Persisting/seeding a routing table

dht.go

@@ -8,13 +8,14 @@ import (
 	"sync"
 	"time"
 
+	"github.com/jbenet/goprocess/periodic"
 	"github.com/libp2p/go-libp2p-core/host"
 	"github.com/libp2p/go-libp2p-core/network"
 	"github.com/libp2p/go-libp2p-core/peer"
 	"github.com/libp2p/go-libp2p-core/peerstore"
 	"github.com/libp2p/go-libp2p-core/protocol"
 	"github.com/libp2p/go-libp2p-core/routing"
-
+	"github.com/libp2p/go-libp2p-kad-dht/persist"
 	"go.opencensus.io/tag"
 	"golang.org/x/xerrors"
 
@@ -33,10 +34,15 @@ import (
 	record "github.com/libp2p/go-libp2p-record"
 	recpb "github.com/libp2p/go-libp2p-record/pb"
 	"github.com/multiformats/go-base32"
+	pkgerr "github.com/pkg/errors"
 )
 
 var logger = logging.Logger("dht")
 
+// NumBootstrapQueries defines the number of random dht queries to do to
+// collect members of the routing table.
+const NumBootstrapQueries = 5
+
 const BaseConnMgrScore = 5
 
 // IpfsDHT is an implementation of Kademlia with S/Kademlia modifications.
@@ -72,8 +78,17 @@ type IpfsDHT struct {
 	autoRefresh           bool
 	rtRefreshQueryTimeout time.Duration
 	rtRefreshPeriod       time.Duration
+	bootstrapCfg          opts.BootstrapConfig
 	triggerRtRefresh      chan chan<- error
 
+	triggerBootstrap chan struct{}
+
+	seedsProposer         persist.SeedsProposer
+	seederRTSizeTarget    int
+	seederDialTimeout     time.Duration
+	seederConcurrentDials int
+	totalSeederTimeout    time.Duration
+
 	maxRecordAge time.Duration
 
 	// Allows disabling dht subsystems. These should _only_ be set on
@@ -94,31 +109,61 @@ var (
 
 // New creates a new DHT with the specified host and options.
 func New(ctx context.Context, h host.Host, options ...opts.Option) (*IpfsDHT, error) {
-	var cfg opts.Options
+	cfg := &opts.Options{}
 	cfg.BucketSize = KValue
 	if err := cfg.Apply(append([]opts.Option{opts.Defaults}, options...)...); err != nil {
 		return nil, err
 	}
-	dht := makeDHT(ctx, h, cfg.Datastore, cfg.Protocols, cfg.BucketSize)
-	dht.autoRefresh = cfg.RoutingTable.AutoRefresh
-	dht.rtRefreshPeriod = cfg.RoutingTable.RefreshPeriod
-	dht.rtRefreshQueryTimeout = cfg.RoutingTable.RefreshQueryTimeout
 
-	dht.maxRecordAge = cfg.MaxRecordAge
-	dht.enableProviders = cfg.EnableProviders
-	dht.enableValues = cfg.EnableValues
+	// set seedsProposer, snapshotter & fallback peers if not set
+	if cfg.Persistence.SeedsProposer == nil {
+		cfg.Persistence.SeedsProposer = persist.NewRandomSeedsProposer()
+	}
+	snapshotter := cfg.Persistence.Snapshotter
+	if snapshotter == nil {
+		s, err := persist.NewDatastoreSnapshotter(cfg.Datastore, persist.DefaultSnapshotNS)
+		// should never happen
+		if err != nil {
+			logger.Errorf("failed to initialize the default datastore backed snapshotter, err: %s", err)
+			return nil, pkgerr.WithMessage(err, "failed to initialize the default datastore backed snapshotter")
+		}
+		snapshotter = s
+	}
 
-	// register for network notifs.
-	dht.host.Network().Notify((*netNotifiee)(dht))
+	if len(cfg.Persistence.FallbackPeers) == 0 {
+		cfg.Persistence.FallbackPeers = getDefaultBootstrapPeerIDs()
+	}
+
+	dht := makeDHT(ctx, h, cfg)
 
 	dht.proc = goprocessctx.WithContextAndTeardown(ctx, func() error {
 		// remove ourselves from network notifs.
 		dht.host.Network().StopNotify((*netNotifiee)(dht))
 		return nil
 	})
 
