Simplifying serve function (#5902)

In particular, there is no need to parse TLS config
upon the reception of every connections.

Co-authored-by: fulmicoton <paul.masurel@datadoghq.com>

Author: fulmicoton

quickwit/quickwit-serve/src/rest.rs

@@ -13,6 +13,7 @@
 // limitations under the License.
 
 use std::fmt::Formatter;
+use std::io;
 use std::sync::Arc;
 
 use hyper_util::rt::{TokioExecutor, TokioIo};
@@ -21,7 +22,8 @@ use hyper_util::service::TowerToHyperService;
 use quickwit_common::tower::BoxFutureInfaillible;
 use quickwit_config::{disable_ingest_v1, enable_ingest_v2};
 use quickwit_search::SearchService;
-use tokio::net::TcpListener;
+use tokio::io::{AsyncRead, AsyncWrite};
+use tokio::net::{TcpListener, TcpStream};
 use tokio_rustls::TlsAcceptor;
 use tokio_util::either::Either;
 use tower::ServiceBuilder;
@@ -120,6 +122,20 @@ impl Predicate for CompressionPredicate {
     }
 }
 
+async fn apply_tls_if_necessary(
+    tcp_stream: TcpStream,
+    tls_acceptor_opt: &Option<TlsAcceptor>,
+) -> io::Result<impl AsyncRead + AsyncWrite + Unpin + 'static> {
+    let Some(tls_acceptor) = &tls_acceptor_opt else {
+        return Ok(Either::Right(tcp_stream));
+    };
+    let tls_stream_res = tls_acceptor
+        .accept(tcp_stream)
+        .await
+        .inspect_err(|err| error!("failed to perform tls handshake: {err:#}"))?;
+    Ok(Either::Left(tls_stream_res))
+}
+
 /// Starts REST services.
 pub(crate) async fn start_rest_server(
     tcp_listener: TcpListener,
@@ -227,37 +243,33 @@ pub(crate) async fn start_rest_server(
     let mut shutdown_signal = std::pin::pin!(shutdown_signal);
     readiness_trigger.await;
 
+    let tls_acceptor_opt: Option<TlsAcceptor> =
+        if let Some(tls_config) = &quickwit_services.node_config.rest_config.tls {
+            let rustls_config = tls::make_rustls_config(tls_config)?;
+            Some(TlsAcceptor::from(rustls_config))
+        } else {
+            None
+        };
+
     loop {
         tokio::select! {
-            conn = tcp_listener.accept() => {
-                let (stream, _remote_addr) = match conn {
-                    Ok(conn) => conn,
+            tcp_accept_res = tcp_listener.accept() => {
+                let tcp_stream = match tcp_accept_res {
+                    Ok((tcp_stream, _remote_addr)) => tcp_stream,
                     Err(err) => {
                         error!("failed to accept connection: {err:#}");
                         continue;
                     }
                 };
 
-                let either_stream =
-                if let Some(tls_config) = &quickwit_services.node_config.rest_config.tls {
-                    let rustls_config = tls::make_rustls_config(tls_config)?;
-                    let acceptor = TlsAcceptor::from(rustls_config);
-                    let tls_stream = match acceptor.accept(stream).await {
-                        Ok(tls_stream) => tls_stream,
-                        Err(err) => {
-                            error!("failed to perform tls handshake: {err:#}");
-                            continue;
-                        }
-                    };
-                    Either::Left(tls_stream)
-                } else {
-                    Either::Right(stream)
+                let Ok(tcp_or_tls_stream) = apply_tls_if_necessary(tcp_stream, &tls_acceptor_opt).await else {
+                    continue;
                 };
 
-                let conn = server.serve_connection_with_upgrades(TokioIo::new(either_stream), service.clone());
-                let conn = graceful.watch(conn.into_owned());
+                let serve_fut = server.serve_connection_with_upgrades(TokioIo::new(tcp_or_tls_stream), service.clone());
+                let serve_with_shutdown_fut = graceful.watch(serve_fut.into_owned());
                 tokio::spawn(async move {
-                    if let Err(err) = conn.await {
+                    if let Err(err) = serve_with_shutdown_fut.await {
                         error!("failed to serve connection: {err:#}");
                     }
                 });
@@ -269,11 +281,8 @@ pub(crate) async fn start_rest_server(
         }
     }
 
-    tokio::select! {
-        _ = graceful.shutdown() => {
-            info!("gracefully shutdown");
-        }
-    }
+    graceful.shutdown().await;
+    info!("gracefully shutdown");
 
     Ok(())
 }