eth: track peer revisions in the sync loop

Author: vbhattaccmu

eth/sync.go

@@ -61,8 +61,8 @@ type chainSyncer struct {
 	peerEventCh chan struct{}
 	doneCh      chan error // non-nil when sync is running
 
-	peersUnavailableUntil      time.Time
-	peersUnavailableAtRevision uint64
+	peersUnavailableUntil time.Time
+	observedPeerRevision  uint64
 }
 
 // chainSyncOp is a scheduled sync operation.
@@ -143,7 +143,6 @@ func (cs *chainSyncer) onSyncDone(err error) {
 
 	if errors.Is(err, downloader.ErrPeersUnavailable) || errors.Is(err, downloader.ErrPeerBackedOff) || errors.Is(err, whitelist.ErrNoRemote) {
 		cs.peersUnavailableUntil = time.Now().Add(forceSyncCycle)
-		cs.peersUnavailableAtRevision = cs.handler.peers.currentRevision()
 	} else {
 		cs.peersUnavailableUntil = time.Time{}
 	}
@@ -159,9 +158,11 @@ func (cs *chainSyncer) onSyncDone(err error) {
 }
 
 func (cs *chainSyncer) onPeerEvent() {
-	if !cs.peersUnavailableUntil.IsZero() && cs.handler.peers.currentRevision() != cs.peersUnavailableAtRevision {
+	revision := cs.handler.peers.currentRevision()
+	if !cs.peersUnavailableUntil.IsZero() && revision != cs.observedPeerRevision {
 		cs.peersUnavailableUntil = time.Time{}
 	}
+	cs.observedPeerRevision = revision
 }
 
 func (cs *chainSyncer) shutdown() {

eth/sync_test.go

@@ -195,6 +195,7 @@ func TestChainSyncerCooldownSurvivesBlockAnnounce(t *testing.T) {
 	if err := handler.downloader.RegisterPeer(peer.ID(), eth.ETH68, &ethPeer{Peer: peer}); err != nil {
 		t.Fatal(err)
 	}
+	syncer.onPeerEvent()
 
 	syncer.onSyncDone(downloader.ErrPeersUnavailable)
 	if syncer.peersUnavailableUntil.IsZero() {
@@ -216,6 +217,7 @@ func TestChainSyncerCooldownSurvivesBlockAnnounce(t *testing.T) {
 	if handler.peers.len() != 1 {
 		t.Fatalf("peer replacement should preserve peer count, have %d", handler.peers.len())
 	}
+	syncer.onSyncDone(downloader.ErrPeersUnavailable)
 	syncer.onPeerEvent()
 	if !syncer.peersUnavailableUntil.IsZero() {
 		t.Fatal("a peer replacement must clear the cooldown")