Golang BatchRequest.Txn方法代碼示例

// TestTxnCoordSenderErrorWithIntent validates that if a transactional request
// returns an error but also indicates a Writing transaction, the coordinator
// tracks it just like a successful request.
func TestTxnCoordSenderErrorWithIntent(t *testing.T) {
	defer leaktest.AfterTest(t)
	stopper := stop.NewStopper()
	manual := hlc.NewManualClock(0)
	clock := hlc.NewClock(manual.UnixNano)
	clock.SetMaxOffset(20)

	ts := NewTxnCoordSender(senderFn(func(_ context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
		txn := ba.Txn.Clone()
		txn.Writing = true
		pErr := roachpb.NewError(roachpb.NewTransactionRetryError())
		pErr.SetTxn(txn)
		return nil, pErr
	}), clock, false, nil, stopper)
	defer stopper.Stop()

	var ba roachpb.BatchRequest
	key := roachpb.Key("test")
	ba.Add(&roachpb.BeginTransactionRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.PutRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.EndTransactionRequest{})
	ba.Txn = &roachpb.Transaction{Name: "test"}
	if _, pErr := ts.Send(context.Background(), ba); !testutils.IsPError(pErr, "retry txn") {
		t.Fatalf("unexpected error: %v", pErr)
	}

	defer teardownHeartbeats(ts)
	ts.Lock()
	defer ts.Unlock()
	if len(ts.txns) != 1 {
		t.Fatalf("expected transaction to be tracked")
	}
}

// TestTxnCoordSenderSingleRoundtripTxn checks that a batch which completely
// holds the writing portion of a Txn (including EndTransaction) does not
// launch a heartbeat goroutine at all.
func TestTxnCoordSenderSingleRoundtripTxn(t *testing.T) {
	defer leaktest.AfterTest(t)
	stopper := stop.NewStopper()
	manual := hlc.NewManualClock(0)
	clock := hlc.NewClock(manual.UnixNano)
	clock.SetMaxOffset(20)

	ts := NewTxnCoordSender(senderFn(func(_ context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
		br := ba.CreateReply()
		br.Txn = ba.Txn.Clone()
		br.Txn.Writing = true
		return br, nil
	}), clock, false, nil, stopper)

	// Stop the stopper manually, prior to trying the transaction. This has the
	// effect of returning a NodeUnavailableError for any attempts at launching
	// a heartbeat goroutine.
	stopper.Stop()

	var ba roachpb.BatchRequest
	key := roachpb.Key("test")
	ba.Add(&roachpb.BeginTransactionRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.PutRequest{Span: roachpb.Span{Key: key}})
	ba.Add(&roachpb.EndTransactionRequest{})
	ba.Txn = &roachpb.Transaction{Name: "test"}
	_, pErr := ts.Send(context.Background(), ba)
	if pErr != nil {
		t.Fatal(pErr)
	}
}

func (ts *txnSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	// Send call through wrapped sender.
	ba.Txn = &ts.Proto
	ba.SetNewRequest()
	br, pErr := ts.wrapped.Send(ctx, ba)
	if br != nil && br.Error != nil {
		panic(roachpb.ErrorUnexpectedlySet(ts.wrapped, br))
	}

	// Only successful requests can carry an updated Txn in their response
	// header. Any error (e.g. a restart) can have a Txn attached to them as
	// well; those update our local state in the same way for the next attempt.
	// The exception is if our transaction was aborted and needs to restart
	// from scratch, in which case we do just that.
	if pErr == nil {
		ts.Proto.Update(br.Txn)
		return br, nil
	} else if _, ok := pErr.GoError().(*roachpb.TransactionAbortedError); ok {
		// On Abort, reset the transaction so we start anew on restart.
		ts.Proto = roachpb.Transaction{
			Name:      ts.Proto.Name,
			Isolation: ts.Proto.Isolation,
		}
		// Acts as a minimum priority on restart.
		if pErr.GetTxn() != nil {
			ts.Proto.Priority = pErr.GetTxn().Priority
		}
	} else if pErr.TransactionRestart != roachpb.TransactionRestart_ABORT {
		ts.Proto.Update(pErr.GetTxn())
	}
	return nil, pErr
}

func (ts *txnSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	// Send call through wrapped sender.
	ba.Txn = &ts.Proto
	br, pErr := ts.wrapped.Send(ctx, ba)
	if br != nil && br.Error != nil {
		panic(roachpb.ErrorUnexpectedlySet(ts.wrapped, br))
	}

