Golang BatchRequest.Txn方法代码示例

// 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(123)
	clock := hlc.NewClock(manual.UnixNano, 20*time.Nanosecond)

	senderFunc := func(_ context.Context, ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
		br := ba.CreateReply()
		txnClone := ba.Txn.Clone()
		br.Txn = &txnClone
		br.Txn.Writing = true
		return br, nil
	}
	ambient := log.AmbientContext{Tracer: tracing.NewTracer()}
	ts := NewTxnCoordSender(
		ambient, senderFn(senderFunc), clock, false, stopper, MakeTxnMetrics(metric.TestSampleInterval),
	)

	// 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)
	}
}

// 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
			}
			ambient := log.AmbientContext{Tracer: tracing.NewTracer()}
			ts := NewTxnCoordSender(
				ambient,
				senderFn(senderFunc),
				clock,
				false,
				stopper,
				MakeTxnMetrics(metric.TestSampleInterval),
			)

			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 TestBatchRequestString(t *testing.T) {
	br := roachpb.BatchRequest{}
	br.Txn = new(roachpb.Transaction)
	for i := 0; i < 100; i++ {
		br.Requests = append(br.Requests, roachpb.RequestUnion{Get: &roachpb.GetRequest{}})
	}
	br.Requests = append(br.Requests, roachpb.RequestUnion{EndTransaction: &roachpb.EndTransactionRequest{}})

	e := `[txn: <nil>], Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), ... 76 skipped ..., Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), Get [/Min,/Min), EndTransaction [/Min,/Min)`
	if e != br.String() {
		t.Fatalf("e = %s, v = %s", e, br.String())
	}
}

// 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) {
	// 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 {
		rs, err := keys.Range(ba)
		if err != nil {
			return nil, roachpb.NewError(err)
		}
		rangeID, repDesc, err := ls.LookupReplica(rs.Key, rs.EndKey)
		if err != nil {
			return nil, roachpb.NewError(err)
		}
		ba.RangeID = rangeID
		ba.Replica = repDesc
	}

	store, err := ls.GetStore(ba.Replica.StoreID)
	if err != nil {
		return nil, roachpb.NewError(err)
	}

	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) {
				log.Event(ctx, "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
}

// 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 len(ba.Requests) == 0 {
		return errors.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 == hlc.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 errors.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 errors.Errorf("transactional write before begin transaction")
		}
	}
	return nil
}

// 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.
	intentSpans, _ := roachpb.MergeSpans(append([]roachpb.Span(nil), 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)
	ctx := tc.AnnotateCtx(context.TODO())
	if err := tc.stopper.RunAsyncTask(ctx, func(ctx context.Context) {
		// Use the wrapped sender since the normal Sender does not allow
		// clients to specify intents.
		if _, pErr := tc.wrapped.Send(ctx, ba); pErr != nil {
			if log.V(1) {
				log.Warningf(ctx, "abort due to inactivity failed for %s: %s ", txn, pErr)
			}
		}
	}); err != nil {
		log.Warning(ctx, err)
	}
}

// TestTxnCoordSenderHeartbeat verifies periodic heartbeat of the
// transaction record.
func TestTxnCoordSenderHeartbeat(t *testing.T) {
	defer leaktest.AfterTest(t)()
	s, sender := createTestDB(t)
	defer s.Stop()
	defer teardownHeartbeats(sender)

	// Set heartbeat interval to 1ms for testing.
	sender.heartbeatInterval = 1 * time.Millisecond

	initialTxn := client.NewTxn(context.Background(), *s.DB)
	if err := initialTxn.Put(roachpb.Key("a"), []byte("value")); err != nil {
		t.Fatal(err)
	}

	// Verify 3 heartbeats.
	var heartbeatTS hlc.Timestamp
	for i := 0; i < 3; i++ {
		util.SucceedsSoon(t, func() error {
			txn, pErr := getTxn(sender, &initialTxn.Proto)
			if pErr != nil {
				t.Fatal(pErr)
			}
			// Advance clock by 1ns.
			// Locking the TxnCoordSender to prevent a data race.
			sender.Lock()
			s.Manual.Increment(1)
			sender.Unlock()
			if txn.LastHeartbeat != nil && heartbeatTS.Less(*txn.LastHeartbeat) {
				heartbeatTS = *txn.LastHeartbeat
				return nil
			}
			return errors.Errorf("expected heartbeat")
		})
	}