+	// fetch the last snapshot & try to seed RT
+	candidates, err := snapshotter.Load()
+	if err != nil {
+		logger.Warningf("error while loading snapshot of DHT routing table: %s, cannot seed dht", err)
+	} else if err := dht.seedRoutingTable(candidates, cfg.Persistence.FallbackPeers); err != nil {
+		logger.Warningf("error while seeding candidates to the routing table: %s", err)
+	}
+
+	// schedule periodic snapshots
+	sproc := periodicproc.Tick(cfg.Persistence.SnapshotInterval, func(proc goprocess.Process) {
+		logger.Debugf("storing snapshot of DHT routing table")
+		err := snapshotter.Store(dht.routingTable)
+		if err != nil {
+			logger.Warningf("error while storing snapshot of DHT routing table snapshot: %s", err)
+		}
+	})
+	dht.proc.AddChild(sproc)
+
+	// register for network notifs.
+	dht.host.Network().Notify((*netNotifiee)(dht))
+
 	dht.proc.AddChild(dht.providers.Process())
-	dht.Validator = cfg.Validator
 
 	if !cfg.Client {
 		for _, p := range cfg.Protocols {
@@ -152,9 +197,9 @@ func NewDHTClient(ctx context.Context, h host.Host, dstore ds.Batching) *IpfsDHT
 	return dht
 }
 
-func makeDHT(ctx context.Context, h host.Host, dstore ds.Batching, protocols []protocol.ID, bucketSize int) *IpfsDHT {
+func makeDHT(ctx context.Context, h host.Host, cfg *opts.Options) *IpfsDHT {
 	self := kb.ConvertPeerID(h.ID())
-	rt := kb.NewRoutingTable(bucketSize, self, time.Minute, h.Peerstore())
+	rt := kb.NewRoutingTable(cfg.BucketSize, self, time.Minute, h.Peerstore())
 	cmgr := h.ConnManager()
 
 	rt.PeerAdded = func(p peer.ID) {
@@ -167,22 +212,38 @@ func makeDHT(ctx context.Context, h host.Host, dstore ds.Batching, protocols []p
 	}
 
 	dht := &IpfsDHT{
-		datastore:        dstore,
+		datastore:        cfg.Datastore,
 		self:             h.ID(),
 		peerstore:        h.Peerstore(),
 		host:             h,
 		strmap:           make(map[peer.ID]*messageSender),
 		ctx:              ctx,
-		providers:        providers.NewProviderManager(ctx, h.ID(), dstore),
+		providers:        providers.NewProviderManager(ctx, h.ID(), cfg.Datastore),
 		birth:            time.Now(),
 		routingTable:     rt,
-		protocols:        protocols,
-		bucketSize:       bucketSize,
+		protocols:        cfg.Protocols,
+		bucketSize:       cfg.BucketSize,
 		triggerRtRefresh: make(chan chan<- error),
 	}
 
 	dht.ctx = dht.newContextWithLocalTags(ctx)
 
+	dht.Validator = cfg.Validator
+	dht.autoRefresh = cfg.RoutingTable.AutoRefresh
+	dht.rtRefreshPeriod = cfg.RoutingTable.RefreshPeriod
+	dht.rtRefreshQueryTimeout = cfg.RoutingTable.RefreshQueryTimeout
+
+	dht.maxRecordAge = cfg.MaxRecordAge
+	dht.enableProviders = cfg.EnableProviders
+	dht.enableValues = cfg.EnableValues
+	dht.bootstrapCfg = cfg.BootstrapConfig
+
+	dht.seedsProposer = cfg.Persistence.SeedsProposer
+	dht.seederDialTimeout = cfg.Persistence.SeederDialTimeout
+	dht.seederConcurrentDials = cfg.Persistence.SeederConcurrentDials
+	dht.seederRTSizeTarget = cfg.Persistence.SeederRTSizeTarget
+	dht.totalSeederTimeout = cfg.Persistence.TotalSeederTimeout
+
 	return dht
 }
 
@@ -193,7 +254,7 @@ func makeDHT(ctx context.Context, h host.Host, dstore ds.Batching, protocols []p
 	writeResp := func(errorChan chan error, err error) {
 		select {
 		case <-proc.Closing():
-		case errorChan <- errChan:
+		case errorChan <- err:
 		}
 		close(errorChan)
 	}
@@ -203,7 +264,7 @@ func makeDHT(ctx context.Context, h host.Host, dstore ds.Batching, protocols []p
 		case req := <-dht.rtRecoveryChan:
 			if dht.routingTable.Size() == 0 {
 				logger.Infof("rt recovery proc: received request with reqID=%s, RT is empty. initiating recovery", req.id)
-				// TODO Call Seeder with default bootstrap peers here once #383 is merged
+				// TODO Call SeedsProposer with default bootstrap peers here once #383 is merged
 				if dht.routingTable.Size() > 0 {
 					logger.Infof("rt recovery proc: successfully recovered RT for reqID=%s, RT size is now %d", req.id, dht.routingTable.Size())
 					go writeResp(req.errorChan, nil)
@@ -223,7 +284,6 @@ func makeDHT(ctx context.Context, h host.Host, dstore ds.Batching, protocols []p
 
