From 62fc2c821b7b9d757a5dee74a4c17e0010c8301e Mon Sep 17 00:00:00 2001
From: Anatoly Rugalev <anatoly.rugalev@gmail.com>
Date: Sat, 17 Jul 2021 18:20:48 +0200
Subject: [PATCH] Check Failing() before serving random node (#1825)

* Check Failing() before serving random node

* Revert condition

* Addressed review comments

* Fallback to random failing node
---
 cluster.go | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/cluster.go b/cluster.go
index 9690f88a..8d93b369 100644
--- a/cluster.go
+++ b/cluster.go
@@ -595,8 +595,16 @@ func (c *clusterState) slotRandomNode(slot int) (*clusterNode, error) {
 	if len(nodes) == 0 {
 		return c.nodes.Random()
 	}
-	n := rand.Intn(len(nodes))
-	return nodes[n], nil
+	if len(nodes) == 1 {
+		return nodes[0], nil
+	}
+	randomNodes := rand.Perm(len(nodes))
+	for _, idx := range randomNodes {
+		if node := nodes[idx]; !node.Failing() {
+			return node, nil
+		}
+	}
+	return nodes[randomNodes[0]], nil
 }
 
 func (c *clusterState) slotNodes(slot int) []*clusterNode {