contractcourt: integrate notifications of the chainWatcher with each channel arb

In this commit, we modify the construction of the channel arbitrator to
accept a pointer to an event stream from the chain watcher that’s been
assigned to that channel. As a result, we no longer need a fresh
unilateral close signal, as the one we get from the chain watcher will
*always* be up to date.

For each active channel, we’ll now create a chainWatcher instance that
will be around until the channel is fully closed on chain.

contractcourt/chain_arbitrator.go

@@ -130,6 +130,10 @@ type ChainArbitrator struct {
 	// open, and not fully resolved.
 	activeChannels map[wire.OutPoint]*ChannelArbitrator
 
+	// activeWatchers is a map of all the active chainWatchers for channels
+	// that are still considered open.
+	activeWatchers map[wire.OutPoint]*chainWatcher
+
 	// cfg is the config struct for the arbitrator that contains all
 	// methods and interface it needs to operate.
 	cfg ChainArbitratorConfig
@@ -151,6 +155,7 @@ func NewChainArbitrator(cfg ChainArbitratorConfig,
 	return &ChainArbitrator{
 		cfg:            cfg,
 		activeChannels: make(map[wire.OutPoint]*ChannelArbitrator),
+		activeWatchers: make(map[wire.OutPoint]*chainWatcher),
 		chanSource:     db,
 		quit:           make(chan struct{}),
 	}
@@ -159,7 +164,7 @@ func NewChainArbitrator(cfg ChainArbitratorConfig,
 // newActiveChannelArbitrator creates a new instance of an active channel
 // arbitrator given the state of the target channel.
 func newActiveChannelArbitrator(channel *channeldb.OpenChannel,
-	c *ChainArbitrator) (*ChannelArbitrator, error) {
+	c *ChainArbitrator, chanEvents *ChainEventSubscription) (*ChannelArbitrator, error) {
 
 	log.Tracef("Creating ChannelArbitrator for ChannelPoint(%v)",
 		channel.FundingOutpoint)
@@ -208,12 +213,11 @@ func newActiveChannelArbitrator(channel *channeldb.OpenChannel,
 			}
 
 			chanMachine, err := lnwallet.NewLightningChannel(
-				c.cfg.Signer, nil, c.cfg.PreimageDB, channel)
+				c.cfg.Signer, c.cfg.PreimageDB, channel)
 			if err != nil {
 				return nil, err
 			}
 			chanMachine.Stop()
-			chanMachine.CancelObserver()
 
 			if err := c.cfg.MarkLinkInactive(chanPoint); err != nil {
 				log.Errorf("unable to mark link inactive: %v", err)
@@ -228,6 +232,7 @@ func newActiveChannelArbitrator(channel *channeldb.OpenChannel,
 			return channel.CloseChannel(summary)
 		},
 		ChainArbitratorConfig: c.cfg,
+		ChainEvents:           chanEvents,
 	}
 
 	// The final component needed is an arbitrator log that the arbitrator
@@ -307,7 +312,19 @@ func (c *ChainArbitrator) Start() error {
 	// For each open channel, we'll configure then launch a corresponding
 	// ChannelArbitrator.
 	for _, channel := range openChannels {
-		channelArb, err := newActiveChannelArbitrator(channel, c)
+		// First, we'll create an active chainWatcher for this channel
+		// to ensure that we detect any relevant on chain events.
+		chainWatcher, err := newChainWatcher(
+			channel, c.cfg.Notifier, c.cfg.PreimageDB, c.cfg.Signer,
+		)
+		if err != nil {
+			return err
+		}
+
+		c.activeWatchers[channel.FundingOutpoint] = chainWatcher
+		channelArb, err := newActiveChannelArbitrator(
+			channel, c, chainWatcher.SubscribeChannelEvents(),
+		)
 		if err != nil {
 			return err
 		}
@@ -344,6 +361,7 @@ func (c *ChainArbitrator) Start() error {
 			ShortChanID:           closeChanInfo.ShortChanID,
 			BlockEpochs:           blockEpoch,
 			ChainArbitratorConfig: c.cfg,
+			ChainEvents:           &ChainEventSubscription{},
 		}
 		chanLog, err := newBoltArbitratorLog(
 			c.chanSource.DB, arbCfg, c.cfg.ChainHash, chanPoint,
@@ -363,8 +381,13 @@ func (c *ChainArbitrator) Start() error {
 		)
 	}
 
