Cache Headers

Query strings are a great way to brute force cache controls as the client - but the best way (assuming you have control of the server, and c'mon, we're backend devs), is to use the Cache-Control header. Some common values are:

• no-store: Don't cache this at all
• max-age=3600: Cache this for 1 hour (3600 seconds)
• stale-while-revalidate: Serve stale content while revalidating the cache
• no-cache: Does not mean "don't cache this". It means "cache this, but revalidate it before serving it again"

You can view all the other options here if you're interested.

When the server sends Cache-Control headers, it's up to the browser to respect them, but most modern browsers do.

Assignment

Let's do things the right way and control caching with headers from the server.

1. Edit app.js and revert it back to the way it was, just setting thumbnailImg.src = video.thumbnail_url; in the viewVideo function.
2. In cache.go rename the cacheMiddleware function to noCacheMiddleware (it will be more descriptive now)
3. Update the noCacheMiddleware function. It should set the Cache-Control header to no-store before handling the request.
4. Restart the application and hard refresh so the browser receives the new cache policy. Upload another thumbnail, then refresh normally to see it without client-side cache busting.

Run and submit the CLI tests.

Reassigning an image's existing src may not trigger a request, even with caching disabled. That's image loading behavior, not a failure of no-store.