expires_in(seconds, options = {}) public

Sets an HTTP 1.1 Cache-Control header. Defaults to issuing a private instruction, so that intermediate caches must not cache the response.

expires_in 20.minutes
expires_in 3.hours, public: true
expires_in 3.hours, public: true, must_revalidate: true

This method will overwrite an existing Cache-Control header. See www.w3.org/Protocols/rfc2616/rfc2616-sec14.html for more possibilities.

HTTP Cache-Control Extensions for Stale Content. See tools.ietf.org/html/rfc5861 It helps to cache an asset and serve it while is being revalidated and/or returning with an error.

expires_in 3.hours, public: true, stale_while_revalidate: 60.seconds
expires_in 3.hours, public: true, stale_while_revalidate: 60.seconds, stale_if_error: 5.minutes

HTTP Cache-Control Extensions other values: developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control Any additional key-value pairs are concatenated onto the `Cache-Control` header in the response:

expires_in 3.hours, public: true, "s-maxage": 3.hours, "no-transform": true

The method will also ensure an HTTP Date header for client compatibility.

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April 10, 2013 - (v3.2.1 - v3.2.13)
2 thanks

be aware that this writes to tmp/cache

Its supposed to be http caching, but Rails will actually cache the response to whatever you specified as the cache store, *as well*, but only if you specify :public => true. The default is filestore so it will try to write to tmp/cache.

Only a problem if you don’t have the proper permissions set, in that scenario your apache/nginx logs could fill up very quickly with “permission denied errors”

Full explanation is here http://blog.tonycode.com/archives/418

May 8, 2015 - (>= v4.0.2)
0 thanks

This doesn't write files

This doesn’t write files, at least not anymore. Since at least rails 4 `Rack::Cache` isn’t included by default. In any case this method only ever set headers on the response.