Peer backup

peer/brontide.go

@@ -76,6 +76,8 @@ const (
 
 	// ErrorBufferSize is the number of historic peer errors that we store.
 	ErrorBufferSize = 10
+
+	backupUpdateInterval = 1 * time.Second
 )
 
 var (
@@ -518,6 +520,7 @@ type Brontide struct {
 	// backupData is an in-memory store for data that we store for our
 	// peers.
 	backupData lnwire.PeerStorageBlob
+	bMtx       *sync.Cond
 }
 
 // A compile-time check to ensure that Brontide satisfies the lnpeer.Peer interface.
@@ -549,6 +552,7 @@ func NewBrontide(cfg Config) *Brontide {
 		startReady:         make(chan struct{}),
 		quit:               make(chan struct{}),
 		log:                build.NewPrefixLog(logPrefix, peerLog),
+		bMtx:               sync.NewCond(&sync.Mutex{}),
 	}
 
 	var (
@@ -752,10 +756,14 @@ func (p *Brontide) Start() error {
 		return fmt.Errorf("could not start ping manager %w", err)
 	}
 
-	p.wg.Add(4)
+	p.wg.Add(5)
 	go p.queueHandler()
 	go p.writeHandler()
 	go p.channelManager()
+
+	// Initialize peerStorageWriter before readHandler to ensure readiness
+	// for storing `PeerStorage` messages upon receipt.
+	go p.peerStorageWriter()
 	go p.readHandler()
 
 	// Signal to any external processes that the peer is now active.
@@ -777,6 +785,75 @@ func (p *Brontide) Start() error {
 	return nil
 }
 
+// peerStorageWriter coordinates persisting peer's backup data by delaying its
+// storage from its time of receipt to its time of persistence by the
+// duration specified in the `backupUpdateInterval`.
+func (p *Brontide) peerStorageWriter() {
+	defer p.wg.Done()
+
+	var data []byte
+
+Loop:
+	p.bMtx.L.Lock()
+	for {
+		p.bMtx.Wait()
+
+		// Store the data in a different variable as we are about to
+		// exit lock.
+		data = p.backupData
+		p.bMtx.L.Unlock()
+
+		// Check if we are to exit, now that we are awake.
+		select {
+		case <-p.quit:
+			if data == nil {
+				return
+			}
+
+			// Store the data immediately and exit.
+			err := p.cfg.PeerDataStore.Store(data)
+			if err != nil {
+				peerLog.Warnf("Failed to store peer "+
+					"backup data: %v", err)
+			}
+
+			return
+
+		default:
+		}
+
+		break
+	}
+
+	t := time.NewTicker(backupUpdateInterval)
+
+	select {
+	case <-t.C:
+		// Store the data.
+		err := p.cfg.PeerDataStore.Store(data)
+		if err != nil {
+			peerLog.Criticalf("Failed to store peer "+
+				"backup data: %v", err)
+		}
+
+		goto Loop
+
+	case <-p.quit:
+		if data == nil {
+			return
+		}
+
+		// Store the data immediately and exit.
+		err := p.cfg.PeerDataStore.Store(data)
+		if err != nil {
+			peerLog.Warnf("Failed to store peer backup "+
+				"data: %v", err)
+		}
+
+		return
+	}
+}
+
 // initGossipSync initializes either a gossip syncer or an initial routing
 // dump, depending on the negotiated synchronization method.
 func (p *Brontide) initGossipSync() {
@@ -1286,6 +1363,10 @@ func (p *Brontide) Disconnect(reason error) {
 
 	close(p.quit)
 
+	// Signal the peerStorageWriter to stop waiting and pick up the close
+	// signal.
+	p.bMtx.Signal()
+
 	if err := p.pingManager.Stop(); err != nil {
 		p.log.Errorf("couldn't stop pingManager during disconnect: %v",
 			err)
@@ -4210,7 +4291,10 @@ func (p *Brontide) handlePeerStorageMessage(msg *lnwire.PeerStorage) error {
 
 	p.log.Debugf("handling peerbackup for peer(%s)", p)
 
