lightning: fix lightning failed to log encoding error

br/pkg/lightning/backend/kv/BUILD.bazel

@@ -48,6 +48,7 @@ go_test(
     name = "kv_test",
     timeout = "short",
     srcs = [
+        "base_test.go",
         "kv2sql_test.go",
         "session_internal_test.go",
         "session_test.go",
@@ -56,7 +57,7 @@ go_test(
     embed = [":kv"],
     flaky = True,
     race = "on",
-    shard_count = 18,
+    shard_count = 19,
     deps = [
         "//br/pkg/lightning/backend/encode",
         "//br/pkg/lightning/common",

br/pkg/lightning/backend/kv/base.go

@@ -77,6 +77,7 @@ var kindStr = [...]string{
 
 // MarshalLogArray implements the zapcore.ArrayMarshaler interface
 func (row RowArrayMarshaller) MarshalLogArray(encoder zapcore.ArrayEncoder) error {
+	var totalLength = 0
 	for _, datum := range row {
 		kind := datum.Kind()
 		var str string
@@ -94,6 +95,14 @@ func (row RowArrayMarshaller) MarshalLogArray(encoder zapcore.ArrayEncoder) erro
 				return err
 			}
 		}
+		if len(str) > 512*1024 {
+			str = str[0:1024] + " (truncated)"
+		}
+		totalLength += len(str)
+		if totalLength >= 512*1024 {
+			encoder.AppendString("The row has been truncated, and the log has exited early.")
+			return nil
+		}
 		if err := encoder.AppendObject(zapcore.ObjectMarshalerFunc(func(enc zapcore.ObjectEncoder) error {
 			enc.AddString("kind", kindStr[kind])
 			enc.AddString("val", redact.String(str))
@@ -307,9 +316,16 @@ func (e *BaseKVEncoder) LogKVConvertFailed(row []types.Datum, j int, colInfo *mo
 		log.ShortError(err),
 	)
 
-	e.logger.Error("failed to convert kv value", logutil.RedactAny("origVal", original.GetValue()),
-		zap.Stringer("fieldType", &colInfo.FieldType), zap.String("column", colInfo.Name.O),
-		zap.Int("columnID", j+1))
+	if len(original.GetString()) >= 512*1024 {
+		originalPrefix := original.GetString()[0:1024] + " (truncated)"
+		e.logger.Error("failed to convert kv value", logutil.RedactAny("origVal", originalPrefix),
+			zap.Stringer("fieldType", &colInfo.FieldType), zap.String("column", colInfo.Name.O),
+			zap.Int("columnID", j+1))
+	} else {
+		e.logger.Error("failed to convert kv value", logutil.RedactAny("origVal", original.GetValue()),
+			zap.Stringer("fieldType", &colInfo.FieldType), zap.String("column", colInfo.Name.O),
+			zap.Int("columnID", j+1))
+	}
 	return errors.Annotatef(
 		err,
 		"failed to cast value as %s for column `%s` (#%d)", &colInfo.FieldType, colInfo.Name.O, j+1,

br/pkg/lightning/backend/kv/base_test.go

@@ -0,0 +1,75 @@
+// Copyright 2023 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package kv
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/pingcap/tidb/br/pkg/lightning/backend/encode"
+	"github.com/pingcap/tidb/br/pkg/lightning/log"
+	"github.com/pingcap/tidb/parser/model"
+	"github.com/pingcap/tidb/parser/mysql"
+	"github.com/pingcap/tidb/table"
+	"github.com/pingcap/tidb/table/tables"
+	"github.com/pingcap/tidb/types"
+	"github.com/stretchr/testify/require"
+)
+
+func TestLogKVConvertFailed(t *testing.T) {
+	tempPath := filepath.Join(t.TempDir(), "/temp.txt")
+	logCfg := &log.Config{File: tempPath, FileMaxSize: 1}
+	err := log.InitLogger(logCfg, "info")
+	require.NoError(t, err)
+
+	modelName := model.NewCIStr("c1")
+	modelState := model.StatePublic
+	modelFieldType := *types.NewFieldType(mysql.TypeTiny)
+	c1 := &model.ColumnInfo{ID: 1, Name: modelName, State: modelState, Offset: 0, FieldType: modelFieldType}
+	cols := []*model.ColumnInfo{c1}
+	tblInfo := &model.TableInfo{ID: 1, Columns: cols, PKIsHandle: false, State: model.StatePublic}
+	var tbl table.Table
+	tbl, err = tables.TableFromMeta(NewPanickingAllocators(0), tblInfo)
+	require.NoError(t, err)
+
+	var baseKVEncoder *BaseKVEncoder
+	baseKVEncoder, err = NewBaseKVEncoder(&encode.EncodingConfig{
+		Table: tbl,
+		SessionOptions: encode.SessionOptions{
+			SQLMode:   mysql.ModeStrictAllTables,
+			Timestamp: 1234567890,
+		},
+		Logger: log.L(),
+	})
+	var newString strings.Builder
+	for i := 0; i < 100000; i++ {
+		newString.WriteString("test_test_test_test_")
+	}
+	newDatum := types.NewStringDatum(newString.String())
+	rows := []types.Datum{}
+	for i := 0; i <= 10; i++ {
+		rows = append(rows, newDatum)
+	}
+	err = baseKVEncoder.LogKVConvertFailed(rows, 6, c1, err)
+	require.NoError(t, err)
+
+	var content []byte
+	content, err = os.ReadFile(tempPath)
+	require.NoError(t, err)
+	require.LessOrEqual(t, 500, len(string(content)))
+	require.NotContains(t, content, "exceeds maximum file size")
+}