feat(federation): add load balanced option (#2915)

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/p2p/federated.go

@@ -4,12 +4,44 @@ const FederatedID = "federated"
 
 type FederatedServer struct {
 	listenAddr, service, p2ptoken string
+	requestTable                  map[string]int
+	loadBalanced                  bool
 }
 
-func NewFederatedServer(listenAddr, service, p2pToken string) *FederatedServer {
+func NewFederatedServer(listenAddr, service, p2pToken string, loadBalanced bool) *FederatedServer {
 	return &FederatedServer{
-		listenAddr: listenAddr,
-		service:    service,
-		p2ptoken:   p2pToken,
+		listenAddr:   listenAddr,
+		service:      service,
+		p2ptoken:     p2pToken,
+		requestTable: map[string]int{},
+		loadBalanced: loadBalanced,
+	}
+}
+
+func (fs *FederatedServer) SelectLeastUsedServer() string {
+	// cycle over requestTable and find the entry with the lower number
+	// if there are multiple entries with the same number, select one randomly
+	// if there are no entries, return an empty string
+	var min int
+	var minKey string
+	for k, v := range fs.requestTable {
+		if min == 0 || v < min {
+			min = v
+			minKey = k
+		}
+	}
+	return minKey
+}
+
+func (fs *FederatedServer) RecordRequest(nodeID string) {
+	// increment the counter for the nodeID in the requestTable
+	fs.requestTable[nodeID]++
+}
+
+func (fs *FederatedServer) EnsureRecordExist(nodeID string) {
+	// if the nodeID is not in the requestTable, add it with a counter of 0
+	_, ok := fs.requestTable[nodeID]
+	if !ok {
+		fs.requestTable[nodeID] = 0
 	}
 }

core/p2p/federated_server.go

@@ -100,10 +100,23 @@ func (fs *FederatedServer) proxy(ctx context.Context, node *node.Node) error {
 					return
 				}
 
-				// open a TCP stream to one of the tunnels
-				// chosen randomly
-				// TODO: optimize this and track usage
-				tunnelAddr := tunnelAddresses[rand.IntN(len(tunnelAddresses))]
+				tunnelAddr := ""
+
+				if fs.loadBalanced {
+					for _, t := range tunnelAddresses {
+						fs.EnsureRecordExist(t)
+					}
+
+					tunnelAddr = fs.SelectLeastUsedServer()
+					log.Debug().Msgf("Selected tunnel %s", tunnelAddr)
+					if tunnelAddr == "" {
+						tunnelAddr = tunnelAddresses[rand.IntN(len(tunnelAddresses))]
+					}
+
+					fs.RecordRequest(tunnelAddr)
+				} else {
+					tunnelAddr = tunnelAddresses[rand.IntN(len(tunnelAddresses))]
+				}
 
 				tunnelConn, err := net.Dial("tcp", tunnelAddr)
 				if err != nil {