refactor(kademlia): add peers at start asynchronously (#2082)

pkg/topology/kademlia/kademlia.go

@@ -9,7 +9,6 @@ import (
 	random "crypto/rand"
 	"encoding/json"
 	"errors"
-	"fmt"
 	"math"
 	"math/big"
 	"math/bits"
@@ -570,12 +569,25 @@ func (k *Kad) Start(_ context.Context) error {
 	k.wg.Add(1)
 	go k.manage()
 
-	addresses, err := k.addressBook.Overlays()
-	if err != nil {
-		return fmt.Errorf("addressbook overlays: %w", err)
-	}
+	go func() {
+		select {
+		case <-k.halt:
+			return
+		case <-k.quit:
+			return
+		default:
+		}
+
+		start := time.Now()
+		addresses, err := k.addressBook.Overlays()
+		if err != nil {
+			k.logger.Errorf("addressbook overlays: %w", err)
+			return
+		}
+		k.AddPeers(addresses...)
+		k.metrics.StartAddAddressBookOverlaysTime.Observe(float64(time.Since(start).Nanoseconds()))
+	}()
 
-	k.AddPeers(addresses...)
 	return nil
 }
 

pkg/topology/kademlia/kademlia_test.go

@@ -807,6 +807,8 @@ func TestAddressBookQuickPrune(t *testing.T) {
 	}
 	defer kad.Close()
 
+	time.Sleep(100 * time.Millisecond)
+
 	nonConnPeer, err := bzz.NewAddress(signer, nonConnectableAddress, test.RandomAddressAt(base, 1), 0)
 	if err != nil {
 		t.Fatal(err)

pkg/topology/kademlia/metrics.go

@@ -26,6 +26,7 @@ type metrics struct {
 	TotalOutboundConnectionAttempts       prometheus.Counter
 	TotalOutboundConnectionFailedAttempts prometheus.Counter
 	TotalBootNodesConnectionAttempts      prometheus.Counter
+	StartAddAddressBookOverlaysTime       prometheus.Histogram
 }
 
 // newMetrics is a convenient constructor for creating new metrics.
@@ -122,7 +123,14 @@ func newMetrics() metrics {
 			Subsystem: subsystem,
 			Name:      "total_bootnodes_connection_attempts",
 			Help:      "Total boot-nodes connection attempts made.",
-		})}
+		}),
+		StartAddAddressBookOverlaysTime: prometheus.NewHistogram(prometheus.HistogramOpts{
+			Namespace: m.Namespace,
+			Subsystem: subsystem,
+			Name:      "start_add_addressbook_overlays_time",
+			Help:      "The time spent adding overlays peers from addressbook on kademlia start.",
+		}),
+	}
 }
 
 // Metrics returns set of prometheus collectors.