Use longer TTL for pubsub seen messages

Once a message is received and validated, pubsub re-broadcasts it
to other peers and puts it into the seen messages cache. This way,
subsequent arrivals of the same message are not re-broadcasted
unnecessarily. This mechanism is important for the network to avoid
excessive message flooding. The default value used by libp2p is 2 minutes.
However, Keep client messaging sessions are quite time-consuming so,
we use a longer TTL of 5 minutes to reduce flooding risk even further. Worth
noting that this time cannot be too long as the cache may grow excessively and
impact memory consumption.

(cherry picked from commit a712112)

Author: lukasz-zimnoch

pkg/net/libp2p/channel_manager.go

@@ -17,6 +17,17 @@ import (
 const (
 	libp2pPeerOutboundQueueSize = 256
 	libp2pValidationQueueSize   = 4096
+	// libp2pSeenMessagesTTL is the time-to-live used for pubsub seen messages
+	// cache. Once a message is received and validated, pubsub re-broadcasts it
+	// to other peers and puts it into the seen messages cache. This way,
+	// subsequent arrivals of the same message are not re-broadcasted
+	// unnecessarily. This mechanism is important for the network to avoid
+	// excessive message flooding. The default value used by libp2p is 2 minutes.
+	// However, Keep client messaging sessions are quite time-consuming so,
+	// we use a longer TTL to reduce flooding risk even further. Worth noting
+	// that this time cannot be too long as the cache may grow excessively and
+	// impact memory consumption.
+	libp2pSeenMessagesTTL = 5 * time.Minute
 )
 
 type channelManager struct {
@@ -53,6 +64,7 @@ func newChannelManager(
 		pubsub.WithPeerOutboundQueueSize(libp2pPeerOutboundQueueSize),
 		pubsub.WithValidateQueueSize(libp2pValidationQueueSize),
 		pubsub.WithSeenMessagesStrategy(pubsubtc.Strategy_LastSeen),
+		pubsub.WithSeenMessagesTTL(libp2pSeenMessagesTTL),
 	)
 	if err != nil {
 		return nil, err