kv: stop using BeginTransaction requests

Based on cockroachdb#33523.
Closes cockroachdb#25437.

This is the final part of addressing cockroachdb#32971.

The change gates the use of BeginTransaction on a cluster version.
When a cluster's version is sufficiently high, it will stop sending
them.

To make this work, a small change was needed for the detection of 1PC
transactions. We now use sequence numbers to determine that a batch
includes all of the writes in a transaction. This is in line with the
proposal from the RFC's `1PC Transactions` section and will work
correctly with parallel commits.

Release note (performance improvement): Reduce the network and storage
overhead of multi-Range transactions.

docs/RFCS/20181209_lazy_txn_record_creation.md

@@ -1,5 +1,5 @@
 - Feature Name: Lazy Transaction Record Creation (a.k.a Deprecate BeginTransaction)
-- Status: in-progress
+- Status: completed
 - Start Date: 2018-12-09
 - Authors: Nathan VanBenschoten
 - RFC PR: #32971

docs/generated/settings/settings.html

@@ -92,6 +92,6 @@
 <tr><td><code>trace.debug.enable</code></td><td>boolean</td><td><code>false</code></td><td>if set, traces for recent requests can be seen in the /debug page</td></tr>
 <tr><td><code>trace.lightstep.token</code></td><td>string</td><td><code></code></td><td>if set, traces go to Lightstep using this token</td></tr>
 <tr><td><code>trace.zipkin.collector</code></td><td>string</td><td><code></code></td><td>if set, traces go to the given Zipkin instance (example: '127.0.0.1:9411'); ignored if trace.lightstep.token is set.</td></tr>
-<tr><td><code>version</code></td><td>custom validation</td><td><code>2.1-3</code></td><td>set the active cluster version in the format '<major>.<minor>'.</td></tr>
+<tr><td><code>version</code></td><td>custom validation</td><td><code>2.1-4</code></td><td>set the active cluster version in the format '<major>.<minor>'.</td></tr>
 </tbody>
 </table>

pkg/kv/txn_coord_sender.go

@@ -417,6 +417,7 @@ func (tcf *TxnCoordSenderFactory) TransactionalSender(
 	tcs.interceptorAlloc.txnHeartbeat.init(
 		&tcs.mu.Mutex,
 		&tcs.mu.txn,
+		tcf.st,
 		tcs.clock,
 		tcs.heartbeatInterval,
 		&tcs.interceptorAlloc.txnLockGatekeeper,
@@ -581,7 +582,7 @@ func (tc *TxnCoordSender) Send(
 		return nil, pErr
 	}
 
-	if ba.IsSingleEndTransactionRequest() && !tc.interceptorAlloc.txnHeartbeat.mu.everSentBeginTxn {
+	if ba.IsSingleEndTransactionRequest() && !tc.interceptorAlloc.txnHeartbeat.mu.everWroteIntents {
 		return nil, tc.commitReadOnlyTxnLocked(ctx, ba.Requests[0].GetEndTransaction().Deadline)
 	}
 

pkg/kv/txn_coord_sender_test.go

@@ -26,6 +26,7 @@ import (
 
 	"github.com/cockroachdb/cockroach/pkg/internal/client"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
+	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
 	"github.com/cockroachdb/cockroach/pkg/storage"
 	"github.com/cockroachdb/cockroach/pkg/storage/engine"
 	"github.com/cockroachdb/cockroach/pkg/storage/engine/enginepb"
@@ -1263,13 +1264,11 @@ func TestAbortTransactionOnCommitErrors(t *testing.T) {
 				txn := ba.Txn.Clone()
 				br.Txn = &txn
 
