mod_expire will do nothing and request processing will go on.

The expire action will overwrite any existing “Expires” header.
It will append the max-age value to any existing “Cache-Control” header.

Example

Cache image, css, txt and js files for 1 week.

setup {
	module_load "mod_expire";
}

if req.path =~ "\.(jpe?g|png|gif|txt|css|js)$" {
	expire "access plus 1 week";
}