MAX_CONNECTION_AGE_GRACE not really implemented

[ejona86]

#9649 implemented MAX_CONNECTION_AGE and claims to implement the grace period as well, but it doesn't really. The shutdown code normally uses 1s as a limit during GOAWAY. That's actually fine as-is for MAX_CONNECTION_AGE. Most of the time that limit won't matter; most of the time the client will respond with a PING before it expires and we'll then promptly send the second GOAWAY.

What is missing is we should set a graceful timer to close the connection. That could either be an abrupt closure, but I think in Netty we trigger RST_STREAM all the streams and then the normal 'the connection is shutdown and there are no more streams' logic can naturally close the connection.

[YifeiZhuang]

There is no RST_STREAM sent in the GracefulShutdown in grpc-netty.

There is RST_STREAM sent in shutdownNow in netty, and okhttp.

OkHttp will send two consecutive goAway(). Then wait MAX_CONNECTION_AGE_GRACE and close abruptly (a graceful shutdown similar to grpc-netty).

rfc7540#section-6.4