Improve performance of chunk loaded metric and offline player count

src/main/java/de/sldk/mc/collectors/LoadedChunksCollector.java

@@ -0,0 +1,57 @@
+package de.sldk.mc.collectors;
+
+import org.bukkit.Bukkit;
+import org.bukkit.World;
+import org.bukkit.event.EventHandler;
+import org.bukkit.event.Listener;
+import org.bukkit.event.world.ChunkLoadEvent;
+import org.bukkit.event.world.ChunkUnloadEvent;
+import org.bukkit.event.world.WorldUnloadEvent;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class LoadedChunksCollector implements Listener {
+
+    private final Map<String, Integer> loadedChunksTotalMap = new HashMap<>();
+
+    @EventHandler
+    public void onChunkLoad(ChunkLoadEvent event) {
+        World world = event.getWorld();
+        Integer currentCount = loadedChunksTotalMap.get(world.getName());
+        if (currentCount == null) {
+            loadedChunksTotalMap.put(world.getName(), world.getLoadedChunks().length);
+        }
+        else {
+            loadedChunksTotalMap.put(world.getName(), currentCount + 1);
+        }
+    }
+
+    @EventHandler
+    public void onChunkUnload(ChunkUnloadEvent event) {
+        World world = event.getWorld();
+        Integer currentCount = loadedChunksTotalMap.get(world.getName());
+        if (currentCount == null) {
+            loadedChunksTotalMap.put(world.getName(), world.getLoadedChunks().length);
+        }
+        else {
+            loadedChunksTotalMap.put(world.getName(), currentCount - 1);
+        }
+    }
+
+    @EventHandler
+    public void onWorldUnload(WorldUnloadEvent event) {
+        World world = event.getWorld();
+        loadedChunksTotalMap.remove(world.getName());
+    }
+
+    public int getLoadedChunkTotal(String worldName) {
+        return loadedChunksTotalMap.computeIfAbsent(worldName, k -> {
+            World world = Bukkit.getWorld(worldName);
+            if (world == null) {
+                return 0;
+            }
+            return world.getLoadedChunks().length;
+        });
+    }
+}

src/main/java/de/sldk/mc/tps/TpsCollector.java → src/main/java/de/sldk/mc/collectors/TpsCollector.java

@@ -1,4 +1,4 @@
-package de.sldk.mc.tps;
+package de.sldk.mc.collectors;
 
 import java.util.LinkedList;
 import java.util.function.Supplier;

src/main/java/de/sldk/mc/metrics/LoadedChunks.java

@@ -1,7 +1,9 @@
 package de.sldk.mc.metrics;
 
+import de.sldk.mc.collectors.LoadedChunksCollector;
 import io.prometheus.client.Gauge;
 import org.bukkit.World;
+import org.bukkit.event.HandlerList;
 import org.bukkit.plugin.Plugin;
 
 public class LoadedChunks extends WorldMetric {
@@ -12,17 +14,31 @@ public class LoadedChunks extends WorldMetric {
             .labelNames("world")
             .create();
 
+    private final LoadedChunksCollector loadedChunksCollector = new LoadedChunksCollector();
+
     public LoadedChunks(Plugin plugin) {
         super(plugin, LOADED_CHUNKS);
     }
 
+    @Override
+    public void enable() {
+        super.enable();
+        getPlugin().getServer().getPluginManager().registerEvents(loadedChunksCollector, getPlugin());
+    }
+
+    @Override
+    public void disable() {
+        super.disable();
+        HandlerList.unregisterAll(loadedChunksCollector);
+    }
+
     @Override
     protected void clear() {
 		LOADED_CHUNKS.clear();
     }
 
     @Override
     public void collect(World world) {
-        LOADED_CHUNKS.labels(world.getName()).set(world.getLoadedChunks().length);
+        LOADED_CHUNKS.labels(world.getName()).set(loadedChunksCollector.getLoadedChunkTotal(world.getName()));
     }
 }

src/main/java/de/sldk/mc/metrics/PlayersTotal.java

@@ -19,4 +19,9 @@ public PlayersTotal(Plugin plugin) {
     public void doCollect() {
         PLAYERS.set(Bukkit.getOfflinePlayers().length);
     }
+
+    @Override
+    public boolean isAsyncCapable() {
+        return true;
+    }
 }

src/main/java/de/sldk/mc/metrics/Tps.java

@@ -1,6 +1,6 @@
 package de.sldk.mc.metrics;
 
-import de.sldk.mc.tps.TpsCollector;
+import de.sldk.mc.collectors.TpsCollector;
 import io.prometheus.client.Gauge;
 import org.bukkit.Bukkit;
 import org.bukkit.plugin.Plugin;

src/test/java/de/sldk/mc/tps/TpsCollectorTest.java → src/test/java/de/sldk/mc/collectors/TpsCollectorTest.java

@@ -1,4 +1,4 @@
-package de.sldk.mc.tps;
+package de.sldk.mc.collectors;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.when;