Align Server and Endpoint HTTP/2 keepalive setters (Option vs Duration)

Feature Request

Crates

• tonic (transport: Server + Endpoint)

Motivation

Server and Endpoint store the same kind of values internally (Option<Duration>), but the public setters disagree. Applying one config model to both sides currently requires two different call styles:

// Server: None disables HTTP/2 PING
Server::builder()
    .tcp_keepalive(tcp)                          // Option<Duration>
    .http2_keepalive_interval(interval)          // Option<Duration>
    .http2_keepalive_timeout(timeout)             // Option<Duration>
    .timeout(rpc_timeout);                     // Duration — omit the call to leave unset

// Endpoint: HTTP/2 PING has no None; skip the method to leave hyper's default
Channel::from_static("http://127.0.0.1:50051")
    .tcp_keepalive(tcp)                         // Option<Duration> (same as Server)
    .http2_keep_alive_interval(interval)        // Duration — cannot pass None
    .keep_alive_timeout(timeout)                // Duration
    .timeout(rpc_timeout);                    // Duration

This shows up whenever config uses 0 / missing = “do not set”. Server can take Option directly; the client must if let Some(d) { endpoint = endpoint.http2_keep_alive_interval(d); }.

Related inconsistency on the server setter itself: Server::http2_keepalive_timeout takes Option<Duration>, but None is a no-op and does not disable the default 20s timeout:

pub fn http2_keepalive_timeout(mut self, http2_keepalive_timeout: Option<Duration>) -> Self {
    if let Some(timeout) = http2_keepalive_timeout {
        self.http2_keepalive_timeout = timeout;
    }
    self
}

So even the Option API is not “None means off” for that method.

Proposal

Make the enable/disable story the same on both builders, for example:

1. Endpoint::http2_keep_alive_interval / keep_alive_timeout take Option<Duration> (None = leave hyper default / disable), matching Server::http2_keepalive_interval and tcp_keepalive.
2. Document timeout / connect_timeout as “call to set, omit to leave unset” (already Duration wrapping Some), or also accept Option if you want a single pattern everywhere.
3. Fix Server::http2_keepalive_timeout(None) so None either disables keepalive timeout or is documented as a no-op (today it looks like disable and is not).

A breaking change could wait for 0.15 with #[deprecated] aliases. A non-breaking path is adding *_opt methods or accepting impl Into<Option<Duration>> if that is acceptable.

Alternatives

• Keep the current APIs and document the Server vs Endpoint difference in the transport module docs.
• Only fix http2_keepalive_timeout(None) no-op, leave Endpoint as Duration.

I can send a PR if the preferred shape is clear.

Version

tonic 0.14.6