	// Sneakily send an ABORT right to DistSender (bypassing TxnCoordSender).
	{
		var ba roachpb.BatchRequest
		ba.Add(&roachpb.EndTransactionRequest{
			Commit: false,
			Span:   roachpb.Span{Key: initialTxn.Proto.Key},
		})
		ba.Txn = &initialTxn.Proto
		if _, pErr := sender.wrapped.Send(context.Background(), ba); pErr != nil {
			t.Fatal(pErr)
		}
	}

	util.SucceedsSoon(t, func() error {
		sender.Lock()
		defer sender.Unlock()
		if txnMeta, ok := sender.txns[*initialTxn.Proto.ID]; !ok {
			t.Fatal("transaction unregistered prematurely")
		} else if txnMeta.txn.Status != roachpb.ABORTED {
			return fmt.Errorf("transaction is not aborted")
		}
		return nil
	})

	// Trying to do something else should give us a TransactionAbortedError.
	_, err := initialTxn.Get("a")
	assertTransactionAbortedError(t, err)
}

// divideAndSendBatchToRanges sends the supplied batch to all of the
// ranges which comprise the span specified by rs. The batch request
// is trimmed against each range which is part of the span and sent
// either serially or in parallel, if possible. isFirst indicates
// whether this is the first time this method has been called on the
// batch. It's specified false where this method is invoked recursively.
func (ds *DistSender) divideAndSendBatchToRanges(
	ctx context.Context, ba roachpb.BatchRequest, rs roachpb.RSpan, isFirst bool,
) (br *roachpb.BatchResponse, pErr *roachpb.Error) {
	// This function builds a channel of responses for each range
	// implicated in the span (rs) and combines them into a single
	// BatchResponse when finished.
	var responseChs []chan response
	defer func() {
		for _, responseCh := range responseChs {
			resp := <-responseCh
			if resp.pErr != nil {
				if pErr == nil {
					pErr = resp.pErr
				}
				continue
			}
			if br == nil {
				// First response from a Range.
				br = resp.reply
			} else {
				// This was the second or later call in a cross-Range request.
				// Combine the new response with the existing one.
				if err := br.Combine(resp.reply); err != nil {
					pErr = roachpb.NewError(err)
					return
				}
				br.Txn.Update(resp.reply.Txn)
			}
		}

		// If we experienced an error, don't neglect to update the error's
		// attached transaction with any responses which were received.
		if pErr != nil {
			if br != nil {
				pErr.UpdateTxn(br.Txn)
			}
		}
	}()

	// Get initial seek key depending on direction of iteration.
	var seekKey roachpb.RKey
	isReverse := ba.IsReverse()
	if isReverse {
		seekKey = rs.EndKey
	} else {
		seekKey = rs.Key
	}
	// Send the request to one range per iteration.
	ri := NewRangeIterator(ds, isReverse)
	for ri.Seek(ctx, seekKey); ri.Valid(); ri.Seek(ctx, seekKey) {
		// Increase the sequence counter only once before sending RPCs to
		// the ranges involved in this chunk of the batch (as opposed to
		// for each RPC individually). On RPC errors, there's no guarantee
		// that the request hasn't made its way to the target regardless
		// of the error; we'd like the second execution to be caught by
		// the sequence cache if that happens. There is a small chance
		// that we address a range twice in this chunk (stale/suboptimal
		// descriptors due to splits/merges) which leads to a transaction
		// retry.
		//
		// TODO(tschottdorf): it's possible that if we don't evict from
		// the cache we could be in for a busy loop.
		ba.SetNewRequest()

		responseCh := make(chan response, 1)
		responseChs = append(responseChs, responseCh)

		if isFirst && ri.NeedAnother(rs) {
			// TODO(tschottdorf): we should have a mechanism for discovering
			// range merges (descriptor staleness will mostly go unnoticed),
			// or we'll be turning single-range queries into multi-range
			// queries for no good reason.
			//
			// If there's no transaction and op spans ranges, possibly
			// re-run as part of a transaction for consistency. The
			// case where we don't need to re-run is if the read
			// consistency is not required.
			if ba.Txn == nil && ba.IsPossibleTransaction() && ba.ReadConsistency != roachpb.INCONSISTENT {
				responseCh <- response{pErr: roachpb.NewError(&roachpb.OpRequiresTxnError{})}
				return
			}
			// If the request is more than but ends with EndTransaction, we
			// want the caller to come again with the EndTransaction in an
			// extra call.
			if l := len(ba.Requests) - 1; l > 0 && ba.Requests[l].GetInner().Method() == roachpb.EndTransaction {
				responseCh <- response{pErr: errNo1PCTxn}
				return
			}
		}

		// Determine next seek key, taking a potentially sparse batch into
		// consideration.
		var err error
		nextRS := rs
//.........这里部分代码省略.........

