Boostrap empty RT and Optimize allocs when we discover new peers (#631)

* Bootstrap when RT is empty and optimize allocations.

Co-authored-by: Steven Allen <[email protected]>

Author: aarshkshah1992

dht.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"math"
+	"math/rand"
 	"sync"
 	"time"
 
@@ -86,7 +87,8 @@ type IpfsDHT struct {
 
 	// DHT protocols we query with. We'll only add peers to our routing
 	// table if they speak these protocols.
-	protocols []protocol.ID
+	protocols     []protocol.ID
+	protocolsStrs []string
 
 	// DHT protocols we can respond to.
 	serverProtocols []protocol.ID
@@ -108,6 +110,11 @@ type IpfsDHT struct {
 	triggerRtRefresh      chan chan<- error
 	triggerSelfLookup     chan chan<- error
 
+	// A set of bootstrap peers to fallback on if all other attempts to fix
+	// the routing table fail (or, e.g., this is the first time this node is
+	// connecting to the network).
+	bootstrapPeers []peer.AddrInfo
+
 	maxRecordAge time.Duration
 
 	// Allows disabling dht subsystems. These should _only_ be set on
@@ -254,6 +261,7 @@ func makeDHT(ctx context.Context, h host.Host, cfg config) (*IpfsDHT, error) {
 		strmap:                 make(map[peer.ID]*messageSender),
 		birth:                  time.Now(),
 		protocols:              protocols,
+		protocolsStrs:          protocol.ConvertToStrings(protocols),
 		serverProtocols:        serverProtocols,
 		bucketSize:             cfg.bucketSize,
 		alpha:                  cfg.concurrency,
@@ -262,7 +270,7 @@ func makeDHT(ctx context.Context, h host.Host, cfg config) (*IpfsDHT, error) {
 		triggerSelfLookup:      make(chan chan<- error),
 		queryPeerFilter:        cfg.queryPeerFilter,
 		routingTablePeerFilter: cfg.routingTable.peerFilter,
-		fixLowPeersChan:        make(chan struct{}),
+		fixLowPeersChan:        make(chan struct{}, 1),
 	}
 
 	// construct routing table
@@ -271,6 +279,7 @@ func makeDHT(ctx context.Context, h host.Host, cfg config) (*IpfsDHT, error) {
 		return nil, fmt.Errorf("failed to construct routing table,err=%s", err)
 	}
 	dht.routingTable = rt
+	dht.bootstrapPeers = cfg.bootstrapPeers
 
 	// create a DHT proc with the given context
 	dht.proc = goprocessctx.WithContext(ctx)
@@ -323,22 +332,70 @@ func (dht *IpfsDHT) Mode() ModeOpt {
 	return dht.auto
 }
 
-// fixLowPeers tries to get more peers into the routing table if we're below the threshold
+// fixLowPeersRoutine tries to get more peers into the routing table if we're below the threshold
 func (dht *IpfsDHT) fixLowPeersRoutine(proc goprocess.Process) {
+	timer := time.NewTimer(periodicBootstrapInterval)
+	defer timer.Stop()
+
 	for {
 		select {
 		case <-dht.fixLowPeersChan:
+		case <-timer.C:
 		case <-proc.Closing():
 			return
 		}
+
 		if dht.routingTable.Size() > minRTRefreshThreshold {
 			continue
 		}
 
+		// we try to add all peers we are connected to to the Routing Table
+		// in case they aren't already there.
 		for _, p := range dht.host.Network().Peers() {
 			dht.peerFound(dht.Context(), p, false)
 		}
 