+	p.bMtx.L.Lock()
 	p.backupData = msg.Blob
+	p.bMtx.Signal()
+	p.bMtx.L.Unlock()
 
 	return nil
 }

peer/brontide_test.go

@@ -1569,3 +1569,89 @@ func TestHandlePeerStorage(t *testing.T) {
 		})
 	}
 }
+
+// TestPeerStorageWriter tests the peerStorageWriter function.
+func TestPeerStorageWriter(t *testing.T) {
+	harness := createTestPeer(t)
+	peer := harness.peer
+
+	// Start the function in a goroutine to test its functionality in
+	// another thread. A successful test means the function started and
+	// performed as expected.
+	peer.wg.Add(1)
+	go peer.peerStorageWriter()
+
+	// Update the backupData every quarter of the backupUpdateInterval.
+	// We do this to test that only the most recent update within this
+	// interval is persisted. This also tests that indeed, the storage is
+	// delayed.
+	interval := backupUpdateInterval / 4
+
+	// We would update the backupData eight times at every quarter of the
+	// backupUpdateInterval. That means this process would go on for
+	// 2 times the backupUpdateInterval duration.
+	for i := 0; i < 8; i++ {
+		ti := time.NewTicker(interval)
+		select {
+		case <-ti.C:
+			peer.bMtx.L.Lock()
+			peer.backupData = []byte{byte(i)}
+			peer.bMtx.Signal()
+			peer.bMtx.L.Unlock()
+
+		case <-time.After(1 * time.Second):
+			t.Fatalf("did not receive ticker as expected.")
+		}
+	}
+
+	// We expect to persist initial backup data at index 0. After one full
+	// backupUpdateInterval, the next data to be persisted is at index 4.
+	// Between data at index 4 and the final data at index 7, only 3/4 of
+	// the backupUpdateInterval elapses. The remaining interval is completed
+	// with this sleep command, so that the data at index 4 would be
+	// persisted.
+	time.Sleep(backupUpdateInterval / 4)
+
+	retrievedData, err := peer.cfg.PeerDataStore.Retrieve()
+	require.NoError(t, err)
+
+	// We expect one data persisted within a backupUpdateInterval.
+	// Since we sent updates within a duration of two times the
+	// backupUpdateInterval, we expect to have persisted two updates
+	// only.
+	require.Len(t, retrievedData, 2)
+
+	// Convert the data to its corresponding integer values.
+	convToIntData := func(retrievedData []byte) []int {
+		return fn.Map(func(b byte) int {
+			return int(b)
+		}, retrievedData)
+	}
+
+	// The backup data was updated eight times, each annotated with its
+	// index. Due to the delay, we expect only the data from the zeroth and
+	// fourth updates to be persisted in that order.
+	require.Equal(t, []int{0, 4}, convToIntData(retrievedData))
+
+	// Test that we store remaining data on quit.
+	close(peer.quit)
+	peer.bMtx.Signal()
+
+	// The signal for data at index 7 wasn't picked up because it
+	// was sent during the storage delay for data at index 4.
+	// After sending another signal, we expect the
+	// `peerStorageWriter` to now pick it up, then bypass the
+	// storage delay and persist it immediately as we have now
+	// closed the peer's quit channel as well.
+	//
+	// Wait a bit to allow for storing before we retrieve.
+	time.Sleep(time.Second / 2)
+	retrievedData, err = peer.cfg.PeerDataStore.Retrieve()
+	require.NoError(t, err)
+
+	require.Len(t, retrievedData, 3)
+	require.Equal(t, []int{0, 4, 7}, convToIntData(retrievedData))
+
+	// Wait for goroutine to exit(good manners).
+	peer.wg.Wait()
+}

peer/test_utils.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"math/rand"
 	"net"
+	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -538,6 +539,46 @@ func (m *mockMessageConn) Close() error {
 	return nil
 }
 
+type mockPeerDataStore struct {
+	data [][]byte
+	mtx  sync.RWMutex
+}
+
+func newMockDataStore() *mockPeerDataStore {
+	return &mockPeerDataStore{}
+}
+
+// Store persists the backup data given to us by peers.
+func (d *mockPeerDataStore) Store(data []byte) error {
+	d.mtx.Lock()
+	defer d.mtx.Unlock()
+
+	d.data = append(d.data, data)
+
+	return nil
+}
+
+// Delete deletes the peer with PeerPub public key from the storage layer.
+func (d *mockPeerDataStore) Delete() error {
+	d.mtx.Lock()
+	defer d.mtx.Unlock()
+
+	d.data = nil
+
+	return nil
+}
+
+// Retrieve obtains data for peer with peerPub public key from the storage
+// layer.
+func (d *mockPeerDataStore) Retrieve() (
+	[]byte, error) {
+
+	d.mtx.RLock()
+	defer d.mtx.RUnlock()
+
+	return fn.Flatten(d.data), nil
+}
+
 // createTestPeer creates a new peer for testing and returns a context struct
 // containing necessary handles and mock objects for conducting tests on peer
 // functionalities.
@@ -708,7 +749,8 @@ func createTestPeer(t *testing.T) *peerTestCtx {
 
 			return nil
 		},
-		PongBuf: make([]byte, lnwire.MaxPongBytes),
+		PongBuf:       make([]byte, lnwire.MaxPongBytes),
+		PeerDataStore: newMockDataStore(),
 	}
 
 	alicePeer := NewBrontide(*cfg)