diff --git a/ddl/backfilling_scheduler.go b/ddl/backfilling_scheduler.go
index 377f926c8c..a83db4cf9c 100644
--- a/ddl/backfilling_scheduler.go
+++ b/ddl/backfilling_scheduler.go
@@ -16,6 +16,7 @@ package ddl
 
 import (
 	"context"
+	"fmt"
 	"sync"
 	"time"
 
@@ -32,6 +33,7 @@ import (
 	"github.com/pingcap/tidb/table"
 	"github.com/pingcap/tidb/util"
 	"github.com/pingcap/tidb/util/dbterror"
+	"github.com/pingcap/tidb/util/intest"
 	"github.com/pingcap/tidb/util/logutil"
 	"github.com/pingcap/tidb/util/mathutil"
 	decoder "github.com/pingcap/tidb/util/rowDecoder"
@@ -343,6 +345,9 @@ func (b *ingestBackfillScheduler) close(force bool) {
 		}
 	}
 	close(b.resultCh)
+	if intest.InTest && len(b.copReqSenderPool.srcChkPool) != copReadChunkPoolSize() {
+		panic(fmt.Sprintf("unexpected chunk size %d", len(b.copReqSenderPool.srcChkPool)))
+	}
 	if !force {
 		jobID := b.reorgInfo.ID
 		indexID := b.reorgInfo.currElement.ID
@@ -450,13 +455,13 @@ func (w *addIndexIngestWorker) HandleTask(rs idxRecResult) {
 	defer util.Recover(metrics.LabelDDL, "ingestWorker.HandleTask", func() {
 		w.resultCh <- &backfillResult{taskID: rs.id, err: dbterror.ErrReorgPanic}
 	}, false)
-
+	defer w.copReqSenderPool.recycleChunk(rs.chunk)
 	result := &backfillResult{
 		taskID: rs.id,
 		err:    rs.err,
 	}
 	if result.err != nil {
-		logutil.BgLogger().Error("[ddl-ingest] finish a cop-request task with error",
+		logutil.BgLogger().Error("[ddl-ingest] encounter error when handle index chunk",
 			zap.Int("id", rs.id), zap.Error(rs.err))
 		w.resultCh <- result
 		return
diff --git a/ddl/index.go b/ddl/index.go
index df4914ebb9..d0153c848b 100644
--- a/ddl/index.go
+++ b/ddl/index.go
@@ -1611,10 +1611,8 @@ func (w *addIndexIngestWorker) WriteLocal(rs *idxRecResult) (count int, nextKey
 	vars := w.sessCtx.GetSessionVars()
 	cnt, lastHandle, err := writeChunkToLocal(w.writer, w.index, copCtx, vars, rs.chunk)
 	if err != nil || cnt == 0 {
-		w.copReqSenderPool.recycleChunk(rs.chunk)
 		return 0, nil, err
 	}
-	w.copReqSenderPool.recycleChunk(rs.chunk)
 	w.metricCounter.Add(float64(cnt))
 	logSlowOperations(time.Since(oprStartTime), "writeChunkToLocal", 3000)
 	nextKey = tablecodec.EncodeRecordKey(w.tbl.RecordPrefix(), lastHandle)
diff --git a/ddl/index_cop.go b/ddl/index_cop.go
index 9640304e6b..b02f23bfa2 100644
--- a/ddl/index_cop.go
+++ b/ddl/index_cop.go
@@ -144,7 +144,11 @@ func (c *copReqSender) run() {
 			if p.checkpointMgr != nil {
 				p.checkpointMgr.UpdateTotal(task.id, srcChk.NumRows(), done)
 			}
-			p.chunkSender.AddTask(idxRecResult{id: task.id, chunk: srcChk, done: done})
+			idxRs := idxRecResult{id: task.id, chunk: srcChk, done: done}
+			failpoint.Inject("MockCopSenderError", func() {
+				idxRs.err = errors.New("mock cop error")
+			})
+			p.chunkSender.AddTask(idxRs)
 		}
 		terror.Call(rs.Close)
 	}
diff --git a/ddl/ingest/BUILD.bazel b/ddl/ingest/BUILD.bazel
index 8821c971e0..318a20c2cc 100644
--- a/ddl/ingest/BUILD.bazel
+++ b/ddl/ingest/BUILD.bazel
@@ -59,7 +59,7 @@ go_test(
     ],
     flaky = True,
     race = "on",
-    shard_count = 6,
+    shard_count = 7,
     deps = [
         ":ingest",
         "//config",
@@ -68,6 +68,7 @@ go_test(
         "//sessionctx",
         "//testkit",
         "@com_github_ngaut_pools//:pools",
+        "@com_github_pingcap_failpoint//:failpoint",
         "@com_github_stretchr_testify//require",
     ],
 )
diff --git a/ddl/ingest/integration_test.go b/ddl/ingest/integration_test.go
index 3e51d52593..d30eaabc39 100644
--- a/ddl/ingest/integration_test.go
+++ b/ddl/ingest/integration_test.go
@@ -19,6 +19,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/pingcap/failpoint"
 	"github.com/pingcap/tidb/ddl/ingest"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/sessionctx"
@@ -47,10 +48,7 @@ func injectMockBackendMgr(t *testing.T, store kv.Storage) (restore func()) {
 func TestAddIndexIngestGeneratedColumns(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)
-	tk.MustExec("drop database if exists addindexlit;")
-	tk.MustExec("create database addindexlit;")
-	tk.MustExec("use addindexlit;")
-	tk.MustExec(`set global tidb_ddl_enable_fast_reorg=on;`)
+	tk.MustExec("use test;")
 	defer injectMockBackendMgr(t, store)()
 
 	assertLastNDDLUseIngest := func(n int) {
@@ -93,3 +91,26 @@ func TestAddIndexIngestGeneratedColumns(t *testing.T) {
 	tk.MustQuery("select * from t;").Check(testkit.Rows("1 1 1 2 1", "2 2 2 4 2", "3 3 3 6 3"))
 	assertLastNDDLUseIngest(4)
 }
+
+func TestIngestCopSenderErr(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test;")
+	defer injectMockBackendMgr(t, store)()
+
+	tk.MustExec("set @@global.tidb_ddl_reorg_worker_cnt = 1;")
+	tk.MustExec("create table t (a int primary key, b int);")
+	for i := 0; i < 4; i++ {
+		tk.MustExec(fmt.Sprintf("insert into t values (%d, %d);", i*10000, i*10000))
+	}
+	tk.MustQuery("split table t between (0) and (50000) regions 5;").Check(testkit.Rows("4 1"))
+
+	require.NoError(t, failpoint.Enable("github.com/pingcap/tidb/ddl/MockCopSenderError", "return"))
+	tk.MustExec("alter table t add index idx(a);")
+	require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/ddl/MockCopSenderError"))
+	tk.MustExec("admin check table t;")
+	rows := tk.MustQuery("admin show ddl jobs 1;").Rows()
+	//nolint: forcetypeassert
+	jobTp := rows[0][3].(string)
+	require.True(t, strings.Contains(jobTp, "txn-merge"), jobTp)
+}