Adding a default cache-control header for routes served from FileAndResourceDirectives

[Prithvirajbilla]

FileAndResourceDirectives provides a lot of helpful functions to serve static assets from file system. Currently it adds Etag and Last-Modified response header to help with caching on browsers. I think we should also add a default Cache-Control response header. Because without a cache-control header, browsers are free to choose their own caching heuristic and that may result in serving stale assets from cache and some weird behaviours.

And, also I think the default cache-control header should be Cache-Control: must-revalidate, because this will trigger a cache revalidation on every request (If the requested asset is not changed, browser will get 304 - Not modified and served from cache)

Current workaround is to wrap getFromFile calls under respondWithHeader functions. It would be nice, if the library provides this to us by default.

[jrudolph]

Thanks for the suggestion, @Prithvirajbilla and sorry for the extremely long delay in answering.

Your suggestion seems quite reasonable. Do you have any resources about how serve static files in the best way?

[Prithvirajbilla]

Thanks for the response.

The default behavior I am proposing is the following. And, Let's see if agree on the default behavior.

• When a file is modified on server, browser must always get_ the latest file and must never use the file present in the cache.
• when a file is not modified on the server, browser must always use the cached file if present.

Proposed Solution Adding a default Cache-Control response header with value no-cache.

Please note that no-cache: doesn't mean "don't cache", but indicates that cache MUST NOT use a stored response to satisfy the request without successful validation on the origin server

Please note that the proposed solution in my earlier comment is not actually right, which I realized later on.

For more details, please look at the following resource. https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/http-caching#no-cache_and_no-store