-				if _, hasBT := ba.GetArg(roachpb.BeginTransaction); hasBT {
-					if _, ok := ba.Requests[1].GetInner().(*roachpb.PutRequest); !ok {
+				if _, hasPut := ba.GetArg(roachpb.Put); hasPut {
+					if _, ok := ba.Requests[0].GetInner().(*roachpb.PutRequest); !ok {
 						t.Fatalf("expected Put")
 					}
 					union := &br.Responses[0] // avoid operating on copy
-					union.MustSetInner(&roachpb.BeginTransactionResponse{})
-					union = &br.Responses[1] // avoid operating on copy
 					union.MustSetInner(&roachpb.PutResponse{})
 					if ba.Txn != nil && br.Txn == nil {
 						txnClone := ba.Txn.Clone()
@@ -1629,8 +1628,8 @@ func TestCommitMutatingTransaction(t *testing.T) {
 	var calls []roachpb.Method
 	sender.match(func(ba roachpb.BatchRequest) (*roachpb.BatchResponse, *roachpb.Error) {
 		calls = append(calls, ba.Methods()...)
-		if bt, ok := ba.GetArg(roachpb.BeginTransaction); ok && !bt.Header().Key.Equal(roachpb.Key("a")) {
-			t.Errorf("expected begin transaction key to be \"a\"; got %s", bt.Header().Key)
+		if !bytes.Equal(ba.Txn.Key, roachpb.Key("a")) {
+			t.Errorf("expected transaction key to be \"a\"; got %s", ba.Txn.Key)
 		}
 		if et, ok := ba.GetArg(roachpb.EndTransaction); ok && !et.(*roachpb.EndTransactionRequest).Commit {
 			t.Errorf("expected commit to be true")
@@ -1692,7 +1691,7 @@ func TestCommitMutatingTransaction(t *testing.T) {
 			if err := db.Txn(ctx, test.f); err != nil {
 				t.Fatalf("%d: unexpected error on commit: %s", i, err)
 			}
-			expectedCalls := []roachpb.Method{roachpb.BeginTransaction, test.expMethod}
+			expectedCalls := []roachpb.Method{test.expMethod}
 			if test.pointWrite {
 				expectedCalls = append(expectedCalls, roachpb.QueryIntent)
 			}
@@ -1706,6 +1705,7 @@ func TestCommitMutatingTransaction(t *testing.T) {
 
 // TestTxnInsertBeginTransaction verifies that a begin transaction
 // request is inserted just before the first mutating command.
+// TODO(nvanbenschoten): Remove in 2.3.
 func TestTxnInsertBeginTransaction(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	ctx := context.Background()
@@ -1727,9 +1727,12 @@ func TestTxnInsertBeginTransaction(t *testing.T) {
 		return nil, nil
 	})
 
+	v := cluster.VersionByKey(cluster.Version2_1)
+	st := cluster.MakeTestingClusterSettingsWithVersion(v, v)
 	factory := NewTxnCoordSenderFactory(
 		TxnCoordSenderFactoryConfig{
 			AmbientCtx: ambient,
+			Settings:   st,
 			Clock:      clock,
 			Stopper:    stopper,
 		},
@@ -1758,6 +1761,7 @@ func TestTxnInsertBeginTransaction(t *testing.T) {
 
 // TestBeginTransactionErrorIndex verifies that the error index is cleared
 // when a BeginTransaction command causes an error.
+// TODO(nvanbenschoten): Remove in 2.3.
 func TestBeginTransactionErrorIndex(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	ctx := context.Background()
@@ -1773,9 +1777,12 @@ func TestBeginTransactionErrorIndex(t *testing.T) {
 		return nil, pErr
 	})
 
+	v := cluster.VersionByKey(cluster.Version2_1)
+	st := cluster.MakeTestingClusterSettingsWithVersion(v, v)
 	factory := NewTxnCoordSenderFactory(
 		TxnCoordSenderFactoryConfig{
 			AmbientCtx: ambient,
+			Settings:   st,
 			Clock:      clock,
 			Stopper:    stopper,
 		},
@@ -1885,7 +1892,7 @@ func TestEndWriteRestartReadOnlyTransaction(t *testing.T) {
 		sender,
 	)
 	db := client.NewDB(testutils.MakeAmbientCtx(), factory, clock)
-	expCalls := []roachpb.Method{roachpb.BeginTransaction, roachpb.Put, roachpb.EndTransaction}
+	expCalls := []roachpb.Method{roachpb.Put, roachpb.EndTransaction}
 
 	testutils.RunTrueAndFalse(t, "success", func(t *testing.T, success bool) {
 		calls = nil
@@ -1911,8 +1918,8 @@ func TestEndWriteRestartReadOnlyTransaction(t *testing.T) {
 }
 
