store/tikv: Fix the issue that context canceled error during commit RPC is not treated as undetermined error (#20857)

store/tikv/2pc_test.go

@@ -239,6 +239,27 @@ func (s *testCommitterSuite) TestContextCancelRetryable(c *C) {
 	c.Assert(kv.ErrWriteConflictInTiDB.Equal(err), IsTrue, Commentf("err: %s", err))
 }
 
+func (s *testCommitterSuite) TestContextCancelCausingUndetermined(c *C) {
+	// For a normal transaction, if RPC returns context.Canceled error while sending commit
+	// requests, the transaction should go to the undetermined state.
+	txn := s.begin(c)
+	err := txn.Set([]byte("a"), []byte("va"))
+	c.Assert(err, IsNil)
+	committer, err := newTwoPhaseCommitterWithInit(txn, 0)
+	c.Assert(err, IsNil)
+	committer.prewriteMutations(NewBackofferWithVars(context.Background(), PrewriteMaxBackoff, nil), committer.mutations)
+	c.Assert(err, IsNil)
+
+	c.Assert(failpoint.Enable("github.com/pingcap/tidb/store/tikv/rpcContextCancelErr", `return(true)`), IsNil)
+	defer func() {
+		c.Assert(failpoint.Disable("github.com/pingcap/tidb/store/tikv/rpcContextCancelErr"), IsNil)
+	}()
+
+	err = committer.commitMutations(NewBackofferWithVars(context.Background(), PrewriteMaxBackoff, nil), committer.mutations)
+	c.Assert(committer.mu.undeterminedErr, NotNil)
+	c.Assert(errors.Cause(err), Equals, context.Canceled)
+}
+
 func (s *testCommitterSuite) mustGetRegionID(c *C, key []byte) uint64 {
 	loc, err := s.store.regionCache.LocateKey(NewBackofferWithVars(context.Background(), getMaxBackoff, nil), key)
 	c.Assert(err, IsNil)

store/tikv/region_request.go

@@ -407,15 +407,31 @@ func (s *RegionRequestSender) sendReqToRegion(bo *Backoffer, rpcCtx *RPCContext,
 			}
 		})
 	}
+
+	failpoint.Inject("rpcContextCancelErr", func(val failpoint.Value) {
+		if val.(bool) {
+			ctx1, cancel := context.WithCancel(context.Background())
+			cancel()
+			select {
+			case <-ctx1.Done():
+			}
+
+			ctx = ctx1
+			err = ctx.Err()
+			resp = nil
+		}
+	})
+
 	if err != nil {
+		s.rpcError = err
+
 		// Because in rpc logic, context.Cancel() will be transferred to rpcContext.Cancel error. For rpcContext cancel,
 		// we need to retry the request. But for context cancel active, for example, limitExec gets the required rows,
 		// we shouldn't retry the request, it will go to backoff and hang in retry logic.
 		if ctx.Err() != nil && errors.Cause(ctx.Err()) == context.Canceled {
 			return nil, false, errors.Trace(ctx.Err())
 		}
 
-		s.rpcError = err
 		if e := s.onSendFail(bo, rpcCtx, err); e != nil {
 			return nil, false, errors.Trace(e)
 		}