 // putValueToPeer stores the given key/value pair at the peer 'p'
 func (dht *IpfsDHT) putValueToPeer(ctx context.Context, p peer.ID, rec *recpb.Record) error {
-
 	pmes := pb.NewMessage(pb.Message_PUT_VALUE, rec.Key, 0)
 	pmes.Record = rec
 	rpmes, err := dht.sendRequest(ctx, p, pmes)

dht_bootstrap.go

@@ -8,6 +8,7 @@ import (
 	multierror "github.com/hashicorp/go-multierror"
 	process "github.com/jbenet/goprocess"
 	processctx "github.com/jbenet/goprocess/context"
+	"github.com/libp2p/go-libp2p-core/peer"
 	"github.com/libp2p/go-libp2p-core/routing"
 	"github.com/multiformats/go-multiaddr"
 	_ "github.com/multiformats/go-multiaddr-dns"
@@ -43,6 +44,19 @@ func init() {
 	}
 }
 
+func getDefaultBootstrapPeerIDs() []peer.ID {
+	var defaultBootstrapPeerIDs []peer.ID
+	for i := range DefaultBootstrapPeers {
+		info, err := peer.AddrInfoFromP2pAddr(DefaultBootstrapPeers[i])
+		if err != nil {
+			logger.Errorf("failed to get peerID for peer with multiaddress %s: error is %s", DefaultBootstrapPeers[i].String(), err)
+			continue
+		}
+		defaultBootstrapPeerIDs = append(defaultBootstrapPeerIDs, info.ID)
+	}
+	return defaultBootstrapPeerIDs
+}
+
 // Start the refresh worker.
 func (dht *IpfsDHT) startRefreshing() error {
 	// scan the RT table periodically & do a random walk on k-buckets that haven't been queried since the given bucket period

dht_rt_seeder.go

@@ -0,0 +1,110 @@
+package dht
+
+import (
+	"context"
+	"sync"
+
+	"github.com/libp2p/go-libp2p-core/peer"
+)
+
+func (dht *IpfsDHT) seedRoutingTable(candidates, fallbacks []peer.ID) error {
+	seederCtx, cancel := context.WithTimeout(dht.ctx, dht.totalSeederTimeout)
+	defer cancel()
+
+	// filter out peers that are either NOT in the peer store OR already in the RT
+	findEligible := func(peers []peer.ID) []peer.ID {
+		var eligiblePeers []peer.ID
+		for _, p := range peers {
+
+			if dht.routingTable.Find(p) == p {
+				logger.Info("discarding candidate as it is already in the RT: %s", p)
+				continue
+			}
+
+			if addrs := dht.host.Peerstore().Addrs(p); len(addrs) == 0 {
+				logger.Infof("discarding candidate as we no longer have addresses: %s", p)
+				continue
+			}
+
+			eligiblePeers = append(eligiblePeers, p)
+		}
+		return eligiblePeers
+	}
+
+	// result of a dial attempt
+	type result struct {
+		p   peer.ID
+		err error
+	}
+
+	// rate-limit dials
+	semaphore := make(chan struct{}, dht.seederConcurrentDials)
+
+	// attempts to dial to a given peer to verify it's available
+	dialFn := func(ctx context.Context, p peer.ID, res chan<- result) {
+		childCtx, cancel := context.WithTimeout(ctx, dht.seederDialTimeout)
+		defer cancel()
+		_, err := dht.host.Network().DialPeer(childCtx, p)
+		select {
+		case <-ctx.Done(): // caller has already hung up & gone away
+		case res <- result{p, err}:
+		}
+	}
+
+	// ask the proposer to start proposing peers & write them on the peer channel
+	peersChan := dht.seedsProposer.Propose(seederCtx, dht.routingTable, findEligible(candidates), findEligible(fallbacks))
+
+	resCh := make(chan result) // dial results.
+
+	// start dialing to the peers received on the result channel
+	go func() {
+		defer close(resCh)
+
+		var wg sync.WaitGroup
+		for p := range peersChan {
+			select {
+			case <-seederCtx.Done():
+				return
+			default:
+				// start dialing
+				semaphore <- struct{}{}
+				wg.Add(1)
+				go func(p peer.ID, res chan<- result) {
+					dialFn(seederCtx, p, res)
+					<-semaphore
+					wg.Done()
+				}(p, resCh)
+			}
+		}
+		wg.Wait()
+
+	}()
+
+LOOP:
+	for {
+		select {
+		case res, hasMore := <-resCh:
+			if !hasMore {
+				logger.Infof("dht rt seeder: finished seeding RT with proposed peer set; RT size is now %d ",
+					dht.routingTable.Size())
+				break LOOP
+			}
+			if res.err != nil {
+				logger.Infof("dht rt seeder: discarded proposed peer due to dial error; peer ID: %s, err: %s", res.p, res.err)
+			} else {
+				if _, err := dht.routingTable.Update(res.p); err != nil {
+					logger.Warningf("dht rt seeder: failed to add proposed peer to routing table; peer ID: %s, err: %s", res.p, err)
+				}
+				if dht.routingTable.Size() >= dht.seederRTSizeTarget {
+					break LOOP
+				}
+			}
+
+		case <-seederCtx.Done():
+			logger.Info("dht rt seeder: finishing as we have exceeded the seeder timeout")
+			break LOOP
+		}
+	}
+
+	return nil
+}