From e75c4295de15e2e8a9825b8e21008bde08b761b0 Mon Sep 17 00:00:00 2001
From: Robin Kupper <robbzkupper@web.de>
Date: Sun, 26 Jun 2011 20:30:26 +0200
Subject: [PATCH] Fixed deadlock in connection pool.

---
 src/de/diddiz/LogBlock/LogBlock.java        |  3 +-
 src/de/diddiz/util/MySQLConnectionPool.java | 53 +++++++++++++--------
 2 files changed, 35 insertions(+), 21 deletions(-)

diff --git a/src/de/diddiz/LogBlock/LogBlock.java b/src/de/diddiz/LogBlock/LogBlock.java
index 286dfcb..0f95e9a 100644
--- a/src/de/diddiz/LogBlock/LogBlock.java
+++ b/src/de/diddiz/LogBlock/LogBlock.java
@@ -4,7 +4,6 @@ import static de.diddiz.util.Utils.downloadIfNotExists;
 import java.io.File;
 import java.net.URL;
 import java.sql.Connection;
-import java.sql.SQLException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Timer;
@@ -181,7 +180,7 @@ public class LogBlock extends JavaPlugin
 	public Connection getConnection() {
 		try {
 			return pool.getConnection();
-		} catch (final SQLException ex) {
+		} catch (final Exception ex) {
 			log.log(Level.SEVERE, "[LogBlock] Error while fetching connection", ex);
 			return null;
 		}
diff --git a/src/de/diddiz/util/MySQLConnectionPool.java b/src/de/diddiz/util/MySQLConnectionPool.java
index 80db572..d31d666 100644
--- a/src/de/diddiz/util/MySQLConnectionPool.java
+++ b/src/de/diddiz/util/MySQLConnectionPool.java
@@ -21,6 +21,10 @@ import java.util.Enumeration;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Vector;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 public class MySQLConnectionPool implements Closeable
 {
@@ -29,6 +33,7 @@ public class MySQLConnectionPool implements Closeable
 	private final Vector<JDCConnection> connections;
 	private final ConnectionReaper reaper;
 	private final String url, user, password;
+	private final Lock lock = new ReentrantLock();
 
 	public MySQLConnectionPool(String url, String user, String password) throws ClassNotFoundException {
 		Class.forName("com.mysql.jdbc.Driver");
@@ -41,41 +46,51 @@ public class MySQLConnectionPool implements Closeable
 	}
 
 	@Override
-	public synchronized void close() {
+	public void close() {
+		lock.lock();
 		final Enumeration<JDCConnection> conns = connections.elements();
 		while (conns.hasMoreElements()) {
 			final JDCConnection conn = conns.nextElement();
 			connections.remove(conn);
 			conn.terminate();
 		}
+		lock.unlock();
 	}
 
-	public synchronized Connection getConnection() throws SQLException {
-		JDCConnection conn;
-		for (int i = 0; i < connections.size(); i++) {
-			conn = connections.get(i);
-			if (conn.lease()) {
-				if (conn.isValid())
-					return conn;
-				connections.remove(conn);
-				conn.terminate();
+	public Connection getConnection() throws SQLException, InterruptedException, TimeoutException {
+		if (!lock.tryLock(100, TimeUnit.MILLISECONDS))
+			throw new TimeoutException();
+		try {
+			JDCConnection conn;
+			for (int i = 0; i < connections.size(); i++) {
+				conn = connections.get(i);
+				if (conn.lease()) {
+					if (conn.isValid())
+						return conn;
+					connections.remove(conn);
+					conn.terminate();
+				}
 			}
+			conn = new JDCConnection(DriverManager.getConnection(url, user, password));
+			conn.lease();
+			if (!conn.isValid()) {
+				conn.terminate();
+				throw new SQLException("Failed to validate a brand new connection");
+			}
+			connections.add(conn);
+			return conn;
+		} finally {
+			lock.unlock();
 		}
-		conn = new JDCConnection(DriverManager.getConnection(url, user, password));
-		conn.lease();
-		if (!conn.isValid()) {
-			conn.terminate();
-			throw new SQLException("Failed to validate a brand new connection");
-		}
-		connections.add(conn);
-		return conn;
 	}
 
-	private synchronized void reapConnections() {
+	private void reapConnections() {
+		lock.lock();
 		final long stale = System.currentTimeMillis() - timeToLive;
 		for (final JDCConnection conn : connections)
 			if (conn.inUse() && stale > conn.getLastUse() && !conn.isValid())
 				connections.remove(conn);
+		lock.unlock();
 	}
 
 	private class ConnectionReaper extends Thread