From 869e515ea8acc1e7abc90f3c50a539bc88fbf6b4 Mon Sep 17 00:00:00 2001
From: Michael Lumish <mlumish@google.com>
Date: Fri, 18 Jul 2025 11:23:48 -0700
Subject: [PATCH] grpc-js: round_robin: Start connecting to endpoints from a
 random index

---
 packages/grpc-js/src/load-balancer-round-robin.ts | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/packages/grpc-js/src/load-balancer-round-robin.ts b/packages/grpc-js/src/load-balancer-round-robin.ts
index 15a071c8..17756b41 100644
--- a/packages/grpc-js/src/load-balancer-round-robin.ts
+++ b/packages/grpc-js/src/load-balancer-round-robin.ts
@@ -90,6 +90,10 @@ class RoundRobinPicker implements Picker {
   }
 }
 
+function rotateArray<T>(list: T[], startIndex: number) {
+  return [...list.slice(startIndex), ...list.slice(0, startIndex)];
+}
+
 export class RoundRobinLoadBalancer implements LoadBalancer {
   private children: LeafLoadBalancer[] = [];
 
@@ -228,7 +232,8 @@ export class RoundRobinLoadBalancer implements LoadBalancer {
       }
       return true;
     }
-    const endpointList = maybeEndpointList.value;
+    const startIndex = (Math.random() * maybeEndpointList.value.length) | 0;
+    const endpointList = rotateArray(maybeEndpointList.value, startIndex);
     this.resetSubchannelList();
     if (endpointList.length === 0) {
       const errorMessage = `No addresses resolved. Resolution note: ${resolutionNote}`;