I am implementing an HTTP polling mechanism to detect device network status. I am planning to make a periodic GET request to a static file /static/byte.txt to validate the device's internet access.

I am using the Cache-Control: no-cache request header to make sure I am not served with a cached copy of the file on the device (which defeats the purpose). But I would like to still use any cached copy of the file on the CDN, as there is no need to download the file from the origin (my servers) every time. Does anyone know of a way to set the cache control headers to achieve that? Thanks!

CodePudding user response：

The Cache-Control request header is a poor fit for this use case as both the client HTTP library and the CDN will assign the same meaning to whatever cache control directive you choose.

Instead, I recommend using a Cache-Control response header. In the response, you can use something like Cache-Control: max-age=0, s-maxage=604800, which indicates that the client should not cache the response but the CDN can cache it for up to a week (604,800 seconds).