test: add TestRingSetAddrsContention

See https://github.com/go-redis/redis/pull/2190#discussion_r953040289

Updates #2077

ring_test.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"strconv"
 	"sync"
+	"testing"
 	"time"
 
 	. "github.com/onsi/ginkgo"
@@ -739,3 +740,88 @@ var _ = Describe("Ring Tx timeout", func() {
 		testTimeout()
 	})
 })
+
+func TestRingSetAddrsContention(t *testing.T) {
+	const (
+		ringShard1Name = "ringShardOne"
+		ringShard2Name = "ringShardTwo"
+	)
+
+	for _, port := range []string{ringShard1Port, ringShard2Port} {
+		if _, err := startRedis(port); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	t.Cleanup(func() {
+		for _, p := range processes {
+			if err := p.Close(); err != nil {
+				t.Errorf("Failed to stop redis process: %v", err)
+			}
+		}
+		processes = nil
+	})
+
+	ring := redis.NewRing(&redis.RingOptions{
+		Addrs: map[string]string{
+			"ringShardOne": ":" + ringShard1Port,
+		},
+		NewClient: func(opt *redis.Options) *redis.Client {
+			// Simulate slow shard creation
+			time.Sleep(100 * time.Millisecond)
+			return redis.NewClient(opt)
+		},
+	})
+
+	if _, err := ring.Ping(context.Background()).Result(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Continuously update addresses by adding and removing one address
+	updatesDone := make(chan struct{})
+	defer func() { close(updatesDone) }()
+	go func() {
+		ticker := time.NewTicker(10 * time.Millisecond)
+		defer ticker.Stop()
+		for i := 0; ; i++ {
+			select {
+			case <-ticker.C:
+				if i%2 == 0 {
+					ring.SetAddrs(map[string]string{
+						ringShard1Name: ":" + ringShard1Port,
+					})
+				} else {
+					ring.SetAddrs(map[string]string{
+						ringShard1Name: ":" + ringShard1Port,
+						ringShard2Name: ":" + ringShard2Port,
+					})
+				}
+			case <-updatesDone:
+				return
+			}
+		}
+	}()
+
+	var pings, errClosed int
+	timer := time.NewTimer(1 * time.Second)
+	for running := true; running; pings++ {
+		select {
+		case <-timer.C:
+			running = false
+		default:
+			if _, err := ring.Ping(context.Background()).Result(); err != nil {
+				if err == redis.ErrClosed {
+					// The shard client could be closed while ping command is in progress
+					errClosed++
+				} else {
+					t.Fatal(err)
+				}
+			}
+		}
+	}
+
+	t.Logf("Number of pings: %d, errClosed: %d", pings, errClosed)
+	if pings < 10_000 {
+		t.Errorf("Expected at least 10k pings, got: %d", pings)
+	}
+}