When specifying public Cache-Control, also specify max-age

The ActionController stale? and fresh_when functions will take a :public option, which will cause emission of a Cache-Control header with a public attribute.

Proxy caches will likely interpret a "Cache-Control: public" header to mean that the resource will never change, and will cache it forever.

If you're using either stale? or fresh_when, it's probably because the controlled resource does change over time, so you want to specify a max-age directive in the Cache-Control header to tell the proxy cache how long to serve the resource before asking the origin if it's changed.

Use of expires_in does set the max-age, and it is a workaround for this problem, but it feels awkward to have to do both.

Adding a :max_age option to fresh_when would deal with this nicely