wtclient: add TerminateSession method

watchtower/wtclient/client.go

@@ -148,6 +148,19 @@ type deactivateTowerMsg struct {
 	errChan chan error
 }
 
+// terminateSessMsg is an internal message we'll use within the TowerClient to
+// signal that a session should be terminated.
+type terminateSessMsg struct {
+	// id is the session identifier.
+	id wtdb.SessionID
+
+	// errChan is the channel through which we'll send a response back to
+	// the caller when handling their request.
+	//
+	// NOTE: This channel must be buffered.
+	errChan chan error
+}
+
 // clientCfg holds the configuration values required by a client.
 type clientCfg struct {
 	*Config
@@ -184,6 +197,7 @@ type client struct {
 	newTowers         chan *newTowerMsg
 	staleTowers       chan *staleTowerMsg
 	deactivateTowers  chan *deactivateTowerMsg
+	terminateSessions chan *terminateSessMsg
 
 	wg   sync.WaitGroup
 	quit chan struct{}
@@ -218,6 +232,7 @@ func newClient(cfg *clientCfg) (*client, error) {
 		newTowers:         make(chan *newTowerMsg),
 		staleTowers:       make(chan *staleTowerMsg),
 		deactivateTowers:  make(chan *deactivateTowerMsg),
+		terminateSessions: make(chan *terminateSessMsg),
 		quit:              make(chan struct{}),
 	}
 
@@ -718,6 +733,10 @@ func (c *client) backupDispatcher() {
 			case msg := <-c.deactivateTowers:
 				msg.errChan <- c.handleDeactivateTower(msg)
 
+			// A request has come through to terminate a session.
+			case msg := <-c.terminateSessions:
+				msg.errChan <- c.handleTerminateSession(msg)
+
 			case <-c.quit:
 				return
 			}
@@ -807,6 +826,10 @@ func (c *client) backupDispatcher() {
 			case msg := <-c.deactivateTowers:
 				msg.errChan <- c.handleDeactivateTower(msg)
 
+			// A request has come through to terminate a session.
+			case msg := <-c.terminateSessions:
+				msg.errChan <- c.handleTerminateSession(msg)
+
 			case <-c.quit:
 				return
 			}
@@ -1074,6 +1097,53 @@ func (c *client) initActiveQueue(s *ClientSession,
 	return sq
 }
 
+// terminateSession sets the given session's status to CSessionTerminal meaning
+// that it will not be used again.
+func (c *client) terminateSession(id wtdb.SessionID) error {
+	errChan := make(chan error, 1)
+
+	select {
+	case c.terminateSessions <- &terminateSessMsg{
+		id:      id,
+		errChan: errChan,
+	}:
+	case <-c.pipeline.quit:
+		return ErrClientExiting
+	}
+
+	select {
+	case err := <-errChan:
+		return err
+	case <-c.pipeline.quit:
+		return ErrClientExiting
+	}
+}
+
+// handleTerminateSession handles a request to terminate a session. It will
+// first shut down the session if it is part of the active session set, then
+// it will ensure that the active session queue is set reset if it is using the
+// session in question. Finally, the session's status in the DB will be updated.
+func (c *client) handleTerminateSession(msg *terminateSessMsg) error {
+	id := msg.id
+
+	delete(c.candidateSessions, id)
+
+	err := c.activeSessions.StopAndRemove(id, true)
+	if err != nil {
+		return fmt.Errorf("could not stop session %s: %w", id, err)
+	}
+
+	// If our active session queue corresponds to the session being
+	// terminated, then we'll proceed to negotiate a new one.
+	if c.sessionQueue != nil {
+		if bytes.Equal(c.sessionQueue.ID()[:], id[:]) {
+			c.sessionQueue = nil
+		}
+	}
+
+	return nil
+}
+
 // deactivateTower sends a tower deactivation request to the backupDispatcher
 // where it will be handled synchronously. The request should result in all the
 // sessions that we have with the given tower being shutdown and removed from

watchtower/wtclient/client_test.go

@@ -1034,15 +1034,19 @@ func (s *serverHarness) waitForUpdates(hints []blob.BreachHint,
 	// Closure to assert the server's matches are consistent with the hint
 	// set.
 	serverHasHints := func(matches []wtdb.Match) bool {
-		if len(hintSet) != len(matches) {
+		// De-dup the server matches since it might very well have
+		// multiple matches for a hint if that update was backed up on
+		// more than one session.
+		matchHints := make(map[blob.BreachHint]struct{})
+		for _, match := range matches {
+			matchHints[match.Hint] = struct{}{}
+		}
+
+		if len(hintSet) != len(matchHints) {
 			return false
 		}
 