	// TODO(tschottdorf): see about using only the top-level *roachpb.Error
	// information for this restart logic (includes adding the Txn).
	err := pErr.GoError()
	// Only successful requests can carry an updated Txn in their response
	// header. Any error (e.g. a restart) can have a Txn attached to them as
	// well; those update our local state in the same way for the next attempt.
	// The exception is if our transaction was aborted and needs to restart
	// from scratch, in which case we do just that.
	if err == nil {
		ts.Proto.Update(br.Txn)
		return br, nil
	} else if abrtErr, ok := err.(*roachpb.TransactionAbortedError); ok {
		// On Abort, reset the transaction so we start anew on restart.
		ts.Proto = roachpb.Transaction{
			Name:      ts.Proto.Name,
			Isolation: ts.Proto.Isolation,
		}
		if abrtTxn := abrtErr.Transaction(); abrtTxn != nil {
			// Acts as a minimum priority on restart.
			ts.Proto.Priority = abrtTxn.Priority
		}
	} else if txnErr, ok := err.(roachpb.TransactionRestartError); ok {
		ts.Proto.Update(txnErr.Transaction())
	}
	return nil, pErr
}

// Send implements the client.Sender interface. The store is looked up from the
// store map if specified by the request; otherwise, the command is being
// executed locally, and the replica is determined via lookup through each
// store's LookupRange method. The latter path is taken only by unit tests.
func (ls *Stores) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	var store *Store
	var err error

	// If we aren't given a Replica, then a little bending over
	// backwards here. This case applies exclusively to unittests.
	if ba.RangeID == 0 || ba.Replica.StoreID == 0 {
		var repl *roachpb.ReplicaDescriptor
		var rangeID roachpb.RangeID
		rs := keys.Range(ba)
		rangeID, repl, err = ls.lookupReplica(rs.Key, rs.EndKey)
		if err == nil {
			ba.RangeID = rangeID
			ba.Replica = *repl
		}
	}

	ctx = log.Add(ctx,
		log.RangeID, ba.RangeID)

	if err == nil {
		store, err = ls.GetStore(ba.Replica.StoreID)
	}

	if err != nil {
		return nil, roachpb.NewError(err)
	}

	sp, cleanupSp := tracing.SpanFromContext(opStores, store.Tracer(), ctx)
	defer cleanupSp()
	if ba.Txn != nil {
		// For calls that read data within a txn, we keep track of timestamps
		// observed from the various participating nodes' HLC clocks. If we have
		// a timestamp on file for this Node which is smaller than MaxTimestamp,
		// we can lower MaxTimestamp accordingly. If MaxTimestamp drops below
		// OrigTimestamp, we effectively can't see uncertainty restarts any
		// more.
		// Note that it's not an issue if MaxTimestamp propagates back out to
		// the client via a returned Transaction update - when updating a Txn
		// from another, the larger MaxTimestamp wins.
		if maxTS, ok := ba.Txn.GetObservedTimestamp(ba.Replica.NodeID); ok && maxTS.Less(ba.Txn.MaxTimestamp) {
			// Copy-on-write to protect others we might be sharing the Txn with.
			shallowTxn := *ba.Txn
			// The uncertainty window is [OrigTimestamp, maxTS), so if that window
			// is empty, there won't be any uncertainty restarts.
			if !ba.Txn.OrigTimestamp.Less(maxTS) {
				sp.LogEvent("read has no clock uncertainty")
			}
			shallowTxn.MaxTimestamp.Backward(maxTS)
			ba.Txn = &shallowTxn
		}
	}
	br, pErr := store.Send(ctx, ba)
	if br != nil && br.Error != nil {
		panic(roachpb.ErrorUnexpectedlySet(store, br))
	}
	return br, pErr
}

