Removing peer state connectServices not in exported-service-list (#23377)

* Removing peer state connectServices not in exported-service-list

* Addition of comment

* Addition of comment line

* Addition of comment lines

* Addition of comment lines

Author: pajay-rao

agent/grpc-external/services/peerstream/subscription_manager.go

@@ -494,8 +494,18 @@ func (m *subscriptionManager) syncDiscoveryChains(
 		m.collectPendingEventForDiscoveryChain(state, pending, chainName, info)
 	}
 
+	exportedServicesMap := make(map[structs.ServiceName]struct{}, len(state.exportList.Services))
+	for _, m := range state.exportList.Services {
+		exportedServicesMap[m] = struct{}{}
+	}
+
 	// if it was dropped, try to emit an DELETE event
 	for chainName := range state.connectServices {
+		// Deleting stale peer state connect service entry not in exported-service-list
+		if _, ok := exportedServicesMap[chainName]; !ok {
+			delete(state.connectServices, chainName)
+		}
+
 		if _, ok := chainsByName[chainName]; ok {
 			continue
 		}

agent/grpc-external/services/peerstream/subscription_state.go

@@ -25,10 +25,12 @@ type subscriptionState struct {
 	// partition is immutable
 	partition string
 
-	// plain data
+	// exportList stores the central state list of latest exported-service-list services to the peer
 	exportList *structs.ExportedServiceList
 
 	watchedServices map[structs.ServiceName]context.CancelFunc
+
+	// connectServices stores latest map of synthetic discovery chain replies.
 	connectServices map[structs.ServiceName]structs.ExportedDiscoveryChainInfo
 
 	// eventVersions is a duplicate event suppression system keyed by the "id"