feat(NetworkIdentity): Reuse Network IDs

Assets/Mirror/Core/NetworkIdentity.cs

@@ -269,17 +269,52 @@ internal static void ResetClientStatics()
 
         internal static void ResetServerStatics()
         {
+            reuseNetworkIds = true;
+            reuseDelay = 1;
+
+            netIdQueue.Clear();
             nextNetworkId = 1;
         }
 
         /// <summary>Gets the NetworkIdentity from the sceneIds dictionary with the corresponding id</summary>
         public static NetworkIdentity GetSceneIdentity(ulong id) => sceneIds[id];
 
+        #region Network ID Reuse
+
+        internal static bool reuseNetworkIds = true;
+        internal static byte reuseDelay = 1;
+
+        internal struct ReusableNetworkId
+        {
+            public uint reusableNetId;
+            public double timeAvailable;
+        }
+
+        // pool of NetworkIds that can be reused
+        internal static readonly Queue<ReusableNetworkId> netIdQueue = new Queue<ReusableNetworkId>();
         static uint nextNetworkId = 1;
-        internal static uint GetNextNetworkId() => nextNetworkId++;
+
+        internal static uint GetNextNetworkId()
+        {
+            // Older Unity versions don't have TryPeek.
+            if (reuseNetworkIds && netIdQueue.Count > 0 && netIdQueue.Peek().timeAvailable < NetworkTime.time)
+            {
+                ReusableNetworkId nextNetId = netIdQueue.Dequeue();
+                //Debug.LogFormat(LogType.Log, LogOption.NoStacktrace, null, $"[GetNextNetworkId] Reusing NetworkId {nextNetId.reusableNetId}.");
+                return nextNetId.reusableNetId;
+            }
+
+            return nextNetworkId++;
+        }
 
         /// <summary>Resets nextNetworkId = 1</summary>
-        public static void ResetNextNetworkId() => nextNetworkId = 1;
+        public static void ResetNextNetworkId()
+        {
+            netIdQueue.Clear();
+            nextNetworkId = 1;
+        }
+
+        #endregion
 
         /// <summary>The delegate type for the clientAuthorityCallback.</summary>
         public delegate void ClientAuthorityCallback(NetworkConnectionToClient conn, NetworkIdentity identity, bool authorityState);
@@ -633,6 +668,9 @@ void OnDestroy()
                 NetworkServer.Destroy(gameObject);
             }
 
+            if (isServer && reuseNetworkIds && netId > 0)
+                netIdQueue.Enqueue(new ReusableNetworkId { reusableNetId = netId, timeAvailable = NetworkTime.time + reuseDelay });
+
             if (isLocalPlayer)
             {
                 // previously there was a bug where isLocalPlayer was
@@ -1327,7 +1365,14 @@ internal void ResetState()
             isOwned = false;
             NotifyAuthority();
 
-            netId = 0;
+            if (netId > 0)
+            {
+                if (reuseNetworkIds)
+                    netIdQueue.Enqueue(new ReusableNetworkId { reusableNetId = netId, timeAvailable = NetworkTime.time + reuseDelay });
+
+                netId = 0;
+            }
+
             connectionToServer = null;
             connectionToClient = null;
 

Assets/Mirror/Core/NetworkManager.cs

@@ -47,6 +47,13 @@ public class NetworkManager : MonoBehaviour
         // [Tooltip("Client broadcasts 'sendRate' times per second. Use around 60Hz for fast paced games like Counter-Strike to minimize latency. Use around 30Hz for games like WoW to minimize computations. Use around 1-10Hz for slow paced games like EVE.")]
         // public int clientSendRate = 30; // 33 ms
 
+        [Header("Network ID Reuse")]
+        [Tooltip("Reuse network IDs when objects are unspawned or destroyed?")]
+        public bool reuseNetworkIds = true;
+        [Range(1, 60)]
+        [Tooltip("Delay in seconds before network IDs are reused")]
+        public byte reuseDelay = 1;
+
         /// <summary>Automatically switch to this scene upon going offline (on start / on disconnect / on shutdown).</summary>
         [Header("Scene Management")]
         [Scene]
@@ -290,6 +297,10 @@ void SetupServer()
             NetworkServer.disconnectInactiveTimeout = disconnectInactiveTimeout;
             NetworkServer.exceptionsDisconnect = exceptionsDisconnect;
 
+            // Setup reuseable network IDs
+            NetworkIdentity.reuseNetworkIds = reuseNetworkIds;
+            NetworkIdentity.reuseDelay = reuseDelay;
+
             if (runInBackground)
                 Application.runInBackground = true;
 

Assets/Mirror/Editor/NetworkInformationPreview.cs

@@ -113,6 +113,8 @@ public override void OnPreviewGUI(Rect r, GUIStyle background)
 
             Y = DrawObservers(identity, initialX, Y);
 
+            Y = DrawNetworkIDQueue(initialX, Y);
+
             _ = DrawOwner(identity, initialX, Y);
 
         }
@@ -193,6 +195,25 @@ float DrawObservers(NetworkIdentity identity, float initialX, float Y)
             return Y;
         }
 
+        float DrawNetworkIDQueue(float initialX, float Y)
+        {
+            if (NetworkIdentity.netIdQueue.Count > 0)
+            {
+                Rect netIdRect = new Rect(initialX, Y + 10, 200, 20);
+                GUI.Label(netIdRect, new GUIContent("Network ID Queue"), styles.labelStyle);
+                netIdRect.x += 20;
+                netIdRect.y += netIdRect.height;
+                foreach (var entry in NetworkIdentity.netIdQueue)
+                {
+                    GUI.Label(netIdRect, $"[{entry.reusableNetId}] {entry.timeAvailable:0.000}", styles.componentName);
+                    netIdRect.y += netIdRect.height;
+                    Y = netIdRect.y;
+                }
+            }
+
+            return Y;
+        }
+
         float DrawOwner(NetworkIdentity identity, float initialX, float Y)
         {
             if (identity.connectionToClient != null)