add async load on logic option

plugin/src/main/java/com/denizenscript/denizen/Denizen.java

@@ -429,6 +429,7 @@ public void run() {
         if (!PlayerFlagHandler.dataFolder.exists()) {
             PlayerFlagHandler.dataFolder.mkdir();
         }
+        Bukkit.getPluginManager().registerEvents(new PlayerFlagHandler(), this);
         new BukkitRunnable() {
             @Override
             public void run() {

plugin/src/main/java/com/denizenscript/denizen/utilities/Settings.java

@@ -86,6 +86,7 @@ public static void refillCache() {
         cache_warningRate = config.getLong("Tags.Warning rate", 10000);
         cache_packetInterception = config.getBoolean("Packets.Interception", true);
         PlayerFlagHandler.cacheTimeoutSeconds = config.getLong("Saves.Offline player cache timeout", 300);
+        PlayerFlagHandler.asyncPreload = config.getBoolean("Saves.Load async on login", true);
     }
 
     private static boolean cache_showDebug = true, cache_overrideHelp, cache_useDefaultScriptPath,

plugin/src/main/java/com/denizenscript/denizen/utilities/flags/PlayerFlagHandler.java

@@ -218,5 +218,26 @@ public static void saveFlags(UUID id, String flagData) {
             Debug.echoError(ex);
         }
     }
+
+    @EventHandler
+    public void onPlayerLogin(AsyncPlayerPreLoginEvent event) {
+        if (!asyncPreload) {
+            return;
+        }
+        UUID id = event.getUniqueId();
+        if (!Bukkit.isPrimaryThread()) {
+            Future<Future> future = Bukkit.getScheduler().callSyncMethod(Denizen.getInstance(), () -> {
+                return loadAsync(id);
+            });
+            try {
+                Future newFuture = future.get(15, TimeUnit.SECONDS);
+                if (newFuture != null) {
+                    newFuture.get(15, TimeUnit.SECONDS);
+                }
+            }
+            catch (Throwable ex) {
+                Debug.echoError(ex);
+            }
+        }
     }
 }

plugin/src/main/resources/config.yml

@@ -182,6 +182,8 @@ Saves:
   # How long (in seconds) before the offline player flag cache times out.
   # Set to -1 to keep offline player flags loaded perpetually, or to 0 to never cache.
   Offline player cache timeout: 300
+  # When set to 'true', player data will be loaded offthread during the login sequence, to avoid adding load to the server while players join.
+  Load async on login: true
 
 Packets:
   # Whether to allow Denizen to intercept packets from and to player clients.