// initAndVerifyBatch initializes timestamp-related information and
// verifies batch constraints before splitting.
func (ds *DistSender) initAndVerifyBatch(
	ctx context.Context, ba *roachpb.BatchRequest,
) *roachpb.Error {
	// In the event that timestamp isn't set and read consistency isn't
	// required, set the timestamp using the local clock.
	if ba.ReadConsistency == roachpb.INCONSISTENT && ba.Timestamp.Equal(hlc.ZeroTimestamp) {
		ba.Timestamp = ds.clock.Now()
	}

	if ba.Txn != nil {
		// Make a copy here since the code below modifies it in different places.
		// TODO(tschottdorf): be smarter about this - no need to do it for
		// requests that don't get split.
		txnClone := ba.Txn.Clone()
		ba.Txn = &txnClone

		if len(ba.Txn.ObservedTimestamps) == 0 {
			// Ensure the local NodeID is marked as free from clock offset;
			// the transaction's timestamp was taken off the local clock.
			if nDesc := ds.getNodeDescriptor(); nDesc != nil {
				// TODO(tschottdorf): future refactoring should move this to txn
				// creation in TxnCoordSender, which is currently unaware of the
				// NodeID (and wraps *DistSender through client.Sender since it
				// also needs test compatibility with *LocalSender).
				//
				// Taking care below to not modify any memory referenced from
				// our BatchRequest which may be shared with others.
				//
				// We already have a clone of our txn (see above), so we can
				// modify it freely.
				//
				// Zero the existing data. That makes sure that if we had
				// something of size zero but with capacity, we don't re-use the
				// existing space (which others may also use). This is just to
				// satisfy paranoia/OCD and not expected to matter in practice.
				ba.Txn.ResetObservedTimestamps()
				// OrigTimestamp is the HLC timestamp at which the Txn started, so
				// this effectively means no more uncertainty on this node.
				ba.Txn.UpdateObservedTimestamp(nDesc.NodeID, ba.Txn.OrigTimestamp)
			}
		}
	}

	if len(ba.Requests) < 1 {
		return roachpb.NewErrorf("empty batch")
	}

	if ba.MaxSpanRequestKeys != 0 {
		// Verify that the batch contains only specific range requests or the
		// Begin/EndTransactionRequest. Verify that a batch with a ReverseScan
		// only contains ReverseScan range requests.
		isReverse := ba.IsReverse()
		for _, req := range ba.Requests {
			inner := req.GetInner()
			switch inner.(type) {
			case *roachpb.ScanRequest, *roachpb.DeleteRangeRequest:
				// Accepted range requests. All other range requests are still
				// not supported.
				// TODO(vivek): don't enumerate all range requests.
				if isReverse {
					return roachpb.NewErrorf("batch with limit contains both forward and reverse scans")
				}

			case *roachpb.BeginTransactionRequest, *roachpb.EndTransactionRequest, *roachpb.ReverseScanRequest:
				continue

			default:
				return roachpb.NewErrorf("batch with limit contains %T request", inner)
			}
		}
	}

	return nil
}

// sendInternal sends the batch and updates the transaction on error. Depending
// on the error type, the transaction might be replaced by a new one.
func (txn *Txn) sendInternal(ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
	if len(ba.Requests) == 0 {
		return nil, nil
	}
	if pErr := txn.db.prepareToSend(&ba); pErr != nil {
		return nil, pErr
	}

	// Send call through the DB's sender.
	ba.Txn = &txn.Proto
	// For testing purposes, txn.UserPriority can be a negative value (see
	// MakePriority).
	if txn.UserPriority != 0 {
		ba.UserPriority = txn.UserPriority
	}

	// TODO(radu): when db.send supports a context, we can just use that (and
	// remove the prepareToSend call above).
	br, pErr := txn.db.sender.Send(txn.Context, ba)
	if br != nil && br.Error != nil {
		panic(roachpb.ErrorUnexpectedlySet(txn.db.sender, 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)
			}
			txn.CollectedSpans = append(txn.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 {
		txn.Proto.Update(br.Txn)
		return br, nil
	}

	if log.V(1) {
		log.Infof(txn.Context, "failed batch: %s", pErr)
	}

	if _, ok := pErr.GetDetail().(*roachpb.TransactionAbortedError); ok {
		// On Abort, reset the transaction so we start anew on restart.
		txn.Proto = roachpb.Transaction{
			TxnMeta: enginepb.TxnMeta{
				Isolation: txn.Proto.Isolation,
			},
			Name: txn.Proto.Name,
		}
		// Acts as a minimum priority on restart.
		if pErr.GetTxn() != nil {
			txn.Proto.Priority = pErr.GetTxn().Priority
		}
	} else if pErr.TransactionRestart != roachpb.TransactionRestart_NONE {
		txn.Proto.Update(pErr.GetTxn())
	}
	return nil, pErr
}