+		// TODO Active Bootstrapping
+		// We should first use non-bootstrap peers we knew of from previous
+		// snapshots of the Routing Table before we connect to the bootstrappers.
+		// See https://github.com/libp2p/go-libp2p-kad-dht/issues/387.
+		if dht.routingTable.Size() == 0 {
+			if len(dht.bootstrapPeers) == 0 {
+				// No point in continuing, we have no peers!
+				continue
+			}
+
+			found := 0
+			for _, i := range rand.Perm(len(dht.bootstrapPeers)) {
+				ai := dht.bootstrapPeers[i]
+				err := dht.Host().Connect(dht.Context(), ai)
+				if err == nil {
+					found++
+				} else {
+					logger.Warnw("failed to bootstrap", "peer", ai.ID, "error", err)
+				}
+
+				// Wait for two bootstrap peers, or try them all.
+				//
+				// Why two? In theory, one should be enough
+				// normally. However, if the network were to
+				// restart and everyone connected to just one
+				// bootstrapper, we'll end up with a mostly
+				// partitioned network.
+				//
+				// So we always bootstrap with two random peers.
+				if found == maxNBoostrappers {
+					break
+				}
+			}
+		}
+
+		// if we still don't have peers in our routing table(probably because Identify hasn't completed),
+		// there is no point in triggering a Refresh.
+		if dht.routingTable.Size() == 0 {
+			continue
+		}
+
 		if dht.autoRefresh {
 			select {
 			case dht.triggerRtRefresh <- nil:
@@ -504,9 +561,6 @@ func (dht *IpfsDHT) peerStoppedDHT(ctx context.Context, p peer.ID) {
 	// A peer that does not support the DHT protocol is dead for us.
 	// There's no point in talking to anymore till it starts supporting the DHT protocol again.
 	dht.routingTable.RemovePeer(p)
-
-	// since we lost a peer from the RT, we should do this here
-	dht.fixRTIfNeeded()
 }
 
 func (dht *IpfsDHT) fixRTIfNeeded() {

dht_bootstrap.go

@@ -22,6 +22,10 @@ var minRTRefreshThreshold = 10
 
 // timeout for pinging one peer
 const peerPingTimeout = 10 * time.Second
+const (
+	periodicBootstrapInterval = 2 * time.Minute
+	maxNBoostrappers          = 2
+)
 
 func init() {
 	for _, s := range []string{

dht_options.go

@@ -13,6 +13,7 @@ import (
 	"github.com/libp2p/go-libp2p-core/protocol"
 	"github.com/libp2p/go-libp2p-kad-dht/providers"
 	record "github.com/libp2p/go-libp2p-record"
+	ma "github.com/multiformats/go-multiaddr"
 )
 
 // ModeOpt describes what mode the dht should operate in
@@ -60,6 +61,7 @@ type config struct {
 
 	// set to true if we're operating in v1 dht compatible mode
 	v1CompatibleMode bool
+	bootstrapPeers   []peer.AddrInfo
 }
 
 func emptyQueryFilter(_ *IpfsDHT, ai peer.AddrInfo) bool  { return true }
@@ -393,3 +395,16 @@ func V1CompatibleMode(enable bool) Option {
 		return nil
 	}
 }
+
+// BootstrapPeers configures the bootstrapping nodes that we will connect to to seed
+// and refresh our Routing Table if it becomes empty.
+func BootstrapPeers(addrs ...ma.Multiaddr) Option {
+	return func(c *config) error {
+		bootstrappers, err := peer.AddrInfosFromP2pAddrs(addrs...)
+		if err != nil {
+			return fmt.Errorf("failed to parse bootstrap peer addresses: %w", err)
+		}
+		c.bootstrapPeers = bootstrappers
+		return nil
+	}
+}

