testcluster: reduce ClusterName collisions

Epic: none
Release note: none

Author: pav-kv

pkg/testutils/testcluster/BUILD.bazel

@@ -38,6 +38,7 @@ go_library(
         "//pkg/util/allstacks",
         "//pkg/util/hlc",
         "//pkg/util/log",
+        "//pkg/util/randutil",
         "//pkg/util/retry",
         "//pkg/util/stop",
         "//pkg/util/syncutil",

pkg/testutils/testcluster/testcluster.go

@@ -9,7 +9,7 @@ import (
 	"context"
 	gosql "database/sql"
 	"fmt"
-	"math/rand/v2"
+	"math/rand"
 	"net"
 	"os"
 	"reflect"
@@ -51,6 +51,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/allstacks"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
+	"github.com/cockroachdb/cockroach/pkg/util/randutil"
 	"github.com/cockroachdb/cockroach/pkg/util/retry"
 	"github.com/cockroachdb/cockroach/pkg/util/stop"
 	"github.com/cockroachdb/cockroach/pkg/util/syncutil"
@@ -324,9 +325,14 @@ func NewTestCluster(
 		t.Fatal("StartSingleNode implies 1 node only, but asked to create", nodes)
 	}
 	if clusterArgs.ServerArgs.ClusterName == "" {
+		// NB: not using randutil.NewTestRand which deterministically depends on the
+		// testing seed. It would defeat the ClusterName's purpose (prevent messages
+		// across TestClusters), e.g. if a test is stressed with the same seed.
+		rng := rand.New(rand.NewSource(rand.Int63()))
 		// Use a cluster name that is sufficiently unique (within the CI env) but is
 		// concise and recognizable.
-		clusterArgs.ServerArgs.ClusterName = fmt.Sprintf("TestCluster-%d", rand.Uint32())
+		clusterArgs.ServerArgs.ClusterName = fmt.Sprintf("TestCluster-%s",
+			randutil.RandString(rng, 10, randutil.PrintableKeyAlphabet))
 	}
 
 	if err := checkServerArgsForCluster(