 // TestTransactionKeyNotChangedInRestart verifies that if the transaction
-// already has a key (we're in a restart), the key in the begin transaction
-// request is not changed.
+// already has a key (we're in a restart), the key in the transaction request is
+// not changed.
 func TestTransactionKeyNotChangedInRestart(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	ctx := context.Background()
@@ -1933,13 +1940,7 @@ func TestTransactionKeyNotChangedInRestart(t *testing.T) {
 			return nil, nil
 		}
 
-		// Attempt 0 should have a BeginTxnRequest, and a PutRequest.
-		// Attempt 1 should have a PutRequest.
-		if attempt == 0 {
-			if _, ok := ba.GetArg(roachpb.BeginTransaction); !ok {
-				t.Fatalf("failed to find a begin transaction request: %v", ba)
-			}
-		}
+		// Both attempts should have a PutRequest.
 		if _, ok := ba.GetArg(roachpb.Put); !ok {
 			t.Fatalf("failed to find a put request: %v", ba)
 		}
@@ -2004,9 +2005,6 @@ func TestSequenceNumbers(t *testing.T) {
 					expSequence, seq, args)
 			}
 		}
-		if expSequence != ba.Txn.Sequence {
-			t.Errorf("expected header sequence %d; got %d", expSequence, ba.Txn.Sequence)
-		}
 		br := ba.CreateReply()
 		br.Txn = ba.Txn
 		return br, nil
@@ -2081,10 +2079,9 @@ func TestConcurrentTxnRequests(t *testing.T) {
 	}
 
 	expectedCallCounts := map[roachpb.Method]int{
-		roachpb.BeginTransaction: 1,
-		roachpb.Put:              26,
-		roachpb.QueryIntent:      26,
-		roachpb.EndTransaction:   1,
+		roachpb.Put:            26,
+		roachpb.QueryIntent:    26,
+		roachpb.EndTransaction: 1,
 	}
 	if !reflect.DeepEqual(expectedCallCounts, callCounts) {
 		t.Errorf("expected %v, got %v", expectedCallCounts, callCounts)
@@ -2265,8 +2262,8 @@ func TestTxnCoordSenderPipelining(t *testing.T) {
 	}
 
 	require.Equal(t, []roachpb.Method{
-		roachpb.BeginTransaction, roachpb.Put, roachpb.QueryIntent, roachpb.EndTransaction,
-		roachpb.BeginTransaction, roachpb.Put, roachpb.EndTransaction,
+		roachpb.Put, roachpb.QueryIntent, roachpb.EndTransaction,
+		roachpb.Put, roachpb.EndTransaction,
 	}, calls)
 
 	for _, action := range []func(ctx context.Context, txn *client.Txn) error{

pkg/kv/txn_interceptor_heartbeat.go

@@ -20,6 +20,7 @@ import (
 	"time"
 
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
+	"github.com/cockroachdb/cockroach/pkg/settings/cluster"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
 	"github.com/cockroachdb/cockroach/pkg/util/log"
 	"github.com/cockroachdb/cockroach/pkg/util/stop"
@@ -50,6 +51,7 @@ type txnHeartbeat struct {
 	// sends got through `wrapped`, not directly through `gatekeeper`.
 	gatekeeper lockedSender
 
