p2p: add spread to the discovery advertisement interval (#5815)

## Motivation

Need to lessen DHT overload from the routing discovery mechanism

CHANGELOG.md

@@ -16,6 +16,8 @@ See [RELEASE](./RELEASE.md) for workflow instructions.
 
 * [#5803](https://github.com/spacemeshos/go-spacemesh/pull/5803) Fixed PoST verifiers autoscaling for 1:N setups.
 
+* [#5815](https://github.com/spacemeshos/go-spacemesh/pull/5815) Add spread to the discovery advertisement interval.
+
 ### Features
 
 ## Release v1.4.4

p2p/dhtdiscovery/discovery.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math/rand/v2"
 	"sync"
 	"time"
 
@@ -28,6 +29,7 @@ const (
 	discoveryHighPeersDelay = 10 * time.Second
 	protocolPrefix          = "/spacekad"
 	ProtocolID              = protocolPrefix + "/kad/1.0.0"
+	recheckInterval         = time.Minute
 )
 
 type Opt func(*Discovery)
@@ -140,6 +142,12 @@ func WithAdvertiseInterval(value time.Duration) Opt {
 	}
 }
 
+func WithAdvertiseIntervalSpread(value time.Duration) Opt {
+	return func(d *Discovery) {
+		d.advertiseIntervalSpread = value
+	}
+}
+
 func WithFindPeersRetryDelay(value time.Duration) Opt {
 	return func(d *Discovery) {
 		d.findPeersRetryDelay = value
@@ -197,14 +205,15 @@ type Discovery struct {
 	// how often to check if we have enough peers
 	period time.Duration
 	// timeout used for connections
-	timeout             time.Duration
-	bootstrapDuration   time.Duration
-	minPeers, highPeers int
-	backup, bootnodes   []peer.AddrInfo
-	advertiseDelay      time.Duration
-	advertiseInterval   time.Duration
-	advertiseRetryDelay time.Duration
-	findPeersRetryDelay time.Duration
+	timeout                 time.Duration
+	bootstrapDuration       time.Duration
+	minPeers, highPeers     int
+	backup, bootnodes       []peer.AddrInfo
+	advertiseDelay          time.Duration
+	advertiseInterval       time.Duration
+	advertiseIntervalSpread time.Duration
+	advertiseRetryDelay     time.Duration
+	findPeersRetryDelay     time.Duration
 }
 
 func (d *Discovery) FindPeer(ctx context.Context, p peer.ID) (peer.AddrInfo, error) {
@@ -395,6 +404,14 @@ func (d *Discovery) peerHasTag(p peer.ID) bool {
 	return found
 }
 
+func (d *Discovery) advInterval() time.Duration {
+	if d.advertiseIntervalSpread == 0 {
+		return d.advertiseInterval
+	}
+
+	return d.advertiseInterval - d.advertiseIntervalSpread + rand.N(2*d.advertiseIntervalSpread)
+}
+
 func (d *Discovery) advertiseNS(ctx context.Context, ns string, active func() bool) error {
 	if d.advertiseDelay != 0 {
 		select {
@@ -408,13 +425,16 @@ func (d *Discovery) advertiseNS(ctx context.Context, ns string, active func() bo
 		if active == nil || active() {
 			var err error
 			d.logger.Debug("advertising for routing discovery", zap.String("ns", ns))
-			ttl, err = d.disc.Advertise(ctx, ns, p2pdisc.TTL(d.advertiseInterval))
+			ttl, err = d.disc.Advertise(ctx, ns, p2pdisc.TTL(d.advInterval()))
 			if err != nil {
 				d.logger.Error("failed to re-advertise for discovery", zap.String("ns", ns), zap.Error(err))
 				ttl = d.advertiseRetryDelay
 			}
 		} else {
-			ttl = d.advertiseInterval
+			// At this moment, advertisement is not needed.
+			// There was previous delay already, just need to recheck if we need
+			// to start advertising again
+			ttl = recheckInterval
 		}
 		select {
 		case <-ctx.Done():

p2p/host.go

@@ -96,10 +96,11 @@ func DefaultConfig() Config {
 			ResetPeriod: time.Minute,
 		},
 		DiscoveryTimings: DiscoveryTimings{
-			AdvertiseDelay:      time.Hour,
-			AdvertiseInterval:   time.Hour,
-			AdvertiseRetryDelay: time.Minute,
-			FindPeersRetryDelay: time.Minute,
+			AdvertiseDelay:          time.Hour,
+			AdvertiseInterval:       2 * time.Hour,
+			AdvertiseIntervalSpread: time.Hour,
+			AdvertiseRetryDelay:     time.Minute,
+			FindPeersRetryDelay:     time.Minute,
 		},
 	}
 }
@@ -161,10 +162,11 @@ type Config struct {
 }
 
 type DiscoveryTimings struct {
-	AdvertiseDelay      time.Duration `mapstructure:"advertise-delay"`
-	AdvertiseInterval   time.Duration `mapstructure:"advertise-interval"`
-	AdvertiseRetryDelay time.Duration `mapstructure:"advertise-retry-delay"`
-	FindPeersRetryDelay time.Duration `mapstructure:"find-peers-retry-delay"`
+	AdvertiseDelay          time.Duration `mapstructure:"advertise-delay"`
+	AdvertiseInterval       time.Duration `mapstructure:"advertise-interval"`
+	AdvertiseIntervalSpread time.Duration `mapstructure:"advertise-interval-spread"`
+	AdvertiseRetryDelay     time.Duration `mapstructure:"advertise-retry-delay"`
+	FindPeersRetryDelay     time.Duration `mapstructure:"find-peers-retry-delay"`
 }
 
 type AutoNATServer struct {
@@ -209,6 +211,10 @@ func (cfg *Config) Validate() error {
 		}
 	}
 
+	if cfg.DiscoveryTimings.AdvertiseIntervalSpread > cfg.DiscoveryTimings.AdvertiseInterval {
+		return errors.New("advertise-interval-spread cannot be greater than advertise-interval")
+	}
+
 	return nil
 }
 

p2p/upgrade.go

@@ -164,6 +164,7 @@ func Upgrade(h host.Host, opts ...Opt) (*Host, error) {
 		discovery.WithLogger(fh.logger.Zap()),
 		discovery.WithAdvertiseDelay(fh.cfg.DiscoveryTimings.AdvertiseDelay),
 		discovery.WithAdvertiseInterval(fh.cfg.DiscoveryTimings.AdvertiseInterval),
+		discovery.WithAdvertiseIntervalSpread(fh.cfg.DiscoveryTimings.AdvertiseIntervalSpread),
 		discovery.WithAdvertiseRetryDelay(fh.cfg.DiscoveryTimings.AdvertiseInterval),
 		discovery.WithFindPeersRetryDelay(fh.cfg.DiscoveryTimings.FindPeersRetryDelay),
 	}