func (tc *TxnCoordSender) heartbeat(id string, trace *tracer.Trace, ctx context.Context) bool {
	tc.Lock()
	proceed := true
	txnMeta := tc.txns[id]
	// Before we send a heartbeat, determine whether this transaction
	// should be considered abandoned. If so, exit heartbeat.
	if txnMeta.hasClientAbandonedCoord(tc.clock.PhysicalNow()) {
		// TODO(tschottdorf): should we be more proactive here?
		// The client might be continuing the transaction
		// through another coordinator, but in the most likely
		// case it's just gone and the open transaction record
		// could block concurrent operations.
		if log.V(1) {
			log.Infof("transaction %s abandoned; stopping heartbeat",
				txnMeta.txn)
		}
		proceed = false
	}
	// txnMeta.txn is possibly replaced concurrently,
	// so grab a copy before unlocking.
	txn := txnMeta.txn
	tc.Unlock()
	if !proceed {
		return false
	}

	hb := &roachpb.HeartbeatTxnRequest{}
	hb.Key = txn.Key
	ba := roachpb.BatchRequest{}
	ba.Timestamp = tc.clock.Now()
	ba.CmdID = ba.GetOrCreateCmdID(ba.Timestamp.WallTime)
	ba.Txn = txn.Clone()
	ba.Add(hb)

	epochEnds := trace.Epoch("heartbeat")
	_, err := tc.wrapped.Send(ctx, ba)
	epochEnds()
	// If the transaction is not in pending state, then we can stop
	// the heartbeat. It's either aborted or committed, and we resolve
	// write intents accordingly.
	if err != nil {
		log.Warningf("heartbeat to %s failed: %s", txn, err)
	}
	// TODO(bdarnell): once we have gotten a heartbeat response with
	// Status != PENDING, future heartbeats are useless. However, we
	// need to continue the heartbeatLoop until the client either
	// commits or abandons the transaction. We could save a little
	// pointless work by restructuring this loop to stop sending
	// heartbeats between the time that the transaction is aborted and
	// the client finds out. Furthermore, we could use this information
	// to send TransactionAbortedErrors to the client so it can restart
	// immediately instead of running until its EndTransaction.
	return true
}

// Send implements the client.Sender interface. The store is looked up from the
// store map if specified by the request; otherwise, the command is being
// executed locally, and the replica is determined via lookup through each
// store's LookupRange method. The latter path is taken only by unit tests.
func (ls *Stores) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	sp := tracing.SpanFromContext(ctx)
	var store *Store
	var pErr *roachpb.Error

	// If we aren't given a Replica, then a little bending over
	// backwards here. This case applies exclusively to unittests.
	if ba.RangeID == 0 || ba.Replica.StoreID == 0 {
		var repl *roachpb.ReplicaDescriptor
		var rangeID roachpb.RangeID
		rs := keys.Range(ba)
		rangeID, repl, pErr = ls.lookupReplica(rs.Key, rs.EndKey)
		if pErr == nil {
			ba.RangeID = rangeID
			ba.Replica = *repl
		}
	}

	ctx = log.Add(ctx,
		log.RangeID, ba.RangeID)