dht_test.go

@@ -1966,3 +1966,107 @@ func TestRoutingFilter(t *testing.T) {
 	case <-time.After(time.Millisecond * 200):
 	}
 }
+
+func TestBootStrapWhenRTIsEmpty(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	// create three boostrap peers each of which is connected to 1 other peer.
+	nBootStraps := 3
+	bootstrappers := setupDHTS(t, ctx, nBootStraps)
+	defer func() {
+		for i := 0; i < nBootStraps; i++ {
+			bootstrappers[i].Close()
+			defer bootstrappers[i].host.Close()
+		}
+	}()
+
+	bootstrapcons := setupDHTS(t, ctx, nBootStraps)
+	defer func() {
+		for i := 0; i < nBootStraps; i++ {
+			bootstrapcons[i].Close()
+			defer bootstrapcons[i].host.Close()
+		}
+	}()
+	for i := 0; i < nBootStraps; i++ {
+		connect(t, ctx, bootstrappers[i], bootstrapcons[i])
+	}
+
+	// convert the bootstrap addresses to a p2p address
+	bootstrapAddrs := make([]ma.Multiaddr, nBootStraps)
+	for i := 0; i < nBootStraps; i++ {
+		b, err := peer.AddrInfoToP2pAddrs(&peer.AddrInfo{ID: bootstrappers[i].self,
+			Addrs: bootstrappers[i].host.Addrs()})
+		require.NoError(t, err)
+		bootstrapAddrs[i] = b[0]
+	}
+
+	//----------------
+	// We will initialize a DHT with 1 bootstrapper, connect it to another DHT,
+	// then remove the latter from the Routing Table
+	// This should add the bootstrap peer and the peer that the bootstrap peer is conencted to
+	// to it's Routing Table.
+	// AutoRefresh needs to be enabled for this.
+	dht1, err := New(
+		ctx,
+		bhost.New(swarmt.GenSwarm(t, ctx, swarmt.OptDisableReuseport)),
+		testPrefix,
+		NamespacedValidator("v", blankValidator{}),
+		Mode(ModeServer),
+		BootstrapPeers(bootstrapAddrs[0]),
+	)
+	require.NoError(t, err)
+	dht2 := setupDHT(ctx, t, false)
+	defer func() {
+		dht1.host.Close()
+		dht2.host.Close()
+		dht1.Close()
+		dht2.Close()
+	}()
+	connect(t, ctx, dht1, dht2)
+	require.NoError(t, dht2.Close())
+	require.NoError(t, dht2.host.Close())
+	require.NoError(t, dht1.host.Network().ClosePeer(dht2.self))
+	dht1.routingTable.RemovePeer(dht2.self)
+	require.NotContains(t, dht2.self, dht1.routingTable.ListPeers())
+
+	require.Eventually(t, func() bool {
+		return dht1.routingTable.Size() == 2 && dht1.routingTable.Find(bootstrappers[0].self) != "" &&
+			dht1.routingTable.Find(bootstrapcons[0].self) != ""
+	}, 5*time.Second, 500*time.Millisecond)
+
+	//----------------
+	// We will initialize a DHT with 2 bootstrappers, connect it to another DHT,
+	// then remove the DHT handler from the other DHT which should make the first DHT's
+	// routing table empty.
+	// This should add the bootstrap peers and the peer thats the bootstrap peers are connected to
+	// to it's Routing Table.
+	// AutoRefresh needs to be enabled for this.
+	dht1, err = New(
+		ctx,
+		bhost.New(swarmt.GenSwarm(t, ctx, swarmt.OptDisableReuseport)),
+		testPrefix,
+		NamespacedValidator("v", blankValidator{}),
+		Mode(ModeServer),
+		BootstrapPeers(bootstrapAddrs[1], bootstrapAddrs[2]),
+	)
+	require.NoError(t, err)
+
+	dht2 = setupDHT(ctx, t, false)
+	connect(t, ctx, dht1, dht2)
+	defer func() {
+		dht1.host.Close()
+		dht2.host.Close()
+		dht1.Close()
+		dht2.Close()
+	}()
+	connect(t, ctx, dht1, dht2)
+	require.NoError(t, dht2.setMode(modeClient))
+
+	require.Eventually(t, func() bool {
+		rt := dht1.routingTable
+
+		return rt.Size() == 4 && rt.Find(bootstrappers[1].self) != "" &&
+			rt.Find(bootstrappers[2].self) != "" && rt.Find(bootstrapcons[1].self) != "" && rt.Find(bootstrapcons[2].self) != ""
+	}, 5*time.Second, 500*time.Millisecond)
+}

go.mod

@@ -17,9 +17,9 @@ require (
 	github.com/jbenet/goprocess v0.1.4
 	github.com/libp2p/go-eventbus v0.1.0
 	github.com/libp2p/go-libp2p v0.8.2
-	github.com/libp2p/go-libp2p-core v0.5.3
-	github.com/libp2p/go-libp2p-kbucket v0.4.1
-	github.com/libp2p/go-libp2p-peerstore v0.2.3
+	github.com/libp2p/go-libp2p-core v0.5.4
+	github.com/libp2p/go-libp2p-kbucket v0.4.2
+	github.com/libp2p/go-libp2p-peerstore v0.2.4
 	github.com/libp2p/go-libp2p-record v0.1.2
 	github.com/libp2p/go-libp2p-routing-helpers v0.2.3
 	github.com/libp2p/go-libp2p-swarm v0.2.3
@@ -28,7 +28,7 @@ require (
 	github.com/libp2p/go-netroute v0.1.2
 	github.com/multiformats/go-base32 v0.0.3
 	github.com/multiformats/go-multiaddr v0.2.1
-	github.com/multiformats/go-multiaddr-net v0.1.4
+	github.com/multiformats/go-multiaddr-net v0.1.5
 	github.com/multiformats/go-multihash v0.0.13
 	github.com/multiformats/go-multistream v0.1.1
 	github.com/stretchr/testify v1.5.1