kv/batcheval: unify TransferLease and Subsume latching

Both of these requests want full mutual exclusion on the range, so it
makes sense that they would declare latches the same way.

pkg/keys/constants.go

@@ -42,8 +42,8 @@ var (
 	// MaxKey is the infinity marker which is larger than any other key.
 	MaxKey = roachpb.KeyMax
 
-	// localPrefix is the prefix for all local keys.
-	localPrefix = roachpb.Key{localPrefixByte}
+	// LocalPrefix is the prefix for all local keys.
+	LocalPrefix = roachpb.Key{localPrefixByte}
 	// LocalMax is the end of the local key range. It is itself a global
 	// key.
 	LocalMax = roachpb.Key{localMaxByte}
@@ -64,7 +64,7 @@ var (
 	// metadata is identified by one of the suffixes listed below, along
 	// with potentially additional encoded key info, for instance in the
 	// case of AbortSpan entry.
-	LocalRangeIDPrefix = roachpb.RKey(makeKey(localPrefix, roachpb.Key("i")))
+	LocalRangeIDPrefix = roachpb.RKey(makeKey(LocalPrefix, roachpb.Key("i")))
 	// LocalRangeIDReplicatedInfix is the post-Range ID specifier for all Raft
 	// replicated per-range data. By appending this after the Range ID, these
 	// keys will be sorted directly before the local unreplicated keys for the
@@ -134,7 +134,7 @@ var (
 	// specific sort of per-range metadata is identified by one of the
 	// suffixes listed below, along with potentially additional encoded
 	// key info, such as the txn ID in the case of a transaction record.
-	LocalRangePrefix = roachpb.Key(makeKey(localPrefix, roachpb.RKey("k")))
+	LocalRangePrefix = roachpb.Key(makeKey(LocalPrefix, roachpb.RKey("k")))
 	LocalRangeMax    = LocalRangePrefix.PrefixEnd()
 	// LocalQueueLastProcessedSuffix is the suffix for replica queue state keys.
 	LocalQueueLastProcessedSuffix = roachpb.RKey("qlpt")
@@ -161,7 +161,7 @@ var (
 	// double duty as a reference to a provisional MVCC value.
 	// TODO(sumeer): remember to adjust this comment when adding locks of
 	// other strengths, or range locks.
-	LocalRangeLockTablePrefix = roachpb.Key(makeKey(localPrefix, roachpb.RKey("l")))
+	LocalRangeLockTablePrefix = roachpb.Key(makeKey(LocalPrefix, roachpb.RKey("l")))
 	LockTableSingleKeyInfix   = []byte("k")
 	// LockTableSingleKeyStart is the inclusive start key of the key range
 	// containing single key locks.
@@ -174,7 +174,7 @@ var (
 	// 5. Store local keys
 	//
 	// localStorePrefix is the prefix identifying per-store data.
-	localStorePrefix = makeKey(localPrefix, roachpb.Key("s"))
+	localStorePrefix = makeKey(LocalPrefix, roachpb.Key("s"))
 	// localStoreSuggestedCompactionSuffix stores suggested compactions to
 	// be aggregated and processed on the store.
 	localStoreSuggestedCompactionSuffix = []byte("comp")

pkg/keys/doc.go

@@ -174,7 +174,7 @@ var _ = [...]interface{}{
 	//	  - Store keys all share `localStorePrefix`.
 	//
 	// `LocalRangeIDPrefix`, `localRangePrefix`, `LocalRangeLockTablePrefix`,
-	// and `localStorePrefix` all in turn share `localPrefix`. `localPrefix` was
+	// and `localStorePrefix` all in turn share `LocalPrefix`. `LocalPrefix` was
 	// chosen arbitrarily. Local keys would work just as well with a different
 	// prefix, like 0xff, or even with a suffix.
 

pkg/keys/keys.go

@@ -478,7 +478,7 @@ func DecodeLockTableSingleKey(key roachpb.Key) (lockedKey roachpb.Key, err error
 // opposed to "user") keys, but unfortunately that name has already been
 // claimed by a related (but not identical) concept.
 func IsLocal(k roachpb.Key) bool {
-	return bytes.HasPrefix(k, localPrefix)
+	return bytes.HasPrefix(k, LocalPrefix)
 }
 
