Listen to two random attestation subnets (#12254)

randomly choosing two attestation subnets and subscribing indefinitely.

Co-authored-by: shota.silagadze <[email protected]>

cl/sentinel/service/start.go

@@ -19,6 +19,7 @@ package service
 import (
 	"context"
 	"fmt"
+	"math/rand/v2"
 	"net"
 	"strings"
 	"time"
@@ -41,6 +42,8 @@ import (
 	"github.com/erigontech/erigon/cl/cltypes"
 )
 
+const AttestationSubnetSubscriptions = 2
+
 type ServerConfig struct {
 	Network       string
 	Addr          string
@@ -56,6 +59,12 @@ func generateSubnetsTopics(template string, maxIds int) []sentinel.GossipTopic {
 			CodecStr: sentinel.SSZSnappyCodec,
 		})
 	}
+
+	if template == gossip.TopicNamePrefixBeaconAttestation {
+		rand.Shuffle(len(topics), func(i, j int) {
+			topics[i], topics[j] = topics[j], topics[i]
+		})
+	}
 	return topics
 }
 
@@ -112,12 +121,16 @@ func createSentinel(
 			gossip.TopicNamePrefixBlobSidecar,
 			int(cfg.BeaconConfig.MaxBlobsPerBlock),
 		)...)
+
+	attestationSubnetTopics := generateSubnetsTopics(
+		gossip.TopicNamePrefixBeaconAttestation,
+		int(cfg.NetworkConfig.AttestationSubnetCount),
+	)
+
 	gossipTopics = append(
 		gossipTopics,
-		generateSubnetsTopics(
-			gossip.TopicNamePrefixBeaconAttestation,
-			int(cfg.NetworkConfig.AttestationSubnetCount),
-		)...)
+		attestationSubnetTopics[AttestationSubnetSubscriptions:]...)
+
 	gossipTopics = append(
 		gossipTopics,
 		generateSubnetsTopics(
@@ -137,6 +150,17 @@ func createSentinel(
 			logger.Error("[Sentinel] failed to start sentinel", "err", err)
 		}
 	}
+
+	for k := 0; k < AttestationSubnetSubscriptions; k++ {
+		if err := sent.Unsubscribe(attestationSubnetTopics[k]); err != nil {
+			logger.Error("[Sentinel] failed to start sentinel", "err", err)
+			continue
+		}
+		_, err := sent.SubscribeGossip(attestationSubnetTopics[k], time.Unix(0, math.MaxInt64)) // Listen forever.
+		if err != nil {
+			logger.Error("[Sentinel] failed to start sentinel", "err", err)
+		}
+	}
 	return sent, nil
 }