Restore original behavior

The doc says that fair locks show slower (often much slower) throughput.
Considering the nature of this class, higher throughput may be more important than fairness here.

Author: harawata

src/main/java/org/apache/ibatis/datasource/pooled/PooledDataSource.java

@@ -24,6 +24,8 @@
 import java.sql.Statement;
 import java.util.Properties;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Logger;
 
@@ -43,7 +45,6 @@ public class PooledDataSource implements DataSource {
   private static final Log log = LogFactory.getLog(PooledDataSource.class);
 
   private final PoolState state = new PoolState(this);
-  private final ReentrantLock fairLock = new ReentrantLock(true);
 
   private final UnpooledDataSource dataSource;
 
@@ -59,6 +60,9 @@ public class PooledDataSource implements DataSource {
 
   private int expectedConnectionTypeCode;
 
+  private Lock lock = new ReentrantLock();
+  private Condition condition = lock.newCondition();
+
   public PooledDataSource() {
     dataSource = new UnpooledDataSource();
   }
@@ -331,8 +335,8 @@ public int getPoolPingConnectionsNotUsedFor() {
    * Closes all active and idle connections in the pool.
    */
   public void forceCloseAll() {
+    lock.lock();
     try {
-      fairLock.lock();
       expectedConnectionTypeCode = assembleConnectionTypeCode(dataSource.getUrl(), dataSource.getUsername(), dataSource.getPassword());
       for (int i = state.activeConnections.size(); i > 0; i--) {
         try {
@@ -363,9 +367,7 @@ public void forceCloseAll() {
         }
       }
     } finally {
-      if (fairLock.isLocked()) {
-        fairLock.unlock();
-      }
+      lock.unlock();
     }
     if (log.isDebugEnabled()) {
       log.debug("PooledDataSource forcefully closed/removed all connections.");
@@ -381,8 +383,9 @@ private int assembleConnectionTypeCode(String url, String username, String passw
   }
 
   protected void pushConnection(PooledConnection conn) throws SQLException {
+
+    lock.lock();
     try {
-      fairLock.lock();
       state.activeConnections.remove(conn);
       if (conn.isValid()) {
         if (state.idleConnections.size() < poolMaximumIdleConnections && conn.getConnectionTypeCode() == expectedConnectionTypeCode) {
@@ -398,9 +401,7 @@ protected void pushConnection(PooledConnection conn) throws SQLException {
           if (log.isDebugEnabled()) {
             log.debug("Returned connection " + newConn.getRealHashCode() + " to pool.");
           }
-          if (fairLock.isLocked()) {
-            fairLock.unlock();
-          }
+          condition.signal();
         } else {
           state.accumulatedCheckoutTime += conn.getCheckoutTime();
           if (!conn.getRealConnection().getAutoCommit()) {
@@ -419,9 +420,7 @@ protected void pushConnection(PooledConnection conn) throws SQLException {
         state.badConnectionCount++;
       }
     } finally {
-      if (fairLock.isLocked()) {
-        fairLock.unlock();
-      }
+      lock.unlock();
     }
   }
 
@@ -432,8 +431,8 @@ private PooledConnection popConnection(String username, String password) throws
     int localBadConnectionCount = 0;
 
     while (conn == null) {
+      lock.lock();
       try {
-        fairLock.lock();
         if (!state.idleConnections.isEmpty()) {
           // Pool has available connection
           conn = state.idleConnections.remove(0);
@@ -491,7 +490,7 @@ private PooledConnection popConnection(String username, String password) throws
                   log.debug("Waiting as long as " + poolTimeToWait + " milliseconds for connection.");
                 }
                 long wt = System.currentTimeMillis();
-                fairLock.tryLock(poolTimeToWait, TimeUnit.MILLISECONDS);
+                condition.await(poolTimeToWait, TimeUnit.MILLISECONDS);
                 state.accumulatedWaitTime += System.currentTimeMillis() - wt;
               } catch (InterruptedException e) {
                 // set interrupt flag
@@ -529,9 +528,7 @@ private PooledConnection popConnection(String username, String password) throws
           }
         }
       } finally {
-        if (fairLock.isLocked()) {
-          fairLock.unlock();
-        }
+        lock.unlock();
       }
 
     }