From 63792327776ade657bdd4c73f5aa8d0d6f88e4ad Mon Sep 17 00:00:00 2001
From: David Pedersen <david.pdrsn@gmail.com>
Date: Sat, 2 Dec 2023 14:34:53 +0100
Subject: [PATCH 1/2] Gracefully handle accept errors in `serve`

---
 axum/CHANGELOG.md  |  2 ++
 axum/src/macros.rs | 12 ++++++++++++
 axum/src/serve.rs  | 36 +++++++++++++++++++++++++++++++++++-
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/axum/CHANGELOG.md b/axum/CHANGELOG.md
index 4012f6034d..bf7321766a 100644
--- a/axum/CHANGELOG.md
+++ b/axum/CHANGELOG.md
@@ -8,8 +8,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 # Unreleased
 
 - **added:** Add `axum::body::to_bytes` ([#2373])
+- **fixed:** Gracefully handle accept errors in `serve` ([#2400])
 
 [#2373]: https://github.com/tokio-rs/axum/pull/2373
+[#2400]: https://github.com/tokio-rs/axum/pull/2400
 
 # 0.7.1 (27. November, 2023)
 
diff --git a/axum/src/macros.rs b/axum/src/macros.rs
index 180c3c05a5..7024f77998 100644
--- a/axum/src/macros.rs
+++ b/axum/src/macros.rs
@@ -66,3 +66,15 @@ macro_rules! all_the_tuples {
         $name!([T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15], T16);
     };
 }
+
+#[cfg(feature = "tracing")]
+macro_rules! error {
+    ($($tt:tt)*) => {
+        tracing::error!($($tt)*)
+    };
+}
+
+#[cfg(not(feature = "tracing"))]
+macro_rules! error {
+    ($($tt:tt)*) => {};
+}
diff --git a/axum/src/serve.rs b/axum/src/serve.rs
index c6aa2784c8..4e9c1d17da 100644
--- a/axum/src/serve.rs
+++ b/axum/src/serve.rs
@@ -8,6 +8,7 @@ use std::{
     net::SocketAddr,
     pin::Pin,
     task::{Context, Poll},
+    time::Duration,
 };
 
 use axum_core::{body::Body, extract::Request, response::Response};
@@ -147,7 +148,31 @@ where
             } = self;
 
             loop {
-                let (tcp_stream, remote_addr) = tcp_listener.accept().await?;
+                let (tcp_stream, remote_addr) = match tcp_listener.accept().await {
+                    Ok(conn) => conn,
+                    Err(e) => {
+                        // Connection errors can be ignored directly, continue
+                        // by accepting the next request.
+                        if is_connection_error(&e) {
+                            continue;
+                        }
+
+                        // [From `hyper::Server` in 0.14](https://github.com/hyperium/hyper/blob/v0.14.27/src/server/tcp.rs#L186)
+                        //
+                        // > A possible scenario is that the process has hit the max open files
+                        // > allowed, and so trying to accept a new connection will fail with
+                        // > `EMFILE`. In some cases, it's preferable to just wait for some time, if
+                        // > the application will likely close some files (or connections), and try
+                        // > to accept the connection again. If this option is `true`, the error
+                        // > will be logged at the `error` level, since it is still a big deal,
+                        // > and then the listener will sleep for 1 second.
+                        //
+                        // hyper allowed customizing this but axum does not.
+                        error!("accept error: {}", e);
+                        tokio::time::sleep(Duration::from_secs(1)).await;
+                        continue;
+                    }
+                };
                 let tcp_stream = TokioIo::new(tcp_stream);
 
                 poll_fn(|cx| make_service.poll_ready(cx))
@@ -187,6 +212,15 @@ where
     }
 }
 
+fn is_connection_error(e: &io::Error) -> bool {
+    matches!(
+        e.kind(),
+        io::ErrorKind::ConnectionRefused
+            | io::ErrorKind::ConnectionAborted
+            | io::ErrorKind::ConnectionReset
+    )
+}
+
 mod private {
     use std::{
         future::Future,

From f5d36ad606bbda1adc4c13dbe93cd5b538c4f522 Mon Sep 17 00:00:00 2001
From: David Pedersen <david.pdrsn@gmail.com>
Date: Sat, 2 Dec 2023 19:00:53 +0100
Subject: [PATCH 2/2] Update axum/src/serve.rs

Co-authored-by: Jonas Platte <jplatte+git@posteo.de>
---
 axum/src/serve.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/axum/src/serve.rs b/axum/src/serve.rs
index 4e9c1d17da..f9b48c41e2 100644
--- a/axum/src/serve.rs
+++ b/axum/src/serve.rs
@@ -168,7 +168,7 @@ where
                         // > and then the listener will sleep for 1 second.
                         //
                         // hyper allowed customizing this but axum does not.
-                        error!("accept error: {}", e);
+                        error!("accept error: {e}");
                         tokio::time::sleep(Duration::from_secs(1)).await;
                         continue;
                     }