Hi, On Mon, 26 Feb 2024 01:34:31 +0300 Maxim Dounin <mdou...@mdounin.ru> wrote:
> [...] > As far as I understand, the Critical-CH header should be good > enough for most use cases, except might be for statistical > counters which often use just one HTTP request, and therefore > another one will be a huge change. > > If you are able to share, it would be great if you'll provide more > details about your use case. A very simple use case is basic contextual ads. Presenting a somewhat targeted ad with no user information, no session cookie, nothing more than what a single http request provides. This means using in real time things like the referer header, the accepted languages and the user-agent string. The Mobile and Platform UA-CH headers do still provide the most critical information for this, so it's more about the corner cases: If an Android app is only compatible with Android 10 and up, you don't want to be advertising to users of Android 9 and below. Delivering such a targeted ad currently requires only one http request. But with a reduced User-Agent and the Platform-Version CH header missing, it's no longer possible. What can be tried is: * Replying with the Critical-CH header. The client might then re-request an ad... or not, which will skew things quite a bit. * Redirect the client in order to request the header. You expose yourself to potential infinite redirection bugs and use more resources because of the extra http request. > > So it seems like as of right now, with recent Chrome & Edge clients, > > there is no way to have nginx receive more than the 3 default client > > hints during the first client http connection? > > Yes, there is no support now (except the patch you've mentioned). I *really* wanted to avoid having to dig that patch up and potentially have to switch TLS library just to make this work! :-) I also wanted to avoid having to implement a redirection in nginx, but I think I will have to also try something like this out in case it does end up working reliably: * If our parameter indicating we already redirected is missing, * And the UA-CH Mobile header is present, * And the UA-CH Platform-Version header is absent, * Then redirect to the same URL but appending our parameter indicating we already redirected. This way it could potentially still achieve triggering a single request to the backend nginx is using, that would include the Platform-Version if the client agreed to provide it. Cheers, Matthias -- nginx mailing list nginx@freenginx.org https://freenginx.org/mailman/listinfo/nginx