-	// Finally, we'll launch all the goroutines for each arbitrator so they
-	// can carry out their duties.
+	// Finally, we'll launch all the goroutines for each watcher and
+	// arbitrator so they can carry out their duties.
+	for _, watcher := range c.activeWatchers {
+		if err := watcher.Start(); err != nil {
+			return err
+		}
+	}
 	for _, arbitrator := range c.activeChannels {
 		if err := arbitrator.Start(); err != nil {
 			return err
@@ -390,8 +413,18 @@ func (c *ChainArbitrator) Stop() error {
 
 	c.Lock()
 	arbitrators := c.activeChannels
+	watchers := c.activeWatchers
 	c.Unlock()
 
+	for chanPoint, watcher := range watchers {
+		log.Tracef("Attempting to stop ChainWatcher(%v)",
+			chanPoint)
+
+		if err := watcher.Stop(); err != nil {
+			log.Errorf("unable to stop watcher for "+
+				"ChannelPoint(%v): %v", chanPoint, err)
+		}
+	}
 	for chanPoint, arbitrator := range arbitrators {
 		log.Tracef("Attempting to stop ChannelArbitrator(%v)",
 			chanPoint)
@@ -417,14 +450,6 @@ type ContractSignals struct {
 	// be sent over.
 	HtlcUpdates chan []channeldb.HTLC
 
-	// UniCloseSignal is a channel that allows the ChannelArbitrator for a
-	// particular channel to detect if the remote party has broadcast their
-	// version of the commitment transaction.
-	//
-	// TODO(roasbeef): eliminate and just roll into the struct itself, all
-	// watching
-	UniCloseSignal chan *lnwallet.UnilateralCloseSummary
-
 	// ShortChanID is the up to date short channel ID for a contract. This
 	// can change either if when the contract was added it didn't yet have
 	// a stable identifier, or in the case of a reorg.
@@ -452,17 +477,17 @@ func (c *ChainArbitrator) UpdateContractSignals(chanPoint wire.OutPoint,
 	return nil
 }
 
-// forceCloseReq is a request sent from an outsde sub-system to the arbitrator
-// that watches a particular channel to broadcast the commitnet transaction,
+// forceCloseReq is a request sent from an outside sub-system to the arbitrator
+// that watches a particular channel to broadcast the commitment transaction,
 // and enter the resolution phase of the channel.
 type forceCloseReq struct {
-	// errResp is a channel that will be sent upon either in the case of force
-	// close success (nil error), or in the case on an erro (nil-nil error)
+	// errResp is a channel that will be sent upon either in the case of
+	// force close success (nil error), or in the case on an error.
 	//
 	// NOTE; This channel MUST be buffered.
 	errResp chan error
 
-	// closeTx is a channel that carries the transaction which ultimatley
+	// closeTx is a channel that carries the transaction which ultimately
 	// closed out the channel.
 	closeTx chan *wire.MsgTx
 }
@@ -497,7 +522,7 @@ func (c *ChainArbitrator) ForceCloseContract(chanPoint wire.OutPoint) (*wire.Msg
 		return nil, fmt.Errorf("ChainArbitrator shutting down")
 	}
 
-	// We'll await two resposnes: the error response, and the transaction
+	// We'll await two responses: the error response, and the transaction
 	// that closed out the channel.
 	select {
 	case err := <-errChan:
@@ -518,11 +543,11 @@ func (c *ChainArbitrator) ForceCloseContract(chanPoint wire.OutPoint) (*wire.Msg
 	return closeTx, nil
 }
 
-// RequestChannelArbitration sends the ChainArbitrator a message to create a
+// WatchNewChannel sends the ChainArbitrator a message to create a
 // ChannelArbitrator tasked with watching over a new channel. Once a new
 // channel has finished its final funding flow, it should be registered with
 // the ChainArbitrator so we can properly react to any on-chain events.
-func (c *ChainArbitrator) RequestChannelArbitration(newChan *channeldb.OpenChannel) error {
+func (c *ChainArbitrator) WatchNewChannel(newChan *channeldb.OpenChannel) error {
 	c.Lock()
 	defer c.Unlock()
 
@@ -536,9 +561,22 @@ func (c *ChainArbitrator) RequestChannelArbitration(newChan *channeldb.OpenChann
 		return nil
 	}
 
