contractcourt/chain_watcher: mark fully closed in dispatchCoopClose

This commit makes the dispatchCooperativeClose method mark the channel
fully closed directly, without registering for confirmation
notifications first. We can do this as recent changes to the
contractcourt changed the definition of a closed channel in the database
to have had its closing tx confirmed, and we only dispatch the
cooperative close once the transaction has 1 confirmation.

We also rename the markChanClosed method to notifyChanClosed, to more
clearly indicate that the ChainArbitrator no longer has to mark the
channel fully closed in the database.

contractcourt/chain_watcher.go

@@ -78,10 +78,12 @@ type chainWatcherConfig struct {
 	// machine.
 	signer lnwallet.Signer
 
-	// markChanClosed is a method that will be called by the watcher if it
+	// notifyChanClosed is a method that will be called by the watcher when
-	// detects that a cooperative closure transaction has successfully been
+	// it has detected a close on-chain and performed all necessary
-	// confirmed.
+	// actions, like marking the channel closed in the database and
-	markChanClosed func() error
+	// notified all its subcribers. It lets the chain arbitrator know that
+	// the chain watcher chan be stopped.
+	notifyChanClosed func() error
 
 	// contractBreach is a method that will be called by the watcher if it
 	// detects that a contract breach transaction has been confirmed. Only
@@ -453,8 +455,9 @@ func (c *chainWatcher) dispatchCooperativeClose(commitSpend *chainntnfs.SpendDet
 	// ours.
 	localAmt := c.toSelfAmount(broadcastTx)
 
-	// Once this is known, we'll mark the state as pending close in the
+	// Once this is known, we'll mark the state as fully closed in the
-	// database.
+	// database. We can do this as a cooperatively closed channel has all
+	// its outputs resolved after only one confirmation.
 	closeSummary := &channeldb.ChannelCloseSummary{
 		ChanPoint:      c.cfg.chanState.FundingOutpoint,
 		ChainHash:      c.cfg.chanState.ChainHash,
@@ -465,7 +468,7 @@ func (c *chainWatcher) dispatchCooperativeClose(commitSpend *chainntnfs.SpendDet
 		SettledBalance: localAmt,
 		CloseType:      channeldb.CooperativeClose,
 		ShortChanID:    c.cfg.chanState.ShortChanID(),
-		IsPending:      true,
+		IsPending:      false,
 	}
 	err := c.cfg.chanState.CloseChannel(closeSummary)
 	if err != nil && err != channeldb.ErrNoActiveChannels &&
@@ -473,45 +476,10 @@ func (c *chainWatcher) dispatchCooperativeClose(commitSpend *chainntnfs.SpendDet
 		return fmt.Errorf("unable to close chan state: %v", err)
 	}
 
-	// Finally, we'll launch a goroutine to mark the channel as fully
-	// closed once the transaction confirmed.
-	go func() {
-		confNtfn, err := c.cfg.notifier.RegisterConfirmationsNtfn(
-			commitSpend.SpenderTxHash, 1,
-			uint32(commitSpend.SpendingHeight),
-		)
-		if err != nil {
-			log.Errorf("unable to register for conf: %v", err)
-			return
-		}
-
-		log.Infof("closeObserver: waiting for txid=%v to close "+
-			"ChannelPoint(%v) on chain", commitSpend.SpenderTxHash,
-			c.cfg.chanState.FundingOutpoint)
-
-		select {
-		case confInfo, ok := <-confNtfn.Confirmed:
-			if !ok {
-				log.Errorf("notifier exiting")
-				return
-			}
-
 	log.Infof("closeObserver: ChannelPoint(%v) is fully "+
 		"closed, at height: %v",
 		c.cfg.chanState.FundingOutpoint,
-				confInfo.BlockHeight)
+		commitSpend.SpendingHeight)
-
-			err := c.cfg.markChanClosed()
-			if err != nil {
-				log.Errorf("unable to mark chan fully "+
-					"closed: %v", err)
-				return
-			}
-
-		case <-c.quit:
-			return
-		}
-	}()
 
 	c.Lock()
 	for _, sub := range c.clientSubscriptions {
@@ -524,6 +492,14 @@ func (c *chainWatcher) dispatchCooperativeClose(commitSpend *chainntnfs.SpendDet
 	}
 	c.Unlock()
 
+	// Now notify the ChainArbitrator that the watcher's job is done, such
+	// that it can shut it down and clean up.
+	if err := c.cfg.notifyChanClosed(); err != nil {
+		log.Errorf("unable to notify channel closed for "+
+			"ChannelPoint(%v): %v",
+			c.cfg.chanState.FundingOutpoint, err)
+	}
+
 	return nil
 
 }