HTTP/2 behind reverse proxy

Question

So far all the tutorials tell me that I need to enable SSL on my server to have HTTP/2 support.

In the given scenario, we have nginx in front of the backend Tomcat/J

Answer 1

You don't need to speak HTTP/2 all the way through.

HTTP/2 primarily addresses latency issues which will affect your client->Nginx connections. Server to server connections (e.g. Nginx to Tomcat/Jetty) will presumably be lower latency and therefore have less to gain from HTTP/2.

So just enable HTTPS and HTTP/2 on Nginx and then have it continue to talk HTTP/1.1 to Tomcat/Jetty.

There's also a question of whether everything supports HTTP/2 all the way through (e.g. Nginx proxy_pass directive and Tomcat/Jetty), which again is less of an issue if only using HTTP/2 at the edge of your network.