 // IsLocalStoreKey performs a cheap check that returns true iff the parameter

pkg/keys/keys_test.go

@@ -66,7 +66,7 @@ func TestKeySorting(t *testing.T) {
 		roachpb.RKey("\x01").Less(roachpb.RKey("\x01\x00"))) {
 		t.Fatalf("something is seriously wrong with this machine")
 	}
-	if bytes.Compare(localPrefix, Meta1Prefix) >= 0 {
+	if bytes.Compare(LocalPrefix, Meta1Prefix) >= 0 {
 		t.Fatalf("local key spilling into replicated ranges")
 	}
 	if !bytes.Equal(roachpb.Key(""), roachpb.Key(nil)) {
@@ -140,7 +140,7 @@ func TestKeyAddressError(t *testing.T) {
 			RangeLastReplicaGCTimestampKey(0),
 		},
 		"local key .* malformed": {
-			makeKey(localPrefix, roachpb.Key("z")),
+			makeKey(LocalPrefix, roachpb.Key("z")),
 		},
 	}
 	for regexp, keyList := range testCases {

pkg/keys/printer.go

@@ -70,7 +70,7 @@ var (
 
 	// KeyDict drives the pretty-printing and pretty-scanning of the key space.
 	KeyDict = KeyComprehensionTable{
-		{Name: "/Local", start: localPrefix, end: LocalMax, Entries: []DictEntry{
+		{Name: "/Local", start: LocalPrefix, end: LocalMax, Entries: []DictEntry{
 			{Name: "/Store", prefix: roachpb.Key(localStorePrefix),
 				ppFunc: localStoreKeyPrint, PSFunc: localStoreKeyParse},
 			{Name: "/RangeID", prefix: roachpb.Key(LocalRangeIDPrefix),

pkg/kv/kvserver/batcheval/BUILD.bazel

@@ -92,8 +92,8 @@ go_test(
         "cmd_resolve_intent_test.go",
         "cmd_revert_range_test.go",
         "cmd_scan_test.go",
-        "cmd_subsume_test.go",
         "cmd_truncate_log_test.go",
+        "declare_test.go",
         "intent_test.go",
         "main_test.go",
         "transaction_test.go",

pkg/kv/kvserver/batcheval/cmd_lease_transfer.go

@@ -13,7 +13,6 @@ package batcheval
 import (
 	"context"
 
-	"github.com/cockroachdb/cockroach/pkg/keys"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/batcheval/result"
 	"github.com/cockroachdb/cockroach/pkg/kv/kvserver/spanset"
 	"github.com/cockroachdb/cockroach/pkg/roachpb"
@@ -28,13 +27,26 @@ func init() {
 func declareKeysTransferLease(
 	rs ImmutableRangeState, _ roachpb.Header, _ roachpb.Request, latchSpans, _ *spanset.SpanSet,
 ) {
-	latchSpans.AddNonMVCC(spanset.SpanReadWrite, roachpb.Span{Key: keys.RangeLeaseKey(rs.GetRangeID())})
-	latchSpans.AddNonMVCC(spanset.SpanReadOnly, roachpb.Span{Key: keys.RangeDescriptorKey(rs.GetStartKey())})
-	// Cover the entire addressable key space with a latch to prevent any writes
-	// from overlapping with lease transfers. In principle we could just use the
-	// current range descriptor (desc) but it could potentially change due to an
-	// as of yet unapplied merge.
-	latchSpans.AddNonMVCC(spanset.SpanReadOnly, roachpb.Span{Key: keys.LocalMax, EndKey: keys.MaxKey})
+	// TransferLease must not run concurrently with any other command so it uses
+	// latches to synchronize with all other reads and writes on the outgoing
+	// leaseholder. Additionally, it observes the state of the timestamp cache
+	// and so it uses latches to wait for all in-flight requests to complete.
+	//
+	// Because of this, it declares a non-MVCC write over every addressable key
+	// in the range, even through the only key the TransferLease actually writes
+	// to is the RangeLeaseKey. This guarantees that it conflicts with any other
+	// command because every command must declare at least one addressable key.
+	//
+	// We could, in principle, declare these latches as MVCC writes at the time
+	// of the new lease. Doing so would block all concurrent writes but would
+	// allow reads below the new lease timestamp through. However, doing so
+	// would only be safe if we also accounted for clock uncertainty in all read
+	// latches so that any read that may need to observe state on the new
+	// leaseholder gets blocked. We actually already do this for transactional
+	// reads (see DefaultDeclareIsolatedKeys), but not for non-transactional
+	// reads. We'd need to be careful here, so we should only pull on this if we
+	// decide that doing so is important.
+	declareAllKeys(latchSpans)
 }
 
 // TransferLease sets the lease holder for the range.

