Delayed write to file (experimental)

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

@@ -9,6 +9,9 @@ import java.nio.charset.Charset;
 import java.nio.charset.CharsetDecoder;
 import java.nio.charset.CoderResult;
 import java.util.*;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import org.bukkit.*;
@@ -24,21 +27,27 @@ import org.bukkit.util.Vector;
 public class EssentialsConf extends YamlConfiguration
 {
 	private static final Logger LOGGER = Logger.getLogger("Minecraft");
-	private transient File configFile;
+	private final File configFile;
-	private transient String templateName = null;
+	private String templateName = null;
-	private transient Class<?> resourceClass = EssentialsConf.class;
+	private Class<?> resourceClass = EssentialsConf.class;
 	private static final Charset UTF8 = Charset.forName("UTF-8");
+	private static final ExecutorService EXECUTOR_SERVICE = Executors.newSingleThreadExecutor();
+	private final AtomicInteger pendingDiskWrites = new AtomicInteger(0);
 
 	public EssentialsConf(final File configFile)
 	{
 		super();
-		this.configFile = configFile;
+		this.configFile = configFile.getAbsoluteFile();
 	}
 	private final byte[] bytebuffer = new byte[1024];
 
 	public synchronized void load()
 	{
-		configFile = configFile.getAbsoluteFile();
+		if (pendingDiskWrites.get() != 0)
+		{
+			LOGGER.log(Level.INFO, "File " + configFile + " not read, because it's not yet written to disk.");
+			return;
+		}
 		if (!configFile.getParentFile().exists())
 		{
 			if (!configFile.getParentFile().mkdirs())
@@ -241,13 +250,12 @@ public class EssentialsConf extends YamlConfiguration
 	@Override
 	public synchronized void save(final File file) throws IOException
 	{
+		//long startTime = System.nanoTime();
 		if (file == null)
 		{
 			throw new IllegalArgumentException("File cannot be null");
 		}
 
-		Files.createParentDirs(file);
-
 		final String data = saveToString();
 
 		if (data.length() == 0)
@@ -255,6 +263,45 @@ public class EssentialsConf extends YamlConfiguration
 			return;
 		}
 
+		pendingDiskWrites.incrementAndGet();
+
+		EXECUTOR_SERVICE.submit(new WriteRunner(configFile, data, pendingDiskWrites));
+
+		//LOGGER.log(Level.INFO, configFile + " prepared for writing in " + (System.nanoTime() - startTime) + " nsec.");
+	}
+
+
+	private static class WriteRunner implements Runnable
+	{
+		private final File configFile;
+		private final String data;
+		private final AtomicInteger pendingDiskWrites;
+
+		private WriteRunner(final File configFile, final String data, final AtomicInteger pendingDiskWrites)
+		{
+			this.configFile = configFile;
+			this.data = data;
+			this.pendingDiskWrites = pendingDiskWrites;
+		}
+
+		@Override
+		public void run()
+		{
+			//long startTime = System.nanoTime();
+			synchronized (configFile)
+			{
+				if (pendingDiskWrites.get() > 1)
+				{
+					// Writes can be skipped, because they are stored in a queue (in the executor). 
+					// Only the last is actually written.
+					pendingDiskWrites.decrementAndGet();
+					//LOGGER.log(Level.INFO, configFile + " skipped writing in " + (System.nanoTime() - startTime) + " nsec.");
+					return;
+				}
+				try
+				{
+					Files.createParentDirs(configFile);
+
 					if (!configFile.exists())
 					{
 						try
@@ -263,16 +310,18 @@ public class EssentialsConf extends YamlConfiguration
 							if (!configFile.createNewFile())
 							{
 								LOGGER.log(Level.SEVERE, _("failedToCreateConfig", configFile.toString()));
+								return;
 							}
 						}
 						catch (IOException ex)
 						{
 							LOGGER.log(Level.SEVERE, _("failedToCreateConfig", configFile.toString()), ex);
+							return;
 						}
 					}
 
 
-		final OutputStreamWriter writer = new OutputStreamWriter(new FileOutputStream(file), UTF8);
+					final OutputStreamWriter writer = new OutputStreamWriter(new FileOutputStream(configFile), UTF8);
 
 					try
 					{
@@ -283,6 +332,18 @@ public class EssentialsConf extends YamlConfiguration
 						writer.close();
 					}
 				}
+				catch (IOException e)
+				{
+					LOGGER.log(Level.SEVERE, e.getMessage(), e);
+				}
+				finally
+				{
+					//LOGGER.log(Level.INFO, configFile + " written to disk in " + (System.nanoTime() - startTime) + " nsec.");
+					pendingDiskWrites.decrementAndGet();
+				}
+			}
+		}
+	}
 
 	public boolean hasProperty(final String path)
 	{