contractcourt: remove block subscription in channel arbitrator

This commit removes the block subscriptions used in `ChannelArbitrator`,
replaced them with the blockbeat managed by `BlockbeatDispatcher`.

contractcourt/channel_arbitrator.go

@@ -357,11 +357,6 @@ type ChannelArbitrator struct {
 	// to do its duty.
 	cfg ChannelArbitratorConfig
 
-	// blocks is a channel that the arbitrator will receive new blocks on.
-	// This channel should be buffered by so that it does not block the
-	// sender.
-	blocks chan int32
-
 	// signalUpdates is a channel that any new live signals for the channel
 	// we're watching over will be sent.
 	signalUpdates chan *signalUpdateMsg
@@ -411,7 +406,6 @@ func NewChannelArbitrator(cfg ChannelArbitratorConfig,
 
 	c := &ChannelArbitrator{
 		log:              log,
-		blocks:           make(chan int32, arbitratorBlockBufferSize),
 		signalUpdates:    make(chan *signalUpdateMsg),
 		resolutionSignal: make(chan struct{}),
 		forceCloseReqs:   make(chan *forceCloseReq),
@@ -2769,31 +2763,21 @@ func (c *ChannelArbitrator) channelAttendant(bestHeight int32,
 		// A new block has arrived, we'll examine all the active HTLC's
 		// to see if any of them have expired, and also update our
 		// track of the best current height.
-		case blockHeight, ok := <-c.blocks:
-			if !ok {
-				return
-			}
-			bestHeight = blockHeight
+		case beat := <-c.BlockbeatChan:
+			bestHeight = beat.Height()
 
-			// If we're not in the default state, then we can
-			// ignore this signal as we're waiting for contract
-			// resolution.
-			if c.state != StateDefault {
-				continue
-			}
+			log.Debugf("ChannelArbitrator(%v): new block height=%v",
+				c.cfg.ChanPoint, bestHeight)
 
-			// Now that a new block has arrived, we'll attempt to
-			// advance our state forward.
-			nextState, _, err := c.advanceState(
-				uint32(bestHeight), chainTrigger, nil,
-			)
+			err := c.handleBlockbeat(beat)
 			if err != nil {
-				log.Errorf("Unable to advance state: %v", err)
+				log.Errorf("Handle block=%v got err: %v",
+					bestHeight, err)
 			}
 
 			// If as a result of this trigger, the contract is
 			// fully resolved, then well exit.
-			if nextState == StateFullyResolved {
+			if c.state == StateFullyResolved {
 				return
 			}
 
@@ -3144,6 +3128,27 @@ func (c *ChannelArbitrator) channelAttendant(bestHeight int32,
 	}
 }
 
+// handleBlockbeat processes a newly received blockbeat by advancing the
+// arbitrator's internal state using the received block height.
+func (c *ChannelArbitrator) handleBlockbeat(beat chainio.Blockbeat) error {
+	// Notify we've processed the block.
+	defer c.NotifyBlockProcessed(beat, nil)
+
+	// Try to advance the state if we are in StateDefault.
+	if c.state == StateDefault {
+		// Now that a new block has arrived, we'll attempt to advance
+		// our state forward.
+		_, _, err := c.advanceState(
+			uint32(beat.Height()), chainTrigger, nil,
+		)
+		if err != nil {
+			return fmt.Errorf("unable to advance state: %w", err)
+		}
+	}
+
+	return nil
+}
+
 // Name returns a human-readable string for this subsystem.
 //
 // NOTE: Part of chainio.Consumer interface.

contractcourt/channel_arbitrator_test.go

@@ -13,6 +13,7 @@ import (
 	"github.com/btcsuite/btcd/btcutil"
 	"github.com/btcsuite/btcd/chaincfg/chainhash"
 	"github.com/btcsuite/btcd/wire"
+	"github.com/lightningnetwork/lnd/chainio"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/clock"
@@ -227,6 +228,15 @@ func (c *chanArbTestCtx) CleanUp() {
 	}
 }
 
+// receiveBlockbeat mocks the behavior of a blockbeat being sent by the
+// BlockbeatDispatcher, which essentially mocks the method `ProcessBlock`.
+func (c *chanArbTestCtx) receiveBlockbeat(height int) {
+	go func() {
+		beat := newBeatFromHeight(int32(height))
+		c.chanArb.BlockbeatChan <- beat
+	}()
+}
+
 // AssertStateTransitions asserts that the state machine steps through the
 // passed states in order.
 func (c *chanArbTestCtx) AssertStateTransitions(expectedStates ...ArbitratorState) {
@@ -1037,7 +1047,7 @@ func TestChannelArbitratorLocalForceClosePendingHtlc(t *testing.T) {
 	}
 	require.Equal(t, expectedFinalHtlcs, chanArbCtx.finalHtlcs)
 
-	// We'll no re-create the resolver, notice that we use the existing
+	// We'll now re-create the resolver, notice that we use the existing
 	// arbLog so it carries over the same on-disk state.
 	chanArbCtxNew, err := chanArbCtx.Restart(nil)
 	require.NoError(t, err, "unable to create ChannelArbitrator")
@@ -1084,7 +1094,12 @@ func TestChannelArbitratorLocalForceClosePendingHtlc(t *testing.T) {
 	}
 
