feat(transport): Enable TCP_NODELAY. (#120)

The combination of the Nagle algorithm on a client, and delayed ack on a server
can introduce up to 200ms latency if a small gRPC messages is sent with multiple
writes.

Enable TCP_NODELAY to make sure that neither client, nor server buffer their
messages for too long when exchaning small requests.

tonic/src/transport/server.rs

@@ -427,7 +427,8 @@ struct TcpIncoming {
 
 impl TcpIncoming {
     fn bind(addr: SocketAddr) -> Result<Self, crate::Error> {
-        let inner = conn::AddrIncoming::bind(&addr).map_err(Box::new)?;
+        let mut inner = conn::AddrIncoming::bind(&addr).map_err(Box::new)?;
+        inner.set_nodelay(true);
 
         Ok(Self { inner })
     }

tonic/src/transport/service/connector.rs

@@ -13,6 +13,7 @@ use tower_service::Service;
 pub(crate) fn connector() -> HttpConnector {
     let mut http = HttpConnector::new();
     http.enforce_http(false);
+    http.set_nodelay(true);
     http
 }
 
@@ -32,6 +33,7 @@ impl Connector {
     pub(crate) fn new(tls: Option<TlsConnector>) -> Self {
         let mut http = HttpConnector::new();
         http.enforce_http(false);
+        http.set_nodelay(true);
 
         Self { http, tls }
     }