From 702b274ebfdb2952fdf2e0ef4c70c02817766a02 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=93=9D=E5=AE=9D=E7=9F=B3=E7=9A=84=E5=82=BB=E8=AF=9D?=
 <mickey_zzc@163.com>
Date: Mon, 10 Apr 2023 16:03:36 +0800
Subject: [PATCH 1/2] truncateExtLabels support Unicode cut

Signed-off-by: mickeyzzc <mickey_zzc@163.com>
---
 pkg/query/endpointset.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/pkg/query/endpointset.go b/pkg/query/endpointset.go
index 36f6d389fe..dfd3ec8390 100644
--- a/pkg/query/endpointset.go
+++ b/pkg/query/endpointset.go
@@ -11,6 +11,7 @@ import (
 	"sort"
 	"sync"
 	"time"
+	"unicode/utf8"
 
 	"github.com/thanos-io/thanos/pkg/api/query/querypb"
 
@@ -218,7 +219,13 @@ func newEndpointSetNodeCollector(labels ...string) *endpointSetNodeCollector {
 // truncateExtLabels truncates the stringify external labels with the format of {labels..}.
 func truncateExtLabels(s string, threshold int) string {
 	if len(s) > threshold {
-		return fmt.Sprintf("%s}", s[:threshold-1])
+		for cut := 1; cut < 4; cut++ {
+			for cap := 1; cap < 4; cap++ {
+				if utf8.ValidString(s[threshold-cut-cap : threshold-cut]) {
+					return fmt.Sprintf("%s}", s[:threshold-cut])
+				}
+			}
+		}
 	}
 	return s
 }

From 307b8e442d481b7fc3033dc5f1aecece4b2ac921 Mon Sep 17 00:00:00 2001
From: mickeyzzc <mickey_zzc@163.com>
Date: Tue, 11 Apr 2023 12:47:08 +0800
Subject: [PATCH 2/2] update TestTruncateExtLabels and pass test

Signed-off-by: mickeyzzc <mickey_zzc@163.com>
---
 pkg/query/endpointset_test.go | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/pkg/query/endpointset_test.go b/pkg/query/endpointset_test.go
index 2edfe01718..70b95c8ab5 100644
--- a/pkg/query/endpointset_test.go
+++ b/pkg/query/endpointset_test.go
@@ -272,7 +272,7 @@ func (e *testEndpoints) CloseOne(addr string) {
 }
 
 func TestTruncateExtLabels(t *testing.T) {
-	const testLength = 5
+	const testLength = 10
 
 	for _, tc := range []struct {
 		labelToTruncate string
@@ -283,20 +283,24 @@ func TestTruncateExtLabels(t *testing.T) {
 			expectedOutput:  "{abc}",
 		},
 		{
-			labelToTruncate: "{abcd}",
-			expectedOutput:  "{abc}",
+			labelToTruncate: "{abcdefgh}",
+			expectedOutput:  "{abcdefgh}",
 		},
 		{
-			labelToTruncate: "{abcde}",
-			expectedOutput:  "{abc}",
+			labelToTruncate: "{abcdefghij}",
+			expectedOutput:  "{abcdefgh}",
 		},
 		{
-			labelToTruncate: "{abcdef}",
-			expectedOutput:  "{abc}",
+			labelToTruncate: "{abcde花}",
+			expectedOutput:  "{abcde花}",
 		},
 		{
-			labelToTruncate: "{abcdefghij}",
-			expectedOutput:  "{abc}",
+			labelToTruncate: "{abcde花朵}",
+			expectedOutput:  "{abcde花}",
+		},
+		{
+			labelToTruncate: "{abcde花fghij}",
+			expectedOutput:  "{abcde花}",
 		},
 	} {
 		t.Run(tc.labelToTruncate, func(t *testing.T) {