From d7ba255394435f444ec274b49c8464eac1cb3568 Mon Sep 17 00:00:00 2001
From: ofekshenawa <104765379+ofekshenawa@users.noreply.github.com>
Date: Wed, 21 May 2025 13:58:21 +0300
Subject: [PATCH] fix: prevent routing reads to loading slave nodes (#3370)

Co-authored-by: Nedyalko Dyakov <1547186+ndyakov@users.noreply.github.com>
---
 osscluster.go | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/osscluster.go b/osscluster.go
index 2365f771..cc2444fa 100644
--- a/osscluster.go
+++ b/osscluster.go
@@ -445,6 +445,14 @@ func (n *clusterNode) SetLastLatencyMeasurement(t time.Time) {
 	}
 }
 
+func (n *clusterNode) Loading() bool {
+	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	defer cancel()
+
+	err := n.Client.Ping(ctx).Err()
+	return err != nil && isLoadingError(err)
+}
+
 //------------------------------------------------------------------------------
 
 type clusterNodes struct {
@@ -754,7 +762,8 @@ func (c *clusterState) slotSlaveNode(slot int) (*clusterNode, error) {
 	case 1:
 		return nodes[0], nil
 	case 2:
-		if slave := nodes[1]; !slave.Failing() {
+		slave := nodes[1]
+		if !slave.Failing() && !slave.Loading() {
 			return slave, nil
 		}
 		return nodes[0], nil
@@ -763,7 +772,7 @@ func (c *clusterState) slotSlaveNode(slot int) (*clusterNode, error) {
 		for i := 0; i < 10; i++ {
 			n := rand.Intn(len(nodes)-1) + 1
 			slave = nodes[n]
-			if !slave.Failing() {
+			if !slave.Failing() && !slave.Loading() {
 				return slave, nil
 			}
 		}