	if pErr == nil {
		store, pErr = ls.GetStore(ba.Replica.StoreID)
	}

	var br *roachpb.BatchResponse
	if pErr != nil {
		return nil, pErr
	}
	// For calls that read data within a txn, we can avoid uncertainty
	// related retries in certain situations. If the node is in
	// "CertainNodes", we need not worry about uncertain reads any
	// more. Setting MaxTimestamp=OrigTimestamp for the operation
	// accomplishes that. See roachpb.Transaction.CertainNodes for details.
	if ba.Txn != nil && ba.Txn.CertainNodes.Contains(ba.Replica.NodeID) {
		// MaxTimestamp = Timestamp corresponds to no clock uncertainty.
		sp.LogEvent("read has no clock uncertainty")
		// Copy-on-write to protect others we might be sharing the Txn with.
		shallowTxn := *ba.Txn
		// We set to OrigTimestamp because that works for both SNAPSHOT and
		// SERIALIZABLE: If we used Timestamp instead, we could run into
		// unnecessary retries at SNAPSHOT. For example, a SNAPSHOT txn at
		// OrigTimestamp = 1000.0, Timestamp = 2000.0, MaxTimestamp = 3000.0
		// will always read at 1000, so a MaxTimestamp of 2000 will still let
		// it restart with uncertainty when it finds a value in (1000, 2000).
		shallowTxn.MaxTimestamp = ba.Txn.OrigTimestamp
		ba.Txn = &shallowTxn
	}
	br, pErr = store.Send(ctx, ba)
	if br != nil && br.Error != nil {
		panic(roachpb.ErrorUnexpectedlySet(store, br))
	}
	return br, pErr
}

// TestTxnCoordSenderErrorWithIntent validates that if a transactional request
// returns an error but also indicates a Writing transaction, the coordinator
// tracks it just like a successful request.
func TestTxnCoordSenderErrorWithIntent(t *testing.T) {
	defer leaktest.AfterTest(t)()
	stopper := stop.NewStopper()
	defer stopper.Stop()
	manual := hlc.NewManualClock(0)
	clock := hlc.NewClock(manual.UnixNano)
	clock.SetMaxOffset(20)

	testCases := []struct {
		roachpb.Error
		errMsg string
	}{
		{*roachpb.NewError(roachpb.NewTransactionRetryError()), "retry txn"},
		{*roachpb.NewError(roachpb.NewTransactionPushError(roachpb.Transaction{
			TxnMeta: enginepb.TxnMeta{
				ID: uuid.NewV4(),
			}})), "failed to push"},
		{*roachpb.NewErrorf("testError"), "testError"},
	}
	for i, test := range testCases {
		func() {
			senderFunc := func(_ context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
				txn := ba.Txn.Clone()
				txn.Writing = true
				pErr := &roachpb.Error{}
				*pErr = test.Error
				pErr.SetTxn(&txn)
				return nil, pErr
			}
			ctx := tracing.WithTracer(context.Background(), tracing.NewTracer())
			ts := NewTxnCoordSender(ctx, senderFn(senderFunc), clock, false, stopper, MakeTxnMetrics())

			var ba roachpb.BatchRequest
			key := roachpb.Key("test")
			ba.Add(&roachpb.BeginTransactionRequest{Span: roachpb.Span{Key: key}})
			ba.Add(&roachpb.PutRequest{Span: roachpb.Span{Key: key}})
			ba.Add(&roachpb.EndTransactionRequest{})
			ba.Txn = &roachpb.Transaction{Name: "test"}
			_, pErr := ts.Send(context.Background(), ba)
			if !testutils.IsPError(pErr, test.errMsg) {
				t.Errorf("%d: error did not match %s: %v", i, test.errMsg, pErr)
			}

			defer teardownHeartbeats(ts)
			ts.Lock()
			defer ts.Unlock()
			if len(ts.txns) != 1 {
				t.Errorf("%d: expected transaction to be tracked", i)
			}
		}()
	}
}

func (ts *txnSender) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	// Send call through wrapped sender.
	ba.Txn = &ts.Proto
	if ts.UserPriority > 0 {
		ba.UserPriority = ts.UserPriority
	}

	ctx = opentracing.ContextWithSpan(ctx, ts.Trace)

	ba.SetNewRequest()
	br, pErr := ts.wrapped.Send(ctx, ba)
	if br != nil && br.Error != nil {
		panic(roachpb.ErrorUnexpectedlySet(ts.wrapped, br))
	}

