store/tikv: fix performance issue under mixed transaction mode

config/config.go

@@ -35,7 +35,9 @@ import (
 
 // Config number limitations
 const (
-	MaxLogFileSize = 4096 // MB
+	MaxLogFileSize    = 4096 // MB
+	MinPessimisticTTL = time.Second * 15
+	MaxPessimisticTTL = time.Second * 60
 )
 
 // Valid config maps
@@ -568,10 +570,9 @@ func (c *Config) Valid() error {
 		if err != nil {
 			return err
 		}
-		minDur := time.Second * 15
-		maxDur := time.Second * 60
-		if dur < minDur || dur > maxDur {
-			return fmt.Errorf("pessimistic transaction ttl %s out of range [%s, %s]", dur, minDur, maxDur)
+		if dur < MinPessimisticTTL || dur > MaxPessimisticTTL {
+			return fmt.Errorf("pessimistic transaction ttl %s out of range [%s, %s]",
+				dur, MinPessimisticTTL, MaxPessimisticTTL)
 		}
 	}
 	return nil

session/pessimistic_test.go

@@ -27,6 +27,7 @@ import (
 	"github.com/pingcap/tidb/session"
 	"github.com/pingcap/tidb/store/mockstore"
 	"github.com/pingcap/tidb/store/mockstore/mocktikv"
+	"github.com/pingcap/tidb/store/tikv"
 	"github.com/pingcap/tidb/tablecodec"
 	"github.com/pingcap/tidb/util/codec"
 	"github.com/pingcap/tidb/util/testkit"
@@ -52,6 +53,7 @@ func (s *testPessimisticSuite) SetUpSuite(c *C) {
 		mockstore.WithCluster(s.cluster),
 		mockstore.WithMVCCStore(s.mvccStore),
 	)
+	tikv.PessimisticLockTTL = uint64(config.MinPessimisticTTL / time.Millisecond)
 	c.Assert(err, IsNil)
 	s.store = store
 	session.SetSchemaLease(0)

store/tikv/2pc.go

@@ -538,6 +538,19 @@ func (c *twoPhaseCommitter) prewriteSingleBatch(bo *Backoffer, batch batchKeys)
 			if err1 != nil {
 				return errors.Trace(err1)
 			}
+			if !c.isPessimistic && c.lockTTL < lock.TTL && lock.TTL >= uint64(config.MinPessimisticTTL/time.Millisecond) {
+				// An optimistic prewrite meets a pessimistic or large transaction lock.
+				// If we wait for the lock, other written optimistic locks would block reads for long time.
+				// And it is very unlikely this transaction would succeed after wait for the long TTL lock.
+				// Return write conflict error to cleanup locks.
+				return newWriteConflictError(&pb.WriteConflict{
+					StartTs:          c.startTS,
+					ConflictTs:       lock.TxnID,
+					ConflictCommitTs: 0,
+					Key:              lock.Key,
+					Primary:          lock.Primary,
+				})
+			}
 			logutil.Logger(context.Background()).Debug("prewrite encounters lock",
 				zap.Uint64("conn", c.connID),
 				zap.Stringer("lock", lock))

store/tikv/2pc_test.go

@@ -23,6 +23,7 @@ import (
 	. "github.com/pingcap/check"
 	"github.com/pingcap/errors"
 	"github.com/pingcap/kvproto/pkg/kvrpcpb"
+	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/kv"
 	"github.com/pingcap/tidb/store/mockstore/mocktikv"
 	"github.com/pingcap/tidb/store/tikv/tikvrpc"
@@ -38,6 +39,7 @@ var _ = Suite(&testCommitterSuite{})
 
 func (s *testCommitterSuite) SetUpTest(c *C) {
 	s.cluster = mocktikv.NewCluster()
+	PessimisticLockTTL = uint64(config.MinPessimisticTTL / time.Millisecond)
 	mocktikv.BootstrapWithMultiRegions(s.cluster, []byte("a"), []byte("b"), []byte("c"))
 	mvccStore, err := mocktikv.NewMVCCLevelDB("")
 	c.Assert(err, IsNil)
@@ -468,3 +470,18 @@ func (s *testCommitterSuite) TestPessimisticLockedKeysDedup(c *C) {
 	c.Assert(err, IsNil)
 	c.Assert(txn.lockKeys, HasLen, 2)
 }
+
+func (s *testCommitterSuite) TestPessimistOptimisticConflict(c *C) {
+	txnPes := s.begin(c)
+	txnPes.SetOption(kv.Pessimistic, true)
+	err := txnPes.LockKeys(context.Background(), txnPes.startTS, kv.Key("pes"))
+	c.Assert(err, IsNil)
+	c.Assert(txnPes.IsPessimistic(), IsTrue)
+	c.Assert(txnPes.lockKeys, HasLen, 1)
+	txnOpt := s.begin(c)
+	err = txnOpt.Set(kv.Key("pes"), []byte("v"))
+	c.Assert(err, IsNil)
+	err = txnOpt.Commit(context.Background())
+	c.Assert(kv.ErrWriteConflict.Equal(err), IsTrue)
+	c.Assert(txnPes.Commit(context.Background()), IsNil)
+}

store/tikv/lock_resolver.go

@@ -138,17 +138,12 @@ func (l *Lock) String() string {
 
 // NewLock creates a new *Lock.
 func NewLock(l *kvrpcpb.LockInfo) *Lock {
-	ttl := l.GetLockTtl()
-	if ttl == 0 {
-		ttl = defaultLockTTL
-	}
-	txnSize := l.GetTxnSize()
 	return &Lock{
 		Key:     l.GetKey(),
 		Primary: l.GetPrimaryLock(),
 		TxnID:   l.GetLockVersion(),
-		TTL:     ttl,
-		TxnSize: txnSize,
+		TTL:     l.GetLockTtl(),
+		TxnSize: l.GetTxnSize(),
 	}
 }
 

store/tikv/lock_test.go

@@ -277,6 +277,11 @@ func (s *testLockSuite) TestLockTTL(c *C) {
 	s.ttlEquals(c, l.TTL, defaultLockTTL+uint64(time.Since(start)/time.Millisecond))
 }
 
+func (s *testLockSuite) TestNewLockZeroTTL(c *C) {
+	l := NewLock(&kvrpcpb.LockInfo{})
+	c.Assert(l.TTL, Equals, uint64(0))
+}
+
 func init() {
 	// Speed up tests.
 	defaultLockTTL = 3