Improve memory resilience with Configurate (#6266)

Hopefully should cut down on memory usage with configurate.

Closes #6118

Author: JRoy

Essentials/src/main/java/com/earth2me/essentials/Essentials.java

@@ -45,6 +45,7 @@
 import com.earth2me.essentials.utils.VersionUtil;
 import io.papermc.lib.PaperLib;
 import net.ess3.api.Economy;
+import com.earth2me.essentials.config.EssentialsConfiguration;
 import net.ess3.api.IEssentials;
 import net.ess3.api.IItemDb;
 import net.ess3.api.IJails;
@@ -570,6 +571,8 @@ public void onDisable() {
         Trade.closeLog();
         getUsers().shutdown();
 
+        EssentialsConfiguration.shutdownExecutor();
+
         HandlerList.unregisterAll(this);
     }
 

Essentials/src/main/java/com/earth2me/essentials/config/ConfigurationSaveTask.java

@@ -6,34 +6,32 @@
 import org.spongepowered.configurate.yaml.YamlConfigurationLoader;
 
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Supplier;
 import java.util.logging.Level;
 
 public class ConfigurationSaveTask implements Runnable {
     private final YamlConfigurationLoader loader;
-    private final CommentedConfigurationNode node;
+    private final Supplier<CommentedConfigurationNode> nodeSupplier;
     private final AtomicInteger pendingWrites;
 
-    public ConfigurationSaveTask(final YamlConfigurationLoader loader, final CommentedConfigurationNode node, final AtomicInteger pendingWrites) {
+    public ConfigurationSaveTask(final YamlConfigurationLoader loader, final Supplier<CommentedConfigurationNode> nodeSupplier, final AtomicInteger pendingWrites) {
         this.loader = loader;
-        this.node = node;
+        this.nodeSupplier = nodeSupplier;
         this.pendingWrites = pendingWrites;
     }
 
     @Override
     public void run() {
-        synchronized (loader) {
-            // Check if there are more writes in queue.
-            // If that's the case, we shouldn't bother writing data which is already out-of-date.
-            if (pendingWrites.get() > 1) {
-                pendingWrites.decrementAndGet();
-            }
+        if (pendingWrites.decrementAndGet() > 0) {
+            return;
+        }
 
+        synchronized (loader) {
             try {
+                final CommentedConfigurationNode node = nodeSupplier.get();
                 loader.save(node);
             } catch (ConfigurateException e) {
                 Essentials.getWrappedLogger().log(Level.SEVERE, e.getMessage(), e);
-            } finally {
-                pendingWrites.decrementAndGet();
             }
         }
     }

Essentials/src/main/java/com/earth2me/essentials/config/EssentialsConfiguration.java

@@ -43,15 +43,15 @@
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.Level;
 
 import static com.earth2me.essentials.I18n.tlLiteral;
 
 public class EssentialsConfiguration {
-    private static final ExecutorService EXECUTOR_SERVICE = Executors.newSingleThreadExecutor();
+    private static volatile ExecutorService EXECUTOR_SERVICE = Executors.newSingleThreadExecutor();
     private static final ObjectMapper.Factory MAPPER_FACTORY = ObjectMapper.factoryBuilder()
             .addProcessor(DeleteOnEmpty.class, (data, value) -> new DeleteOnEmptyProcessor())
             .addProcessor(DeleteIfIncomplete.class, (data, value) -> new DeleteIfIncompleteProcessor())
@@ -462,21 +462,50 @@ public synchronized void save() {
 
     public synchronized void blockingSave() {
         try {
-            delaySave().get();
+            delaySave();
+            getExecutor().submit(() -> {}).get();
         } catch (final InterruptedException | ExecutionException e) {
             Essentials.getWrappedLogger().log(Level.SEVERE, e.getMessage(), e);
         }
     }
 
-    private Future<?> delaySave() {
+    private void delaySave() {
         if (saveHook != null) {
             saveHook.run();
         }
 
-        final CommentedConfigurationNode node = configurationNode.copy();
-
         pendingWrites.incrementAndGet();
+        try {
+            getExecutor().submit(new ConfigurationSaveTask(loader, () -> configurationNode.copy(), pendingWrites));
+        } catch (RejectedExecutionException rex) {
+            try {
+                synchronized (loader) {
+                    loader.save(configurationNode.copy());
+                }
+            } catch (ConfigurateException e) {
+                Essentials.getWrappedLogger().log(Level.SEVERE, e.getMessage(), e);
+            } finally {
+                pendingWrites.decrementAndGet();
+            }
+        }
+    }
 
-        return EXECUTOR_SERVICE.submit(new ConfigurationSaveTask(loader, node, pendingWrites));
+    public static void shutdownExecutor() {
+        final ExecutorService exec = EXECUTOR_SERVICE;
+        exec.shutdown();
+        try {
+            if (!exec.awaitTermination(5, java.util.concurrent.TimeUnit.SECONDS)) {
+                exec.shutdownNow();
+            }
+        } catch (InterruptedException ignored) {
+            exec.shutdownNow();
+        }
+    }
+
+    private static synchronized ExecutorService getExecutor() {
+        if (EXECUTOR_SERVICE == null || EXECUTOR_SERVICE.isShutdown() || EXECUTOR_SERVICE.isTerminated()) {
+            EXECUTOR_SERVICE = Executors.newSingleThreadExecutor();
+        }
+        return EXECUTOR_SERVICE;
     }
 }