43-use-gravestones

Change of approach from keepalive to a noiseless protocol

pkg/sync/syncer.go

@@ -1,8 +1,8 @@
 package sync
 
 import (
+	"io"
 	"math/rand"
-	"sync"
 	"time"
 
 	"github.com/tim-beatham/wgmesh/pkg/conf"
@@ -59,36 +59,42 @@ func (s *SyncerImpl) Sync(meshId string) error {
 
 	if len(nodeNames) > s.conf.ClusterSize && rand.Float64() < s.conf.InterClusterChance {
 		logging.Log.WriteInfof("Sending to random cluster")
-		interCluster := s.cluster.GetInterCluster(nodeNames, publicKey.String())
-		randomSubset = append(randomSubset, interCluster)
+		randomSubset[len(randomSubset)-1] = s.cluster.GetInterCluster(nodeNames, publicKey.String())
 	}
 
-	var waitGroup sync.WaitGroup
+	var succeeded bool = false
 
-	for index := range randomSubset {
-		waitGroup.Add(1)
+	// Do this synchronously to conserve bandwidth
+	for _, node := range randomSubset {
+		correspondingPeer := s.manager.GetNode(meshId, node)
 
-		go func(i int) error {
-			defer waitGroup.Done()
+		if correspondingPeer == nil {
+			logging.Log.WriteErrorf("node %s does not exist", node)
+		}
 
-			correspondingPeer := s.manager.GetNode(meshId, randomSubset[i])
+		err = s.requester.SyncMesh(meshId, correspondingPeer.GetHostEndpoint())
 
-			if correspondingPeer == nil {
-				logging.Log.WriteErrorf("node %s does not exist", randomSubset[i])
-			}
-
-			err := s.requester.SyncMesh(meshId, correspondingPeer.GetHostEndpoint())
-			return err
-		}(index)
+		if err == nil || err == io.EOF {
+			succeeded = true
+		} else {
+			// If the synchronisation operation has failed them mark a gravestone
+			// preventing the peer from being re-contacted until it has updated
+			// itself
+			s.manager.GetMesh(meshId).Mark(node)
+		}
 	}
 
-	waitGroup.Wait()
-
 	s.syncCount++
 	logging.Log.WriteInfof("SYNC TIME: %v", time.Since(before))
 	logging.Log.WriteInfof("SYNC COUNT: %d", s.syncCount)
 
 	s.infectionCount = ((s.conf.InfectionCount + s.infectionCount - 1) % s.conf.InfectionCount)
+
+	if !succeeded {
+		// If could not gossip with anyone then repeat.
+		s.infectionCount++
+	}
+
 	s.manager.GetMesh(meshId).SaveChanges()
 	return nil
 }