Give peers a chance (#4268)

* Add decay function for peer badresponses count
* Activate peer decay in p2p

beacon-chain/p2p/BUILD.bazel

@@ -16,6 +16,7 @@ go_library(
         "log.go",
         "monitoring.go",
         "options.go",
+        "peer_decay.go",
         "rpc_topic_mappings.go",
         "sender.go",
         "service.go",

beacon-chain/p2p/peer_decay.go

@@ -0,0 +1,25 @@
+package p2p
+
+import (
+	"context"
+	"time"
+
+	"github.com/prysmaticlabs/prysm/beacon-chain/p2p/peers"
+)
+
+// starPeerDecay starts a loop that periodically decays the bad response count of peers, giving reformed peers a chance to rejoin
+// the network.
+// This runs every hour.
+func startPeerDecay(ctx context.Context, peers *peers.Status) {
+	go (func() {
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			default:
+				peers.Decay()
+				time.Sleep(1 * time.Hour)
+			}
+		}
+	})()
+}

beacon-chain/p2p/peers/status.go

@@ -303,6 +303,19 @@ func (p *Status) All() []peer.ID {
 	return pids
 }
 
+// Decay reduces the bad responses of all peers, giving reformed peers a chance to join the network.
+// This can be run periodically, although note that each time it runs it does give all bad peers another chance as well to clog up
+// the network with bad responses, so should not be run too frequently; once an hour would be reasonable.
+func (p *Status) Decay() {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	for _, status := range p.status {
+		if status.badResponses > 0 {
+			status.badResponses--
+		}
+	}
+}
+
 // fetch is a helper function that fetches a peer status, possibly creating it.
 func (p *Status) fetch(pid peer.ID) *peerStatus {
 	if _, ok := p.status[pid]; !ok {

beacon-chain/p2p/peers/status_test.go

@@ -302,8 +302,40 @@ func TestPeerConnectionStatuses(t *testing.T) {
 	}
 }
 
+func TestDecay(t *testing.T) {
+	maxBadResponses := 2
+	p := peers.NewStatus(maxBadResponses)
+
+	// Peer 1 has 0 bad responses.
+	pid1 := addPeer(t, p, peers.PeerConnected)
+	// Peer 2 has 1 bad response.
+	pid2 := addPeer(t, p, peers.PeerConnected)
+	p.IncrementBadResponses(pid2)
+	// Peer 3 has 2 bad response.
+	pid3 := addPeer(t, p, peers.PeerConnected)
+	p.IncrementBadResponses(pid3)
+	p.IncrementBadResponses(pid3)
+
+	// Decay the values
+	p.Decay()
+
+	// Ensure the new values are as expected
+	badResponses1, _ := p.BadResponses(pid1)
+	if badResponses1 != 0 {
+		t.Errorf("Unexpected bad responses for peer 0: expected 0, received %v", badResponses1)
+	}
+	badResponses2, _ := p.BadResponses(pid2)
+	if badResponses2 != 0 {
+		t.Errorf("Unexpected bad responses for peer 0: expected 0, received %v", badResponses2)
+	}
+	badResponses3, _ := p.BadResponses(pid3)
+	if badResponses3 != 1 {
+		t.Errorf("Unexpected bad responses for peer 0: expected 0, received %v", badResponses3)
+	}
+}
+
 // addPeer is a helper to add a peer with a given connection state)
-func addPeer(t *testing.T, p *peers.Status, state peers.PeerConnectionState) {
+func addPeer(t *testing.T, p *peers.Status, state peers.PeerConnectionState) peer.ID {
 	// Set up some peers with different states
 	mhBytes := []byte{0x11, 0x04}
 	idBytes := make([]byte, 4)
@@ -315,4 +347,5 @@ func addPeer(t *testing.T, p *peers.Status, state peers.PeerConnectionState) {
 	}
 	p.Add(id, nil, network.DirUnknown)
 	p.SetConnectionState(id, state)
+	return id
 }

beacon-chain/p2p/service.go

@@ -204,6 +204,7 @@ func (s *Service) Start() {
 	}
 
 	startPeerWatcher(s.ctx, s.host, peersToWatch...)
+	startPeerDecay(s.ctx, s.peers)
 	registerMetrics(s)
 	multiAddrs := s.host.Network().ListenAddresses()
 	logIP4Addr(s.host.ID(), multiAddrs...)