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

	if txn.Status != roachpb.PENDING {
		// A previous iteration has already determined that the transaction is
		// already finalized, so we wait for the client to realize that and
		// want to keep our state for the time being (to dish out the right
		// error once it returns).
		return true
	}

	// 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.
	//
	// TODO(andrei): We should disallow non-cancellable contexts in the heartbeat
	// goroutine and enforce that our kv client cancels the context when it's
	// done. We get non-cancellable contexts from remote clients
	// (roachpb.ExternalClient) because we override the gRPC context to make it
	// non-cancellable in DBServer.Batch (as that context is not tied to a txn
	// lifetime).
	// Further note that, unfortunately, the Sender interface generally makes it
	// difficult for the TxnCoordSender to get a context with the same lifetime as
	// the transaction (the TxnCoordSender associates the context of the txn's
	// first write with the txn). We should move to using only use local clients
	// (i.e. merge, or at least co-locate client.Txn and the TxnCoordSender). At
	// that point, we probably don't even need to deal with context cancellation
	// any more; the client will be trusted to always send an EndRequest when it's
	// done with a transaction.
	if ctx.Done() == nil && hasAbandoned {
		if log.V(1) {
			log.Infof(ctx, "transaction %s abandoned; stopping heartbeat", txnMeta.txn)
		}
		tc.tryAsyncAbort(txnID)
		return false
	}

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

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

	log.Event(ctx, "heartbeat")
	br, pErr := tc.wrapped.Send(ctx, ba)

	// Correctness mandates that when we can't heartbeat the transaction, we
	// make sure the client doesn't keep going. This is particularly relevant
	// in the case of an ABORTED transaction, but if we can't reach the
	// transaction record at all, we're going to have to assume we're aborted
	// as well.
	if pErr != nil {
		log.Warningf(ctx, "heartbeat to %s failed: %s", txn, pErr)
		// We're not going to let the client carry out additional requests, so
		// try to clean up.
		tc.tryAsyncAbort(*txn.ID)
		txn.Status = roachpb.ABORTED
	} else {
		txn.Update(br.Responses[0].GetInner().(*roachpb.HeartbeatTxnResponse).Txn)
	}

	// Give the news to the txn in the txns map. This will update long-running
	// transactions (which may find out that they have to restart in that way),
	// but in particular makes sure that they notice when they've been aborted
	// (in which case we'll give them an error on their next request).
	tc.Lock()
	tc.txns[txnID].txn.Update(&txn)
	tc.Unlock()

	return true
}

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

	if txn.Status != roachpb.PENDING {
		// A previous iteration has already determined that the transaction is
		// already finalized, so we wait for the client to realize that and
		// want to keep our state for the time being (to dish out the right
		// error once it returns).
		return true
	}

	// 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 cancelable Context and we skip this check and use the ctx lifetime
	// instead of a timeout.
	if ctx.Done() == nil && hasAbandoned {
		if log.V(1) {
			log.Infof(ctx, "transaction %s abandoned; stopping heartbeat", txnMeta.txn)
		}
		tc.tryAsyncAbort(txnID)
		return false
	}

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

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

	log.Event(ctx, "heartbeat")
	br, pErr := tc.wrapped.Send(ctx, ba)

	// Correctness mandates that when we can't heartbeat the transaction, we
	// make sure the client doesn't keep going. This is particularly relevant
	// in the case of an ABORTED transaction, but if we can't reach the
	// transaction record at all, we're going to have to assume we're aborted
	// as well.
	if pErr != nil {
		log.Warningf(ctx, "heartbeat to %s failed: %s", txn, pErr)
		// We're not going to let the client carry out additional requests, so
		// try to clean up.
		tc.tryAsyncAbort(*txn.ID)
		txn.Status = roachpb.ABORTED
	} else {
		txn.Update(br.Responses[0].GetInner().(*roachpb.HeartbeatTxnResponse).Txn)
	}

	// Give the news to the txn in the txns map. This will update long-running
	// transactions (which may find out that they have to restart in that way),
	// but in particular makes sure that they notice when they've been aborted
	// (in which case we'll give them an error on their next request).
	tc.Lock()
	tc.txns[txnID].txn.Update(&txn)
	tc.Unlock()

	return true
}