From 349f5e0846278edd17b167a64d70ac61eeb83203 Mon Sep 17 00:00:00 2001
From: behzad nouri <behzadnouri@gmail.com>
Date: Wed, 2 Aug 2023 21:54:45 +0000
Subject: [PATCH] read-locks Turbine QUIC connection cache for lookups (#32687)

Frequently accessed remote addresses are cached, making a shared-lock
sufficient which would reduce lock contention for the more common
cache-hit lookups.
---
 turbine/src/quic_endpoint.rs | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/turbine/src/quic_endpoint.rs b/turbine/src/quic_endpoint.rs
index 5568262d64..0f93391e04 100644
--- a/turbine/src/quic_endpoint.rs
+++ b/turbine/src/quic_endpoint.rs
@@ -294,8 +294,7 @@ async fn get_connection(
     sender: Sender<(Pubkey, SocketAddr, Bytes)>,
     cache: Arc<RwLock<ConnectionCache>>,
 ) -> Result<Connection, Error> {
-    let key = (remote_address, /*remote_pubkey:*/ None);
-    let entry = cache.write().await.entry(key).or_default().clone();
+    let entry = get_cache_entry(remote_address, &cache).await;
     {
         let connection: Option<Connection> = entry.read().await.clone();
         if let Some(connection) = connection {
@@ -342,6 +341,17 @@ fn get_remote_pubkey(connection: &Connection) -> Result<Pubkey, Error> {
     }
 }
 
+async fn get_cache_entry(
+    remote_address: SocketAddr,
+    cache: &RwLock<ConnectionCache>,
+) -> Arc<RwLock<Option<Connection>>> {
+    let key = (remote_address, /*remote_pubkey:*/ None);
+    if let Some(entry) = cache.read().await.get(&key) {
+        return entry.clone();
+    }
+    cache.write().await.entry(key).or_default().clone()
+}
+
 async fn cache_connection(
     remote_address: SocketAddr,
     remote_pubkey: Pubkey,