pkg/kv/kvserver/batcheval/cmd_subsume.go

@@ -32,27 +32,10 @@ func declareKeysSubsume(
 ) {
 	// Subsume must not run concurrently with any other command. It declares a
 	// non-MVCC write over every addressable key in the range; this guarantees
-	// that it conflicts with any other command because every command must declare
-	// at least one addressable key. It does not, in fact, write any keys.
-	//
-	// We use the key bounds from the range descriptor in the request instead
-	// of the current range descriptor. Either would be fine because we verify
-	// that these match during the evaluation of the Subsume request.
-	args := req.(*roachpb.SubsumeRequest)
-	desc := args.RightDesc
-	latchSpans.AddNonMVCC(spanset.SpanReadWrite, roachpb.Span{
-		Key:    desc.StartKey.AsRawKey(),
-		EndKey: desc.EndKey.AsRawKey(),
-	})
-	latchSpans.AddNonMVCC(spanset.SpanReadWrite, roachpb.Span{
-		Key:    keys.MakeRangeKeyPrefix(desc.StartKey),
-		EndKey: keys.MakeRangeKeyPrefix(desc.EndKey).PrefixEnd(),
-	})
-	rangeIDPrefix := keys.MakeRangeIDReplicatedPrefix(desc.RangeID)
-	latchSpans.AddNonMVCC(spanset.SpanReadWrite, roachpb.Span{
-		Key:    rangeIDPrefix,
-		EndKey: rangeIDPrefix.PrefixEnd(),
-	})
+	// that it conflicts with any other command because every command must
+	// declare at least one addressable key. It does not, in fact, write any
+	// keys.
+	declareAllKeys(latchSpans)
 }
 
 // Subsume freezes a range for merging with its left-hand neighbor. When called

pkg/kv/kvserver/batcheval/declare.go

@@ -82,6 +82,20 @@ func DeclareKeysForBatch(
 	}
 }
 
+// declareAllKeys declares a non-MVCC write over every addressable key. This
+// guarantees that the caller conflicts with any other command because every
+// command must declare at least one addressable key, which is tested against
+// in TestRequestsSerializeWithSubsume.
+func declareAllKeys(latchSpans *spanset.SpanSet) {
+	// NOTE: we don't actually know what the end key of the Range will
+	// be at the time of command evaluation (see ImmutableRangeState),
+	// so we simply declare a latch over the entire keyspace. This may
+	// extend beyond the Range, but this is ok for the purpose of
+	// acquiring latches.
+	latchSpans.AddNonMVCC(spanset.SpanReadWrite, roachpb.Span{Key: keys.LocalPrefix, EndKey: keys.LocalMax})
+	latchSpans.AddNonMVCC(spanset.SpanReadWrite, roachpb.Span{Key: keys.LocalMax, EndKey: keys.MaxKey})
+}
+
 // CommandArgs contains all the arguments to a command.
 // TODO(bdarnell): consider merging with kvserverbase.FilterArgs (which
 // would probably require removing the EvalCtx field due to import order

pkg/kv/kvserver/batcheval/cmd_subsume_test.go → pkg/kv/kvserver/batcheval/declare_test.go

@@ -21,37 +21,36 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/util/uuid"
 )
 
-// TestRequestsSerializeWithSubsume ensures that no request can be evaluated
-// concurrently with a Subsume request. For more details, refer to the big
-// comment block at the end of Subsume() in cmd_subsume.go.
-//
-// NB: This test is broader than it really needs to be. A more precise statement
-// of the condition necessary to uphold the invariant mentioned in Subsume() is:
-// No request that bumps the lease applied index of a range can be evaluated
-// concurrently with a Subsume request.
-func TestRequestsSerializeWithSubsume(t *testing.T) {
+// TestRequestsSerializeWithAllKeys ensures that no request can be evaluated
+// concurrently with either a Subsume request or a TransferLease request, both
+// of which declare latches using declareAllKeys to guarantee mutual exclusion
+// over the leaseholder.
+func TestRequestsSerializeWithAllKeys(t *testing.T) {
 	defer leaktest.AfterTest(t)()
-	var subsumeLatchSpans, subsumeLockSpans, otherLatchSpans, otherLockSpans spanset.SpanSet
-	startKey := []byte(`a`)
-	endKey := []byte(`b`)
-	desc := &roachpb.RangeDescriptor{
-		RangeID:  0,
-		StartKey: startKey,
-		EndKey:   endKey,
-	}
-	testTxn := &roachpb.Transaction{
-		TxnMeta: enginepb.TxnMeta{
-			ID:             uuid.FastMakeV4(),
-			Key:            startKey,
-			WriteTimestamp: hlc.Timestamp{WallTime: 1},
-		},
-		Name: "test txn",
-	}
-	header := roachpb.Header{Txn: testTxn}
-	subsumeRequest := &roachpb.SubsumeRequest{RightDesc: *desc}
-	declareKeysSubsume(desc, header, subsumeRequest, &subsumeLatchSpans, &subsumeLockSpans)
+
+	var allLatchSpans spanset.SpanSet
+	declareAllKeys(&allLatchSpans)
+
 	for method, command := range cmds {
 		t.Run(method.String(), func(t *testing.T) {
+			var otherLatchSpans, otherLockSpans spanset.SpanSet
+
+			startKey := []byte(`a`)
+			endKey := []byte(`b`)
+			desc := &roachpb.RangeDescriptor{
+				RangeID:  0,
+				StartKey: startKey,
+				EndKey:   endKey,
+			}
+			testTxn := &roachpb.Transaction{
+				TxnMeta: enginepb.TxnMeta{
+					ID:             uuid.FastMakeV4(),
+					Key:            startKey,
+					WriteTimestamp: hlc.Timestamp{WallTime: 1},
+				},
+				Name: "test txn",
+			}
+			header := roachpb.Header{Txn: testTxn}
 			otherRequest := roachpb.CreateRequest(method)
 			if queryTxnReq, ok := otherRequest.(*roachpb.QueryTxnRequest); ok {
 				// QueryTxnRequest declares read-only access over the txn record of the txn
@@ -60,16 +59,15 @@ func TestRequestsSerializeWithSubsume(t *testing.T) {
 				// falling outside our test range's keyspace.
 				queryTxnReq.Txn = testTxn.TxnMeta
 			}
-
 			otherRequest.SetHeader(roachpb.RequestHeader{
 				Key:      startKey,
 				EndKey:   endKey,
 				Sequence: 0,
 			})
 