+	st                *cluster.Settings
 	clock             *hlc.Clock
 	heartbeatInterval time.Duration
 	metrics           *TxnMetrics
@@ -87,16 +89,21 @@ type txnHeartbeat struct {
 		// successful BeginTxn (in which case we know that there is a txn record)
 		// but as of May 2018 we don't do that. Note that the server accepts a
 		// BeginTxn with a higher epoch if a transaction record already exists.
+		// TODO(nvanbenschoten): Once we stop sending BeginTxn entirely (v2.3)
+		// we can get rid of this. For now, we keep it to ensure compatibility.
+		// It can't be collapsed into everWroteIntents because 2.1 nodes expect
+		// a new BeginTxn request on each epoch (e.g. to detect 1PC txns).
 		needBeginTxn bool
 
-		// everSentBeginTxn is set once a BeginTransactionRequest (out of possibly
-		// many) was sent to the server. If a BeginTxn was ever sent, then an
-		// EndTransaction needs to eventually be sent and cannot be elided.
-		// Note that simply looking at txnEnd == nil to see if a heartbeat loop is
-		// currently running is not always sufficient for deciding whether an
-		// EndTransaction can be elided - we want to allow multiple rollback attempts
-		// to be sent and the first one stops the heartbeat loop.
-		everSentBeginTxn bool
+		// everWroteIntents is set once the transaction's first write is sent to
+		// the server. If a write was ever sent, then an EndTransaction needs to
+		// eventually be sent and cannot be elided. Note that simply looking at
+		// txnEnd == nil to see if a heartbeat loop is currently running is not
+		// always sufficient for deciding whether an EndTransaction can be
+		// elided - we want to allow multiple rollback attempts to be sent and
+		// the first one stops the heartbeat loop.
+		// TODO(nvanbenschoten): Can this be replaced with h.mu.txn.Writing?
+		everWroteIntents bool
 	}
 }
 
@@ -105,6 +112,7 @@ type txnHeartbeat struct {
 func (h *txnHeartbeat) init(
 	mu sync.Locker,
 	txn *roachpb.Transaction,
+	st *cluster.Settings,
 	clock *hlc.Clock,
 	heartbeatInterval time.Duration,
 	gatekeeper lockedSender,
@@ -113,6 +121,7 @@ func (h *txnHeartbeat) init(
 	asyncAbortCallbackLocked func(context.Context),
 ) {
 	h.stopper = stopper
+	h.st = st
 	h.clock = clock
 	h.heartbeatInterval = heartbeatInterval
 	h.metrics = metrics
@@ -147,10 +156,11 @@ func (h *txnHeartbeat) SendLocked(
 		etReq = et.(*roachpb.EndTransactionRequest)
 	}
 
+	addedBeginTxn := false
 	needBeginTxn := haveTxnWrite && h.mu.needBeginTxn
 	if needBeginTxn {
 		h.mu.needBeginTxn = false
-		h.mu.everSentBeginTxn = true
+		h.mu.everWroteIntents = true
 		// From now on, all requests need to be checked against the AbortCache on
 		// the server side. We also conservatively update the current request,
 		// although I'm not sure if that's necessary.
@@ -167,20 +177,25 @@ func (h *txnHeartbeat) SendLocked(
 			// prepared before we had an anchor.
 			ba.Txn.Key = anchor
 		}
-		// Set the key in the begin transaction request to the txn's anchor key.
-		bt := &roachpb.BeginTransactionRequest{
-			RequestHeader: roachpb.RequestHeader{
-				Key: h.mu.txn.Key,
-			},
-		}
 
