From c366649516dcd1d780ca8b7938397dac61338c15 Mon Sep 17 00:00:00 2001
From: Rob Ede <robjtede@icloud.com>
Date: Fri, 7 Jun 2024 16:57:03 +0100
Subject: [PATCH] docs: example of CPU core pinning

---
 actix-web/Cargo.toml                 |  2 +-
 actix-web/examples/worker-cpu-pin.rs | 41 ++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 actix-web/examples/worker-cpu-pin.rs

diff --git a/actix-web/Cargo.toml b/actix-web/Cargo.toml
index 9f3ab6e5e..a666f14be 100644
--- a/actix-web/Cargo.toml
+++ b/actix-web/Cargo.toml
@@ -35,7 +35,6 @@ features = [
     "secure-cookies",
 ]
 
-
 [lib]
 name = "actix_web"
 path = "src/lib.rs"
@@ -130,6 +129,7 @@ awc = { version = "3", features = ["openssl"] }
 
 brotli = "6"
 const-str = "0.5"
+core_affinity = "0.8"
 criterion = { version = "0.5", features = ["html_reports"] }
 env_logger = "0.11"
 flate2 = "1.0.13"
diff --git a/actix-web/examples/worker-cpu-pin.rs b/actix-web/examples/worker-cpu-pin.rs
new file mode 100644
index 000000000..58e060821
--- /dev/null
+++ b/actix-web/examples/worker-cpu-pin.rs
@@ -0,0 +1,41 @@
+use std::{
+    io,
+    sync::{
+        atomic::{AtomicUsize, Ordering},
+        Arc,
+    },
+    thread,
+};
+
+use actix_web::{middleware, web, App, HttpServer};
+
+async fn hello() -> &'static str {
+    "Hello world!"
+}
+
+#[actix_web::main]
+async fn main() -> io::Result<()> {
+    env_logger::init_from_env(env_logger::Env::new().default_filter_or("info"));
+
+    let core_ids = core_affinity::get_core_ids().unwrap();
+    let n_core_ids = core_ids.len();
+    let next_core_id = Arc::new(AtomicUsize::new(0));
+
+    HttpServer::new(move || {
+        let pin = Arc::clone(&next_core_id).fetch_add(1, Ordering::AcqRel);
+        log::info!(
+            "setting CPU affinity for worker {}: pinning to core {}",
+            thread::current().name().unwrap(),
+            pin,
+        );
+        core_affinity::set_for_current(core_ids[pin]);
+
+        App::new()
+            .wrap(middleware::Logger::default())
+            .service(web::resource("/").get(hello))
+    })
+    .bind(("127.0.0.1", 8080))?
+    .workers(n_core_ids)
+    .run()
+    .await
+}