 	// Send a notification that the expiry height has been reached.
+	//
+	// TODO(yy): remove the EpochChan and use the blockbeat below once
+	// resolvers are hooked with the blockbeat.
 	oldNotifier.EpochChan <- &chainntnfs.BlockEpoch{Height: 10}
+	// beat := chainio.NewBlockbeatFromHeight(10)
+	// chanArb.BlockbeatChan <- beat
 
 	// htlcOutgoingContestResolver is now transforming into a
 	// htlcTimeoutResolver and should send the contract off for incubation.
@@ -1924,7 +1939,8 @@ func TestChannelArbitratorDanglingCommitForceClose(t *testing.T) {
 			// now mine a block (height 5), which is 5 blocks away
 			// (our grace delta) from the expiry of that HTLC.
 			case testCase.htlcExpired:
-				chanArbCtx.chanArb.blocks <- 5
+				beat := newBeatFromHeight(5)
+				chanArbCtx.chanArb.BlockbeatChan <- beat
 
 			// Otherwise, we'll just trigger a regular force close
 			// request.
@@ -2036,8 +2052,7 @@ func TestChannelArbitratorDanglingCommitForceClose(t *testing.T) {
 			// so instead, we'll mine another block which'll cause
 			// it to re-examine its state and realize there're no
 			// more HTLCs.
-			chanArbCtx.chanArb.blocks <- 6
-			chanArbCtx.AssertStateTransitions(StateFullyResolved)
+			chanArbCtx.receiveBlockbeat(6)
 		})
 	}
 }
@@ -2108,13 +2123,15 @@ func TestChannelArbitratorPendingExpiredHTLC(t *testing.T) {
 	// We will advance the uptime to 10 seconds which should be still within
 	// the grace period and should not trigger going to chain.
 	testClock.SetTime(startTime.Add(time.Second * 10))
-	chanArbCtx.chanArb.blocks <- 5
+	beat := newBeatFromHeight(5)
+	chanArbCtx.chanArb.BlockbeatChan <- beat
 	chanArbCtx.AssertState(StateDefault)
 
 	// We will advance the uptime to 16 seconds which should trigger going
 	// to chain.
 	testClock.SetTime(startTime.Add(time.Second * 16))
-	chanArbCtx.chanArb.blocks <- 6
+	beat = newBeatFromHeight(6)
+	chanArbCtx.chanArb.BlockbeatChan <- beat
 	chanArbCtx.AssertStateTransitions(
 		StateBroadcastCommit,
 		StateCommitmentBroadcasted,
@@ -2482,7 +2499,7 @@ func TestSweepAnchors(t *testing.T) {
 
 	// Set current block height.
 	heightHint := uint32(1000)
-	chanArbCtx.chanArb.blocks <- int32(heightHint)
+	chanArbCtx.receiveBlockbeat(int(heightHint))
 
 	htlcIndexBase := uint64(99)
 	deadlineDelta := uint32(10)
@@ -2645,7 +2662,7 @@ func TestSweepLocalAnchor(t *testing.T) {
 
 	// Set current block height.
 	heightHint := uint32(1000)
-	chanArbCtx.chanArb.blocks <- int32(heightHint)
+	chanArbCtx.receiveBlockbeat(int(heightHint))
 
 	htlcIndex := uint64(99)
 	deadlineDelta := uint32(10)
@@ -2793,7 +2810,8 @@ func TestChannelArbitratorAnchors(t *testing.T) {
 
 	// Set current block height.
 	heightHint := uint32(1000)
-	chanArbCtx.chanArb.blocks <- int32(heightHint)
+	beat := newBeatFromHeight(int32(heightHint))
+	chanArbCtx.chanArb.BlockbeatChan <- beat
 
 	htlcAmt := lnwire.MilliSatoshi(1_000_000)
 
@@ -2960,10 +2978,14 @@ func TestChannelArbitratorAnchors(t *testing.T) {
 	// to htlcWithPreimage's CLTV.
 	require.Equal(t, 2, len(chanArbCtx.sweeper.deadlines))
 	require.EqualValues(t,
+		heightHint+deadlinePreimageDelta/2,
+		chanArbCtx.sweeper.deadlines[0], "want %d, got %d",
 		heightHint+deadlinePreimageDelta/2,
 		chanArbCtx.sweeper.deadlines[0],
 	)
 	require.EqualValues(t,
+		heightHint+deadlinePreimageDelta/2,
+		chanArbCtx.sweeper.deadlines[1], "want %d, got %d",
 		heightHint+deadlinePreimageDelta/2,
 		chanArbCtx.sweeper.deadlines[1],
 	)
@@ -3146,3 +3168,11 @@ func (m *mockChannel) ForceCloseChan() (*wire.MsgTx, error) {
 
 	return &wire.MsgTx{}, nil
 }
+
+func newBeatFromHeight(height int32) *chainio.Beat {
+	epoch := chainntnfs.BlockEpoch{
+		Height: height,
+	}
+
+	return chainio.NewBeat(epoch)
+}