 			command.DeclareKeys(desc, header, otherRequest, &otherLatchSpans, &otherLockSpans)
-			if !subsumeLatchSpans.Intersects(&otherLatchSpans) {
-				t.Errorf("%s does not serialize with Subsume", method)
+			if !allLatchSpans.Intersects(&otherLatchSpans) {
+				t.Errorf("%s does not serialize with declareAllKeys", method)
 			}
 		})
 	}

pkg/kv/kvserver/client_replica_test.go

@@ -3522,8 +3522,20 @@ func TestDiscoverIntentAcrossLeaseTransferAwayAndBack(t *testing.T) {
 		return nil
 	}
 
+	// Required by TestCluster.MoveRangeLeaseNonCooperatively.
+	knobs.AllowLeaseRequestProposalsWhenNotLeader = true
+
 	tc := testcluster.StartTestCluster(t, 3, base.TestClusterArgs{
-		ServerArgs: base.TestServerArgs{Knobs: base.TestingKnobs{Store: knobs}},
+		ServerArgs: base.TestServerArgs{Knobs: base.TestingKnobs{
+			NodeLiveness: kvserver.NodeLivenessTestingKnobs{
+				// This test waits for an epoch-based lease to expire, so we're
+				// setting the liveness duration as low as possible while still
+				// keeping the test stable.
+				LivenessDuration: 3000 * time.Millisecond,
+				RenewalDuration:  1500 * time.Millisecond,
+			},
+			Store: knobs,
+		}},
 	})
 	defer tc.Stopper().Stop(ctx)
 	kvDB := tc.Servers[0].DB()
@@ -3551,8 +3563,10 @@ func TestDiscoverIntentAcrossLeaseTransferAwayAndBack(t *testing.T) {
 	}()
 	txn2UnblockC := <-txn2BlockedC
 
-	// Transfer the lease to Server 1.
-	err = tc.TransferRangeLease(rangeDesc, tc.Target(1))
+	// Transfer the lease to Server 1. Do so non-cooperatively instead of using
+	// a lease transfer, because the cooperative lease transfer would get stuck
+	// acquiring latches, which are held by txn2.
+	err = tc.MoveRangeLeaseNonCooperatively(rangeDesc, tc.Target(1))
 	require.NoError(t, err)
 
 	// Roll back txn1.

pkg/kv/kvserver/replica_test.go

@@ -86,7 +86,7 @@ var allSpans = func() spanset.SpanSet {
 		Key:    roachpb.KeyMin,
 		EndKey: roachpb.KeyMax,
 	})
-	// Local keys (see `keys.localPrefix`).
+	// Local keys (see `keys.LocalPrefix`).
 	ss.AddNonMVCC(spanset.SpanReadWrite, roachpb.Span{
 		Key:    append([]byte("\x01"), roachpb.KeyMin...),
 		EndKey: append([]byte("\x01"), roachpb.KeyMax...),
@@ -1458,12 +1458,10 @@ func TestReplicaDrainLease(t *testing.T) {
 	// expired already.
 
 	// Stop n1's heartbeats and wait for the lease to expire.
-
 	log.Infof(ctx, "test: suspending heartbeats for n1")
 	cleanup := s1.NodeLiveness().(*liveness.NodeLiveness).PauseAllHeartbeatsForTest()
 	defer cleanup()
 
-	require.NoError(t, err)
 	testutils.SucceedsSoon(t, func() error {
 		status := r1.CurrentLeaseStatus(ctx)
 		require.True(t, status.Lease.OwnedBy(store1.StoreID()), "someone else got the lease: %s", status)