-		// Inject the new request before the first write position, taking care to
-		// avoid unnecessary allocations.
-		oldRequests := ba.Requests
-		ba.Requests = make([]roachpb.RequestUnion, len(ba.Requests)+1)
-		copy(ba.Requests, oldRequests[:firstWriteIdx])
-		ba.Requests[firstWriteIdx].MustSetInner(bt)
-		copy(ba.Requests[firstWriteIdx+1:], oldRequests[firstWriteIdx:])
+		if !h.st.Version.IsActive(cluster.VersionLazyTxnRecord) {
+			addedBeginTxn = true
+
+			// Set the key in the begin transaction request to the txn's anchor key.
+			bt := &roachpb.BeginTransactionRequest{
+				RequestHeader: roachpb.RequestHeader{
+					Key: h.mu.txn.Key,
+				},
+			}
+
+			// Inject the new request before the first write position, taking care to
+			// avoid unnecessary allocations.
+			oldRequests := ba.Requests
+			ba.Requests = make([]roachpb.RequestUnion, len(ba.Requests)+1)
+			copy(ba.Requests, oldRequests[:firstWriteIdx])
+			ba.Requests[firstWriteIdx].MustSetInner(bt)
+			copy(ba.Requests[firstWriteIdx+1:], oldRequests[firstWriteIdx:])
+		}
 
 		// Start the heartbeat loop.
 		// Note that we don't do it for 1PC txns: they only leave intents around on
@@ -204,7 +219,7 @@ func (h *txnHeartbeat) SendLocked(
 	var commitTurnedToRollback bool
 	if haveEndTxn {
 		// Are we writing now or have we written in the past?
-		elideEndTxn = !h.mu.everSentBeginTxn
+		elideEndTxn = !h.mu.everWroteIntents
 		if elideEndTxn {
 			ba.Requests = ba.Requests[:lastIndex]
 		} else if etReq.Commit {
@@ -234,7 +249,7 @@ func (h *txnHeartbeat) SendLocked(
 	}
 
 	// If we inserted a begin transaction request, remove it here.
-	if needBeginTxn {
+	if addedBeginTxn {
 		if br != nil && br.Responses != nil {
 			br.Responses = append(br.Responses[:firstWriteIdx], br.Responses[firstWriteIdx+1:]...)
 		}
@@ -466,6 +481,16 @@ func (h *txnHeartbeat) heartbeat(ctx context.Context) bool {
 			return true
 		}
 
+		// TODO(nvanbenschoten): Figure out what to do here. The case we're
+		// handling is TransactionAbortedErrors without corresponding
+		// transaction protos attached.
+		if _, ok := pErr.GetDetail().(*roachpb.TransactionAbortedError); ok {
+			h.mu.txn.Status = roachpb.ABORTED
+			log.VEventf(ctx, 1, "Heartbeat detected aborted txn. Cleaning up.")
+			h.abortTxnAsyncLocked(ctx)
+			return false
+		}
+
 		respTxn = pErr.GetTxn()
 	} else {
 		respTxn = br.Responses[0].GetInner().(*roachpb.HeartbeatTxnResponse).Txn

pkg/kv/txn_interceptor_metrics.go

@@ -47,9 +47,7 @@ func (m *txnMetrics) init(txn *roachpb.Transaction, clock *hlc.Clock, metrics *T
 func (m *txnMetrics) SendLocked(
 	ctx context.Context, ba roachpb.BatchRequest,
 ) (*roachpb.BatchResponse, *roachpb.Error) {
-	_, hasBegin := ba.GetArg(roachpb.BeginTransaction)
-	et, hasEnd := ba.GetArg(roachpb.EndTransaction)
-	m.onePCCommit = hasBegin && hasEnd && et.(*roachpb.EndTransactionRequest).Commit
+	m.onePCCommit = ba.IsCompleteTransaction()
 
 	if m.txnStartNanos == 0 {
 		m.txnStartNanos = timeutil.Now().UnixNano()

pkg/kv/txn_interceptor_pipeliner.go

@@ -154,9 +154,7 @@ func (tp *txnPipeliner) SendLocked(
 	ctx context.Context, ba roachpb.BatchRequest,
 ) (*roachpb.BatchResponse, *roachpb.Error) {
 	// Fast-path for 1PC transactions.
-	_, hasBT := ba.GetArg(roachpb.BeginTransaction)
-	_, hasET := ba.GetArg(roachpb.EndTransaction)
-	if hasBT && hasET {
+	if ba.IsCompleteTransaction() {
 		return tp.wrapped.SendLocked(ctx, ba)
 	}