ddl: let admin cancel ddl jobs run in a new transaction

ddl/db_test.go

@@ -61,6 +61,7 @@ import (
 	"github.com/pingcap/tidb/util/domainutil"
 	"github.com/pingcap/tidb/util/israce"
 	"github.com/pingcap/tidb/util/mock"
+	"github.com/pingcap/tidb/util/sqlexec"
 	"github.com/pingcap/tidb/util/testkit"
 	"github.com/pingcap/tidb/util/testutil"
 	"github.com/tikv/client-go/v2/testutils"
@@ -7290,6 +7291,51 @@ func (s *testSerialDBSuite) TestJsonUnmarshalErrWhenPanicInCancellingPath(c *C)
 	c.Assert(err.Error(), Equals, "[kv:1062]Duplicate entry '0' for key 'cc'")
 }
 
+// Close issue #24172.
+// See https://github.com/pingcap/tidb/issues/24172
+func (s *testSerialDBSuite) TestCancelJobWriteConflict(c *C) {
+	tk := testkit.NewTestKitWithInit(c, s.store)
+	tk1 := testkit.NewTestKitWithInit(c, s.store)
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t(id int)")
+
+	var cancelErr error
+	var rs []sqlexec.RecordSet
+	hook := &ddl.TestDDLCallback{}
+	d := s.dom.DDL()
+	originalHook := d.GetHook()
+	d.(ddl.DDLForTest).SetHook(hook)
+	defer d.(ddl.DDLForTest).SetHook(originalHook)
+
+	// Cancelling will be retried but it still fails, and adding index succeeds.
+	hook.OnJobRunBeforeExported = func(job *model.Job) {
+		if job.Type == model.ActionAddIndex && job.State == model.JobStateRunning && job.SchemaState == model.StateWriteReorganization {
+			stmt := fmt.Sprintf("admin cancel ddl jobs %d", job.ID)
+			c.Assert(failpoint.Enable("github.com/pingcap/tidb/kv/mockCommitErrorInNewTxn", `return("everytime")`), IsNil)
+			defer func() { c.Assert(failpoint.Disable("github.com/pingcap/tidb/kv/mockCommitErrorInNewTxn"), IsNil) }()
+			rs, cancelErr = tk1.Se.Execute(context.Background(), stmt)
+		}
+	}
+	tk.MustExec("alter table t add index (id)")
+	c.Assert(cancelErr.Error(), Equals, "mock commit error")
+
+	// Cancelling will be retried only once and it succeeds at the end.
+	var jobID int64
+	hook.OnJobRunBeforeExported = func(job *model.Job) {
+		if job.Type == model.ActionAddIndex && job.State == model.JobStateRunning && job.SchemaState == model.StateWriteReorganization {
+			jobID = job.ID
+			stmt := fmt.Sprintf("admin cancel ddl jobs %d", job.ID)
+			c.Assert(failpoint.Enable("github.com/pingcap/tidb/kv/mockCommitErrorInNewTxn", `return("once")`), IsNil)
+			defer func() { c.Assert(failpoint.Disable("github.com/pingcap/tidb/kv/mockCommitErrorInNewTxn"), IsNil) }()
+			rs, cancelErr = tk1.Se.Execute(context.Background(), stmt)
+		}
+	}
+	tk.MustGetErrCode("alter table t add index (id)", errno.ErrCancelledDDLJob)
+	c.Assert(cancelErr, IsNil)
+	result := tk1.ResultSetToResultWithCtx(context.Background(), rs[0], Commentf("cancel ddl job fails"))
+	result.Check(testkit.Rows(fmt.Sprintf("%d successful", jobID)))
+}
+
 // For Close issue #24288
 // see https://github.com/pingcap/tidb/issues/24288
 func (s *testDBSuite8) TestDdlMaxLimitOfIdentifier(c *C) {

executor/builder.go

@@ -283,15 +283,13 @@ func (b *executorBuilder) buildCancelDDLJobs(v *plannercore.CancelDDLJobs) Execu
 		baseExecutor: newBaseExecutor(b.ctx, v.Schema(), v.ID()),
 		jobIDs:       v.JobIDs,
 	}
-	txn, err := e.ctx.Txn(true)
-	if err != nil {
-		b.err = err
-		return nil
-	}
-
-	e.errs, b.err = admin.CancelJobs(txn, e.jobIDs)
-	if b.err != nil {
-		return nil
+	// Run within a new transaction. If it runs within the session transaction, commit failure won't be reported to the user.
+	errInTxn := kv.RunInNewTxn(context.Background(), e.ctx.GetStore(), true, func(ctx context.Context, txn kv.Transaction) (err error) {
+		e.errs, err = admin.CancelJobs(txn, e.jobIDs)
+		return
+	})
+	if errInTxn != nil {
+		b.err = errInTxn
 	}
 	return e
 }

kv/txn.go

@@ -16,10 +16,12 @@ package kv
 
 import (
 	"context"
+	"errors"
 	"math"
 	"math/rand"
 	"time"
 
+	"github.com/pingcap/failpoint"
 	"github.com/pingcap/tidb/parser/terror"
 	"github.com/pingcap/tidb/util/logutil"
 	"go.uber.org/zap"
@@ -58,9 +60,24 @@ func RunInNewTxn(ctx context.Context, store Storage, retryable bool, f func(ctx
 			return err
 		}
 
-		err = txn.Commit(ctx)
+		failpoint.Inject("mockCommitErrorInNewTxn", func(val failpoint.Value) {
+			if v := val.(string); len(v) > 0 {
+				switch v {
+				case "once":
+					if i == 0 {
+						err = ErrTxnRetryable
+					}
+				case "everytime":
+					failpoint.Return(errors.New("mock commit error"))
+				}
+			}
+		})
+
 		if err == nil {
-			break
+			err = txn.Commit(ctx)
+			if err == nil {
+				break
+			}
 		}
 		if retryable && IsTxnRetryableError(err) {
 			logutil.BgLogger().Warn("RunInNewTxn",