Save last seen peers and use them as bootstrap upon restart

cmd/start.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"fmt"
 	"time"
+	"strings"
+	"io/ioutil"
 
 	"github.com/ipfs/go-log"
 	"github.com/keep-network/keep-common/pkg/chain/ethereum/ethutil"
@@ -111,11 +113,25 @@ func Start(c *cli.Context) error {
 				"contract has been authorized to operate on the stake",
 		)
 	}
-
-	ctx := context.Background()
+	//Past the last seen peers file path to context for use in keep-core/libp2p.go
+	ctx := context.WithValue(context.Background(), "peersPath", c.GlobalString("peers"))
 	networkPrivateKey, _ := key.OperatorKeyToNetworkKey(
 		operatorPrivateKey, operatorPublicKey,
 	)
+
+	//Read last seen peers file as a bytearray and convert to a slice of strings
+	s, err := ioutil.ReadFile(c.GlobalString("peers"))
+	if err != nil {
+		logger.Debugf("Error reading last seen peers file")
+	}
+	lastSeenPeersString := string(s[:])
+	lastSeenPeers := strings.Split(lastSeenPeersString, ",")
+
+	//If the slice of last seen peers slice is non empty, use it as bootstrap peers list
+	if len(lastSeenPeers) != 0 {
+		config.LibP2P.Peers = lastSeenPeers
+	}
+
 	netProvider, err := libp2p.Connect(
 		ctx,
 		config.LibP2P,

main.go

@@ -13,13 +13,19 @@ import (
 	"github.com/urfave/cli"
 )
 
-const defaultConfigPath = "./config.toml"
+const (
+	defaultConfigPath = "./config.toml"
+	//Default path to last seen peers file
+	defaultPeersListPath = ".peers.dat"
+)
 
 var (
 	version  string
 	revision string
 
 	configPath string
+	//String for last seen peers path
+	peersListPath string
 
 	logger = log.Logger("keep-main")
 )
@@ -56,6 +62,13 @@ func main() {
 			Destination: &configPath,
 			Usage:       "full path to the configuration file",
 		},
+		//Define new flag to specify location of file where to store last seen peers
+		cli.StringFlag{
+			Name: "peers",
+			Value: defaultPeersListPath,
+			Destination: &peersListPath,
+			Usage: "full path to the last connected peers list file"
+		},
 	}
 	app.Commands = []cli.Command{
 		cmd.StartCommand,

pkg/net/libp2p/libp2p.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"sync"
 	"time"
+	"io/ioutil"
+	"strings"
 
 	"github.com/ipfs/go-log"
 
@@ -219,6 +221,32 @@ func (cm *connectionManager) monitorConnectedPeers(ctx context.Context) {
 		case <-ticker.C:
 			connectedPeers := cm.ConnectedPeers()
 
+			//Slice for connected peers' addresses strings
+			var addrStrings []string
+			//Loop over connected peers' IDs
+			for _, peerID := range cm.Network().Peers() {
+				//PeerInfo gets a struc containing ID + array of multiaddresses for a given peer
+				info := cm.Peerstore().PeerInfo(peerID)
+				//Get multiaddresses for the current peer
+				peerAddrStrings := make([]string, 0, len(info.Addrs))
+				//For the set of multiaddresses of the current peer, construct an array of valid transport addresses strings
+				for _, multiaddr := range info.Addrs {
+					peerAddrStrings = append(peerAddrStrings, multiaddressWithIdentity(multiaddr, peerID))
+				}
+				//Append to slice of addresses of all connected peers
+				addrStrings = append(addrStrings, peerAddrStrings...)
+			}  
+
+			//Get string of file path to write to
+			peersPath := fmt.Sprintf("%v", ctx.Value("peersPath"))
+			//Convert addresses slice to splitted string
+			addresses := strings.Join(addrStrings, ",")
+			//Write addresses string in specified file
+			err := ioutil.WriteFile(peersPath, []byte(addresses), 0644)
+			if err != nil {
+				logger.Debugf("Error writing peers addresses to file")
+			}
+
 			logger.Infof("number of connected peers: [%v]", len(connectedPeers))
 			logger.Debugf("connected peers: [%v]", connectedPeers)
 		case <-ctx.Done():