	if br != nil {
		for _, encSp := range br.CollectedSpans {
			var newSp basictracer.RawSpan
			if err := tracing.DecodeRawSpan(encSp, &newSp); err != nil {
				return nil, roachpb.NewError(err)
			}
			ts.CollectedSpans = append(ts.CollectedSpans, newSp)
		}
	}
	// Only successful requests can carry an updated Txn in their response
	// header. Any error (e.g. a restart) can have a Txn attached to them as
	// well; those update our local state in the same way for the next attempt.
	// The exception is if our transaction was aborted and needs to restart
	// from scratch, in which case we do just that.
	if pErr == nil {
		ts.Proto.Update(br.Txn)
		return br, nil
	} else if _, ok := pErr.GetDetail().(*roachpb.TransactionAbortedError); ok {
		// On Abort, reset the transaction so we start anew on restart.
		ts.Proto = roachpb.Transaction{
			TxnMeta: roachpb.TxnMeta{
				Isolation: ts.Proto.Isolation,
			},
			Name: ts.Proto.Name,
		}
		// Acts as a minimum priority on restart.
		if pErr.GetTxn() != nil {
			ts.Proto.Priority = pErr.GetTxn().Priority
		}
	} else if pErr.TransactionRestart != roachpb.TransactionRestart_ABORT {
		ts.Proto.Update(pErr.GetTxn())
	}
	return nil, pErr
}

// Send implements the client.Sender interface. The store is looked up from the
// store map if specified by the request; otherwise, the command is being
// executed locally, and the replica is determined via lookup through each
// store's LookupRange method. The latter path is taken only by unit tests.
func (ls *Stores) Send(ctx context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	sp := tracing.SpanFromContext(ctx)
	var store *Store
	var pErr *roachpb.Error

	// If we aren't given a Replica, then a little bending over
	// backwards here. This case applies exclusively to unittests.
	if ba.RangeID == 0 || ba.Replica.StoreID == 0 {
		var repl *roachpb.ReplicaDescriptor
		var rangeID roachpb.RangeID
		rs := keys.Range(ba)
		rangeID, repl, pErr = ls.lookupReplica(rs.Key, rs.EndKey)
		if pErr == nil {
			ba.RangeID = rangeID
			ba.Replica = *repl
		}
	}

	ctx = log.Add(ctx,
		log.RangeID, ba.RangeID)

	if pErr == nil {
		store, pErr = ls.GetStore(ba.Replica.StoreID)
	}

	var br *roachpb.BatchResponse
	if pErr != nil {
		return nil, pErr
	}
	// For calls that read data within a txn, we can avoid uncertainty
	// related retries in certain situations. If the node is in
	// "CertainNodes", we need not worry about uncertain reads any
	// more. Setting MaxTimestamp=Timestamp for the operation
	// accomplishes that. See roachpb.Transaction.CertainNodes for details.
	if ba.Txn != nil && ba.Txn.CertainNodes.Contains(ba.Replica.NodeID) {
		// MaxTimestamp = Timestamp corresponds to no clock uncertainty.
		sp.LogEvent("read has no clock uncertainty")
		// Copy-on-write to protect others we might be sharing the Txn with.
		shallowTxn := *ba.Txn
		shallowTxn.MaxTimestamp = ba.Txn.Timestamp
		ba.Txn = &shallowTxn
	}
	br, pErr = store.Send(ctx, ba)
	if br != nil && br.Error != nil {
		panic(roachpb.ErrorUnexpectedlySet(store, br))
	}
	return br, pErr
}

// maybeBeginTxn begins a new transaction if a txn has been specified
// in the request but has a nil ID. The new transaction is initialized
// using the name and isolation in the otherwise uninitialized txn.
// The Priority, if non-zero is used as a minimum.
//
// No transactional writes are allowed unless preceded by a begin
// transaction request within the same batch. The exception is if the
// transaction is already in state txn.Writing=true.
func (tc *TxnCoordSender) maybeBeginTxn(ba *roachpb.BatchRequest) error {
	if ba.Txn == nil {
		return nil
	}
	if len(ba.Requests) == 0 {
		return util.Errorf("empty batch with txn")
	}
	if ba.Txn.ID == nil {
		// Create transaction without a key. The key is set when a begin
		// transaction request is received.

