fix issue read req timeout bug cause by pr#1223 (#1232)

* fix issue read req timeout bug cause by pr#1223

Signed-off-by: crazycs520 <crazycs520@gmail.com>

* add test

Signed-off-by: crazycs520 <crazycs520@gmail.com>

* fix test

Signed-off-by: crazycs520 <crazycs520@gmail.com>

* implement Cause

Signed-off-by: crazycs520 <crazycs520@gmail.com>

* fix race test

Signed-off-by: crazycs520 <crazycs520@gmail.com>

---------

Signed-off-by: crazycs520 <crazycs520@gmail.com>
Co-authored-by: you06 <you1474600@gmail.com>

internal/client/client.go

@@ -138,6 +138,10 @@ func (e *ErrConn) Error() string {
 	return fmt.Sprintf("[%s](%d) %s", e.Addr, e.Ver, e.Err.Error())
 }
 
+func (e *ErrConn) Cause() error {
+	return e.Err
+}
+
 func (e *ErrConn) Unwrap() error {
 	return e.Err
 }

internal/locate/replica_selector_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/tikv/client-go/v2/config/retry"
 	"github.com/tikv/client-go/v2/internal/apicodec"
 	"github.com/tikv/client-go/v2/internal/client"
+	"github.com/tikv/client-go/v2/internal/client/mockserver"
 	"github.com/tikv/client-go/v2/internal/logutil"
 	"github.com/tikv/client-go/v2/internal/mockstore/mocktikv"
 	"github.com/tikv/client-go/v2/kv"
@@ -3215,6 +3216,71 @@ func (s *testReplicaSelectorSuite) getRegion() *Region {
 	return nil
 }
 
+func TestTiKVClientReadTimeout(t *testing.T) {
+	if israce.RaceEnabled {
+		t.Skip("the test run with race will failed, so skip it")
+	}
+	config.UpdateGlobal(func(conf *config.Config) {
+		// enable batch client.
+		conf.TiKVClient.MaxBatchSize = 128
+	})()
+	s := new(testReplicaSelectorSuite)
+	s.SetupTest(t)
+	defer s.TearDownTest()
+
+	server, port := mockserver.StartMockTikvService()
+	s.True(port > 0)
+	server.SetMetaChecker(func(ctx context.Context) error {
+		time.Sleep(time.Millisecond * 10)
+		return nil
+	})
+	rpcClient := client.NewRPCClient()
+	defer func() {
+		rpcClient.Close()
+		server.Stop()
+	}()
+
+	accessPath := []string{}
+	fnClient := &fnClient{fn: func(ctx context.Context, addr string, req *tikvrpc.Request, timeout time.Duration) (response *tikvrpc.Response, err error) {
+		accessPath = append(accessPath, addr)
+		accessPath = append(accessPath, fmt.Sprintf("{addr: %v, replica-read: %v, stale-read: %v, timeout: %v}", addr, req.ReplicaRead, req.StaleRead, req.MaxExecutionDurationMs))
+		return rpcClient.SendRequest(ctx, server.Addr(), req, timeout)
+	}}
+	rc := s.getRegion()
+	s.NotNil(rc)
+	req := tikvrpc.NewRequest(tikvrpc.CmdGet, &kvrpcpb.GetRequest{Key: []byte("key"), Version: 1})
+	req.ReplicaReadType = kv.ReplicaReadLeader
+	req.MaxExecutionDurationMs = 1
+	bo := retry.NewBackofferWithVars(context.Background(), 2000, nil)
+	sender := NewRegionRequestSender(s.cache, fnClient)
+	resp, _, err := sender.SendReq(bo, req, rc.VerID(), time.Millisecond)
+	s.Nil(err)
+	s.NotNil(resp)
+	regionErr, _ := resp.GetRegionError()
+	s.True(IsFakeRegionError(regionErr))
+	s.Equal(0, bo.GetTotalBackoffTimes())
+	s.Equal([]string{
+		"store1", "{addr: store1, replica-read: false, stale-read: false, timeout: 1}",
+		"store2", "{addr: store2, replica-read: true, stale-read: false, timeout: 1}",
+		"store3", "{addr: store3, replica-read: true, stale-read: false, timeout: 1}",
+	}, accessPath)
+	// clear max execution duration for retry.
+	req.MaxExecutionDurationMs = 0
+	sender = NewRegionRequestSender(s.cache, fnClient)
+	resp, _, err = sender.SendReq(bo, req, rc.VerID(), time.Second) // use a longer timeout.
+	s.Nil(err)
+	s.NotNil(resp)
+	regionErr, _ = resp.GetRegionError()
+	s.Nil(regionErr)
+	s.Equal(0, bo.GetTotalBackoffTimes())
+	s.Equal([]string{
+		"store1", "{addr: store1, replica-read: false, stale-read: false, timeout: 1}",
+		"store2", "{addr: store2, replica-read: true, stale-read: false, timeout: 1}",
+		"store3", "{addr: store3, replica-read: true, stale-read: false, timeout: 1}",
+		"store1", "{addr: store1, replica-read: true, stale-read: false, timeout: 1000}",
+	}, accessPath)
+}
+
 func BenchmarkReplicaSelector(b *testing.B) {
 	mvccStore := mocktikv.MustNewMVCCStore()
 	cluster := mocktikv.NewCluster(mvccStore)