-		for _, match := range matches {
+		require.EqualValues(s.t, hintSet, matchHints)
-			_, ok := hintSet[match.Hint]
-			require.Truef(s.t, ok, "match %v in db is not in "+
-				"hint set", match.Hint)
-		}
 
 		return true
 	}
@@ -2770,6 +2774,123 @@ var clientTests = []clientTest{
 			h.server.waitForUpdates(hints[numUpdates-1:], waitTime)
 		},
 	},
+	{
+		name: "terminate session",
+		cfg: harnessCfg{
+			localBalance:  localBalance,
+			remoteBalance: remoteBalance,
+			policy: wtpolicy.Policy{
+				TxPolicy:   defaultTxPolicy,
+				MaxUpdates: 5,
+			},
+		},
+		fn: func(h *testHarness) {
+			const (
+				numUpdates = 10
+				chanIDInt  = 0
+			)
+
+			// Advance the channel with a few updates.
+			hints := h.advanceChannelN(chanIDInt, numUpdates)
+
+			// Backup one of these updates and wait for it to
+			// arrive at the server.
+			h.backupStates(chanIDInt, 0, 1, nil)
+			h.server.waitForUpdates(hints[:1], waitTime)
+
+			// Now, restart the server in a state where it will not
+			// ack updates. This will allow us to wait for an update
+			// to be un-acked and persisted.
+			h.server.restart(func(cfg *wtserver.Config) {
+				cfg.NoAckUpdates = true
+			})
+
+			// Backup another update. These should remain in the
+			// client as un-acked.
+			h.backupStates(chanIDInt, 1, 2, nil)
+
+			// Wait for the update to be persisted.
+			fetchUnacked := h.clientDB.FetchSessionCommittedUpdates
+			var sessID wtdb.SessionID
+			err := wait.Predicate(func() bool {
+				sessions, err := h.clientDB.ListClientSessions(
+					nil,
+				)
+				require.NoError(h.t, err)
+
+				var updates []wtdb.CommittedUpdate
+				for id := range sessions {
+					sessID = id
+					updates, err = fetchUnacked(&id)
+					require.NoError(h.t, err)
+
+					return len(updates) == 1
+				}
+
+				return false
+			}, waitTime)
+			require.NoError(h.t, err)
+
+			// Now try to terminate the session by directly calling
+			// the DB terminate method. This is expected to fail
+			// since the session still has un-acked updates.
+			err = h.clientDB.TerminateSession(sessID)
+			require.ErrorIs(
+				h.t, err, wtdb.ErrSessionHasUnackedUpdates,
+			)
+
+			// If we try to terminate the session through the client
+			// interface though, it should succeed since the client
+			// will handle the un-acked updates of the session.
+			err = h.clientMgr.TerminateSession(sessID)
+			require.NoError(h.t, err)
+
+			// Fetch the session from the DB and assert that it is
+			// in the terminal state and that it is not exhausted.
+			sess, err := h.clientDB.GetClientSession(sessID)
+			require.NoError(h.t, err)
+
+			require.Equal(h.t, wtdb.CSessionTerminal, sess.Status)
+			require.NotEqual(
+				h.t, sess.Policy.MaxUpdates, sess.SeqNum,
+			)
+
+			// Restart the server and allow it to ack updates again.
+			h.server.restart(func(cfg *wtserver.Config) {
+				cfg.NoAckUpdates = false
+			})
+
+			// Wait for the update from before to appear on the
+			// server. The server will actually have this back-up
+			// stored twice now since it would have stored it for
+			// the first session even though it did not send an ACK
+			// for it.
+			h.server.waitForUpdates(hints[1:2], waitTime)
+
+			// Now we want to assert that this update was definitely
+			// not sent on the terminated session but was instead
+			// sent in a new session.
+			var (
+				updateCounts = make(map[wtdb.SessionID]uint16)
+				totalUpdates uint16
+			)
+			sessions, err := h.clientDB.ListClientSessions(nil,
+				wtdb.WithPerNumAckedUpdates(
+					func(s *wtdb.ClientSession,
+						_ lnwire.ChannelID,
+						num uint16) {
+
+						updateCounts[s.ID] += num
+						totalUpdates += num
+					},
+				),
+			)
+			require.NoError(h.t, err)
+			require.Len(h.t, sessions, 2)
+			require.EqualValues(h.t, 1, updateCounts[sessID])
+			require.EqualValues(h.t, 2, totalUpdates)
+		},
+	},
 }
 
 // TestClient executes the client test suite, asserting the ability to backup

watchtower/wtclient/manager.go

@@ -43,6 +43,10 @@ type ClientManager interface {
 	// be used while the tower is inactive.
 	DeactivateTower(pubKey *btcec.PublicKey) error
 
+	// TerminateSession sets the given session's status to CSessionTerminal
+	// meaning that it will not be used again.
+	TerminateSession(id wtdb.SessionID) error
+
 	// Stats returns the in-memory statistics of the client since startup.
 	Stats() ClientStats
 
@@ -436,6 +440,23 @@ func (m *Manager) RemoveTower(key *btcec.PublicKey, addr net.Addr) error {
 	return nil
 }
 
+// TerminateSession sets the given session's status to CSessionTerminal meaning
+// that it will not be used again.
+func (m *Manager) TerminateSession(id wtdb.SessionID) error {
+	m.clientsMu.Lock()
+	defer m.clientsMu.Unlock()
+
+	for _, client := range m.clients {
+		err := client.terminateSession(id)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Finally, mark the session as terminated in the DB.
+	return m.cfg.DB.TerminateSession(id)
+}
+
 // DeactivateTower sets the given tower's status to inactive so that it is not
 // considered for session negotiation. Its sessions will also not be used while
 // the tower is inactive.