		// The initial timestamp may be communicated by a higher layer.
		// If so, use that. Otherwise make up a new one.
		timestamp := ba.Txn.OrigTimestamp
		if timestamp == roachpb.ZeroTimestamp {
			timestamp = tc.clock.Now()
		}
		newTxn := roachpb.NewTransaction(ba.Txn.Name, nil, ba.UserPriority,
			ba.Txn.Isolation, timestamp, tc.clock.MaxOffset().Nanoseconds())
		// Use existing priority as a minimum. This is used on transaction
		// aborts to ratchet priority when creating successor transaction.
		if newTxn.Priority < ba.Txn.Priority {
			newTxn.Priority = ba.Txn.Priority
		}
		ba.Txn = newTxn
	}

	// Check for a begin transaction to set txn key based on the key of
	// the first transactional write. Also enforce that no transactional
	// writes occur before a begin transaction.
	var haveBeginTxn bool
	for _, req := range ba.Requests {
		args := req.GetInner()
		if bt, ok := args.(*roachpb.BeginTransactionRequest); ok {
			if haveBeginTxn || ba.Txn.Writing {
				return util.Errorf("begin transaction requested twice in the same transaction: %s", ba.Txn)
			}
			haveBeginTxn = true
			if ba.Txn.Key == nil {
				ba.Txn.Key = bt.Key
			}
		}
		if roachpb.IsTransactionWrite(args) && !haveBeginTxn && !ba.Txn.Writing {
			return util.Errorf("transactional write before begin transaction")
		}
	}
	return nil
}

func (tc *TxnCoordSender) clientHasAbandoned(txnID uuid.UUID) {
	tc.Lock()
	txnMeta := tc.txns[txnID]
	var intentSpans []roachpb.Span

	// TODO(tschottdorf): should we be more proactive here?
	// The client might be continuing the transaction
	// through another coordinator, but in the most likely
	// case it's just gone and the open transaction record
	// could block concurrent operations.
	if log.V(1) {
		log.Infof("transaction %s abandoned; stopping heartbeat", txnMeta.txn)
	}
	// Grab the intents here to avoid potential race.
	intentSpans = collectIntentSpans(txnMeta.keys)
	txnMeta.keys.Clear()

	// txnMeta.txn is possibly replaced concurrently,
	// so grab a copy before unlocking.
	txn := txnMeta.txn.Clone()
	tc.Unlock()

	ba := roachpb.BatchRequest{}
	ba.Txn = &txn

	// Actively abort the transaction and its intents since we assume it's abandoned.
	et := &roachpb.EndTransactionRequest{
		Span: roachpb.Span{
			Key: txn.Key,
		},
		Commit:      false,
		IntentSpans: intentSpans,
	}
	ba.Add(et)
	tc.stopper.RunAsyncTask(func() {
		// Use the wrapped sender since the normal Sender
		// does not allow clients to specify intents.
		// TODO(tschottdorf): not using the existing context here since that
		// leads to use-after-finish of the contained trace. Should fork off
		// before the goroutine.
		if _, pErr := tc.wrapped.Send(context.Background(), ba); pErr != nil {
			if log.V(1) {
				log.Warningf("abort due to inactivity failed for %s: %s ", txn, pErr)
			}
		}
	})
}

// tryAsyncAbort (synchronously) grabs a copy of the txn proto and the intents
// (which it then clears from txnMeta), and asynchronously tries to abort the
// transaction.
func (tc *TxnCoordSender) tryAsyncAbort(txnID uuid.UUID) {
	tc.Lock()
	txnMeta := tc.txns[txnID]
	// Clone the intents and the txn to avoid data races.
	txnMeta.keys = append([]roachpb.Span(nil), txnMeta.keys...)
	roachpb.MergeSpans(&txnMeta.keys)
	intentSpans := txnMeta.keys
	txnMeta.keys = nil
	txn := txnMeta.txn.Clone()
	tc.Unlock()

