Added option to set DHT to client mode only and configure the cleanup interval

Author: icellan

client.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/libp2p/go-libp2p"
 	dht "github.com/libp2p/go-libp2p-kad-dht"
+	"github.com/libp2p/go-libp2p-kad-dht/records"
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
 	"github.com/libp2p/go-libp2p/core/crypto"
 	"github.com/libp2p/go-libp2p/core/host"
@@ -27,6 +28,9 @@ import (
 	"github.com/libp2p/go-libp2p/p2p/discovery/mdns"
 	drouting "github.com/libp2p/go-libp2p/p2p/discovery/routing"
 	"github.com/multiformats/go-multiaddr"
+
+	ds "github.com/ipfs/go-datastore"
+	dssync "github.com/ipfs/go-datastore/sync"
 )
 
 var (
@@ -92,7 +96,7 @@ func NewClient(config Config) (Client, error) {
 	}
 
 	// Set up DHT
-	kadDHT, err := setupDHT(ctx, h, bootstrapPeers, clientLogger, cancel)
+	kadDHT, err := setupDHT(ctx, h, config, bootstrapPeers, clientLogger, cancel)
 	if err != nil {
 		return nil, err
 	}
@@ -204,8 +208,46 @@ func createHost(_ context.Context, hostOpts []libp2p.Option, config Config, rela
 	return h, nil
 }
 
-func setupDHT(ctx context.Context, h host.Host, bootstrapPeers []peer.AddrInfo, _ logger, cancel context.CancelFunc) (*dht.IpfsDHT, error) {
-	kadDHT, err := dht.New(ctx, h, dht.Mode(dht.ModeServer), dht.BootstrapPeers(bootstrapPeers...))
+func setupDHT(ctx context.Context, h host.Host, config Config, bootstrapPeers []peer.AddrInfo, log logger, cancel context.CancelFunc) (*dht.IpfsDHT, error) {
+	// Determine DHT mode (default to server)
+	mode := dht.ModeServer
+	if config.DHTMode == "client" {
+		mode = dht.ModeClient
+		log.Infof("DHT mode: client (query-only, no provider storage)")
+	} else {
+		log.Infof("DHT mode: server (will advertise and store provider records)")
+	}
+
+	// Build DHT options
+	dhtOpts := []dht.Option{
+		dht.Mode(mode),
+		dht.BootstrapPeers(bootstrapPeers...),
+	}
+
+	// If server mode and custom cleanup interval specified, configure ProviderManager
+	if mode == dht.ModeServer && config.DHTCleanupInterval > 0 {
+		log.Infof("Configuring DHT cleanup interval: %v", config.DHTCleanupInterval)
+
+		// Create an in-memory datastore for the provider manager
+		// Same as default DHT datastore creation
+		datastore := dssync.MutexWrap(ds.NewMapDatastore())
+
+		providerManager, err := records.NewProviderManager(
+			ctx,
+			h.ID(),
+			h.Peerstore(),
+			datastore,
+			records.CleanupInterval(config.DHTCleanupInterval),
+		)
+		if err != nil {
+			_ = h.Close()
+			cancel()
+			return nil, fmt.Errorf("failed to create provider manager: %w", err)
+		}
+		dhtOpts = append(dhtOpts, dht.ProviderStore(providerManager))
+	}
+
+	kadDHT, err := dht.New(ctx, h, dhtOpts...)
 	if err != nil {
 		_ = h.Close()
 		cancel()

config.go

@@ -79,4 +79,22 @@ type Config struct {
 	// If not provided, bootstrap peers will be used as relays.
 	// Example: []string{"/ip4/1.2.3.4/tcp/4001/p2p/QmPeerID"}
 	RelayPeers []string
+
+	// DHTMode specifies whether this node runs the DHT in client or server mode.
+	// Valid values: "client", "server"
+	// - "client": Can query DHT but doesn't advertise itself or store provider records.
+	//             No ProviderManager cleanup overhead.
+	// - "server": Participates fully in DHT, advertises itself, stores provider records.
+	//             Has periodic cleanup overhead. Default mode for proper P2P networks.
+	// If not provided or empty, defaults to "server" mode.
+	DHTMode string
+
+	// DHTCleanupInterval is the interval at which the DHT's ProviderManager performs
+	// garbage collection of expired provider records. The cleanup involves querying all
+	// provider records and removing expired entries.
+	// Only applies when DHTMode is "server".
+	// If not provided or zero, uses the DHT default (1 hour).
+	// Recommended: 6-24 hours for production to reduce CPU overhead.
+	// The cleanup frequency trades off between memory usage (stale records) and CPU usage.
+	DHTCleanupInterval time.Duration
 }