Http2Session.streamIdleTimeout should permit being disabled from AbstractHTTP2ServerConnectionFactory

[niloc132]

Jetty version(s)
Jetty 11, including Jetty 11.0.15

Enhancement Description
Timeouts are configurable at several places when starting a Server, but the H2 streamIdleTimeout doesn't support being disabled without also disabling all timeouts on the same connector.

This isn't the typical H2 "keep-alive" timeout, but seems to be something specific to Jetty, allowing a server to prevent long-running streams.

HTTP2Session gets the value for streamIdleTimeout initially from Endpoint.getIdleTimeout(), which in turn gets the value from AbstractConnector.getIdleTimeout() - a general value that is used for effectively all timeouts.

It is also possible to set a more specific stream idle timeout on AbstractHTTP2ServerConnectionFactory's streamIdleTimeout property, but unfortunately any non-positive value will be ignored:
https://github.com/eclipse/jetty.project/blob/d1195b512340e9ab694fe5bb57b5615b437a475a/jetty-http2/http2-server/src/main/java/org/eclipse/jetty/http2/server/AbstractHTTP2ServerConnectionFactory.java#L268-L274

This makes it tricky to specify that other timeouts are acceptable in their default configuration, but long-running H2 streams to clients might be permitted to have longer delays between messages.

Workaround
As a workaround, it is possible to create a listener on the ServerConnector, and listen for HTTP2ServerConnection instances as they are created, and directly configure the session's timeout value.

        // Override the h2 stream timeout with a specified value
        serverConnector.addEventListener(new Connection.Listener() {
            @Override
            public void onOpened(Connection connection) {
                if (connection instanceof HTTP2ServerConnection) {
                    HTTP2Session session = (HTTP2Session) ((HTTP2Connection) connection).getSession();
                    session.setStreamIdleTimeout(0);// Disable timeout
                }
            }

            @Override
            public void onClosed(Connection connection) {

            }
        });

Related
Note that disabling stream idle timeouts appears to be another workaround for #8405, though that issue is about the client listening to a server stream, and even if the timeout isn't disabled, the stream will not stop after the timeout - instead, the bug will manifest, where onAllDataRead() is called twice, once before the server has finished sending.

Possible fix
It might be possible to simply remove the > 0 check in AbstractHTTP2ServerConnectionFactory.newConnection, either relaxing it to >= 0, or permitting negative values.

[sbordet]

@niloc132 would you be able to try #10173 and see if it fixes the issue for you?