-	// First, we'll create a new channel arbitrator instance using this new
+	// First, also create an active chainWatcher for this channel to ensure
+	// that we detect any relevant on chain events.
+	chainWatcher, err := newChainWatcher(
+		newChan, c.cfg.Notifier, c.cfg.PreimageDB, c.cfg.Signer,
+	)
+	if err != nil {
+		return err
+	}
+
+	c.activeWatchers[newChan.FundingOutpoint] = chainWatcher
+
+	// We'll also create a new channel arbitrator instance using this new
 	// channel, and our internal state.
-	channelArb, err := newActiveChannelArbitrator(newChan, c)
+	channelArb, err := newActiveChannelArbitrator(
+		newChan, c, chainWatcher.SubscribeChannelEvents(),
+	)
 	if err != nil {
 		return err
 	}
@@ -567,12 +605,14 @@ func (c *ChainArbitrator) ManuallyResolveChannel(chanPoint wire.OutPoint) error
 	}
 
 	if err := channelArb.Stop(); err != nil {
+	if err := channelArb.Start(); err != nil {
 		return err
 	}
 
 	delete(c.activeChannels, chanPoint)
 
 	return channelArb.log.WipeHistory()
+	return chainWatcher.Start()
 }
 
 // SubscribeChannelSignals...

contractcourt/channel_arbitrator.go

@@ -80,6 +80,11 @@ type ChannelArbitratorConfig struct {
 	// reclaim/redeem the funds in an HTLC sent to/from us.
 	BlockEpochs *chainntnfs.BlockEpochEvent
 
+	// ChainEvents is an active subscription to the chain watcher for this
+	// channel to be notified of any on-chain activity related to this
+	// channel.
+	ChainEvents *ChainEventSubscription
+
 	// ForceCloseChan should force close the contract that this attendant
 	// is watching over. We'll use this when we decide that we need to go
 	// to chain. The returned summary contains all items needed to
@@ -164,10 +169,6 @@ type ChannelArbitrator struct {
 	// we're watching over will be sent.
 	signalUpdates chan *signalUpdateMsg
 
-	// uniCloseSignal is a channel that will be sent upon if we detect that
-	// the remote party closes the channel on-chain.
-	uniCloseSignal <-chan *lnwallet.UnilateralCloseSummary
-
 	// htlcUpdates is a channel that is sent upon with new updates from the
 	// active channel. Each time a new commitment state is accepted, the
 	// set of HTLC's on the new state should be sent across this channel.
@@ -202,7 +203,6 @@ func NewChannelArbitrator(cfg ChannelArbitratorConfig,
 	return &ChannelArbitrator{
 		log:              log,
 		signalUpdates:    make(chan *signalUpdateMsg),
-		uniCloseSignal:   make(<-chan *lnwallet.UnilateralCloseSummary),
 		htlcUpdates:      make(<-chan []channeldb.HTLC),
 		resolutionSignal: make(chan struct{}),
 		forceCloseReqs:   make(chan *forceCloseReq),
@@ -292,6 +292,8 @@ func (c *ChannelArbitrator) Stop() error {
 
 	log.Debugf("Stopping ChannelArbitrator(%v)", c.cfg.ChanPoint)
 
+	c.cfg.ChainEvents.Cancel()
+
 	for _, activeResolver := range c.activeResolvers {
 		activeResolver.Stop()
 	}
@@ -368,7 +370,8 @@ func (c *ChannelArbitrator) stateStep(bestHeight uint32, bestHash *chainhash.Has
 		// chain, we'll check to see if we need to make any on-chain
 		// claims on behalf of the channel contract that we're
 		// arbitrating for.
-		chainActions := c.checkChainActions(uint32(bestHeight), trigger)
+		chainActions := c.checkChainActions(uint32(bestHeight),
+			trigger)
 
 		// If there are no actions to be made, then we'll remain in the
 		// default state. If this isn't a self initiated event (we're
@@ -1320,7 +1323,6 @@ func (c *ChannelArbitrator) channelAttendant(bestHeight int32,
 
 			// First, we'll update our set of signals.
 			c.htlcUpdates = signalUpdate.newSignals.HtlcUpdates
-			c.uniCloseSignal = signalUpdate.newSignals.UniCloseSignal
 			c.cfg.ShortChanID = signalUpdate.newSignals.ShortChanID
 
 			// Now that the signals have been updated, we'll now
@@ -1347,7 +1349,7 @@ func (c *ChannelArbitrator) channelAttendant(bestHeight int32,
 		// The remote party has broadcast the commitment on-chain.
 		// We'll examine our state to determine if we need to act at
 		// all.
-		case uniClosure := <-c.uniCloseSignal:
+		case uniClosure := <-c.cfg.ChainEvents.UnilateralClosure:
 			if c.state != StateDefault {
 				continue
 			}