	// Since we don't hold the lock continuously, it's possible that two aborts
	// raced here. That's fine (and probably better than the alternative, which
	// is missing new intents sometimes).
	if txn.Status != roachpb.PENDING {
		return
	}

	ba := roachpb.BatchRequest{}
	ba.Txn = &txn

	et := &roachpb.EndTransactionRequest{
		Span: roachpb.Span{
			Key: txn.Key,
		},
		Commit:      false,
		IntentSpans: intentSpans,
	}
	ba.Add(et)
	if err := tc.stopper.RunAsyncTask(func() {
		// Use the wrapped sender since the normal Sender does not allow
		// clients to specify intents.
		// TODO(tschottdorf): not using the existing context here since that
		// leads to use-after-finish of the contained trace. Should fork off
		// before the goroutine.
		if _, pErr := tc.wrapped.Send(context.Background(), ba); pErr != nil {
			if log.V(1) {
				log.Warningf("abort due to inactivity failed for %s: %s ", txn, pErr)
			}
		}
	}); err != nil {
		log.Warning(err)
	}
}

func (tc *TxnCoordSender) heartbeat(ctx context.Context, txnID uuid.UUID) bool {
	tc.Lock()
	txnMeta := tc.txns[txnID]
	txn := txnMeta.txn.Clone()
	tc.Unlock()

	// Before we send a heartbeat, determine whether this transaction should be
	// considered abandoned. If so, exit heartbeat. If ctx.Done() is not nil, then
	// it is a cancellable Context and we skip this check and use the ctx lifetime
	// instead of a timeout.
	if ctx.Done() == nil && txnMeta.hasClientAbandonedCoord(tc.clock.PhysicalNow()) {
		tc.clientHasAbandoned(txnID)
		return false
	}

	ba := roachpb.BatchRequest{}
	ba.Txn = &txn

	hb := &roachpb.HeartbeatTxnRequest{
		Now: tc.clock.Now(),
	}
	hb.Key = txn.Key
	ba.Add(hb)

	log.Trace(ctx, "heartbeat")
	_, err := tc.wrapped.Send(ctx, ba)
	// If the transaction is not in pending state, then we can stop
	// the heartbeat. It's either aborted or committed, and we resolve
	// write intents accordingly.
	if err != nil {
		log.Warningf("heartbeat to %s failed: %s", txn, err)
	}
	// TODO(bdarnell): once we have gotten a heartbeat response with
	// Status != PENDING, future heartbeats are useless. However, we
	// need to continue the heartbeatLoop until the client either
	// commits or abandons the transaction. We could save a little
	// pointless work by restructuring this loop to stop sending
	// heartbeats between the time that the transaction is aborted and
	// the client finds out. Furthermore, we could use this information
	// to send TransactionAbortedErrors to the client so it can restart
	// immediately instead of running until its EndTransaction.
	return true
}

// maybeBeginTxn begins a new transaction if a txn has been specified
// in the request but has a nil ID. The new transaction is initialized
// using the name and isolation in the otherwise uninitialized txn.
// The Priority, if non-zero is used as a minimum.
func (tc *TxnCoordSender) maybeBeginTxn(ba *roachpb.BatchRequest) {
	if ba.Txn == nil {
		return
	}
	if len(ba.Requests) == 0 {
		panic("empty batch with txn")
	}
	if len(ba.Txn.ID) == 0 {
		// TODO(tschottdorf): should really choose the first txn write here.
		firstKey := ba.Requests[0].GetInner().Header().Key
		newTxn := roachpb.NewTransaction(ba.Txn.Name, keys.KeyAddress(firstKey), ba.GetUserPriority(),
			ba.Txn.Isolation, tc.clock.Now(), tc.clock.MaxOffset().Nanoseconds())
		// Use existing priority as a minimum. This is used on transaction
		// aborts to ratchet priority when creating successor transaction.
		if newTxn.Priority < ba.Txn.Priority {
			newTxn.Priority = ba.Txn.Priority
		}
		ba.Txn = newTxn
	}
}