send_file (ActionController::Streaming) - APIdock

send_file (ActionController::Streaming) - APIdock:

Also be aware that the document may be cached by proxies and browsers. The Pragma and Cache-Control headers declare how the file may be cached by intermediaries. They default to require clients to validate with the server before releasing cached responses. See http://www.mnot.net/cache_docs/ for an overview of web caching and http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9 for the Cache-Control header spec.

Full article: http://apidock.com/rails/ActionController/Streaming/send_...